text:
Singapore Introduces New Healthcare Reform Plan
https://www.aseanbriefing.com/news/singapore-introduces-new-healthcare-reform-p…
aseanbriefing.com (21.10.2022) Singapore has recently announced a new healthcare reform plan that will shift the country's healthcare strategy towards preventive care. The program is called Healthier SG and aims to provide a family physician and one health plan for every resident. The hope is that family doctors will develop strong relationships with their patients and play a more prominent role in preventive healthcare. The change in strategy comes because Singapore is fast becoming an aging society, with one in four residents aged 65 and above by 2030.
How AI and robots are caring for the elderly in Taiwan's ageing society
https://govinsider.asia/health/how-ai-and-robots-are-caring-for-the-elderly-in-…
GovInsider (April 2022) Yet, advancements in healthcare and sanitation standards are helping adults live longer than ever before. Taiwan, in particular, is estimated to become a super-aged society by 2025, with one in five being over 65 years old, said Dr Jenny Su Huey-Jen, President of the National Cheng Kung University (NCKU). To better support the seniors in its population, Taiwan is building a new geriatric hospital. Su shares how this hospital will better provide healthcare services to an ageing population.
Digital Technologies for Government-Supported Health Insurance Systems in Asia and the Pacific
https://www.adb.org/publications/digital-technologies-government-supported-heal…
Asian Development Bank (December 2021) Examples from low- and middle-income countries in the region and beyond are drawn to demonstrate how digital solutions have improved health insurance management and administration. To support decision-making on potential investments, the report identifies key success factors for integrating new technologies into public health insurance schemes.
Technology and Universal Health Coverage: Examining the role of digital health
https://jogh.org/2021/jogh-11-16006
JOGH (20.11.2021) While there is tremendous promise to leverage technology for UHC, it will require smart, context-specific policies and programming with ample flexibility to adapt as needs and opportunities change – and with robust safeguards to protect privacy, data security, and equity. The health sector, by its very nature of being data intensive, lends itself to the use of technology for analytics to improve health outcomes, respond to public health crises, and efficiently and equitably allocate resources.
Moroccan government plans to expand its social protection programme
https://atalayar.com/index.php/en/content/moroccan-government-plans-expand-its-…
atalayar.com (03.01.2022) This new plan will strengthen and develop several programmes in the areas of social assistance, improving governance, as well as launching new carve-outs that signify a reform of the targeting system. Also, this project aims to diversify and expand the support mechanisms for the most vulnerable groups of society, which in the case of retirees for example, will extend their health and retirement coverage. The government also plans to develop a system of compensation for those who have lost their jobs.
Leftist millennial Gabriel Boric, that vowed to reform pensions for the poor, is elected president of Chile.
https://www.pensionpolicyinternational.com/leftist-millennial-gabriel-boric-tha…
- Pension Policy International (20.12.2021) Leftist lawmaker Gabriel Boric, 35, on Sunday became Chile's youngest-ever president on promises of installing a "welfare state" in one of the world's most unequal countries.


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Dau.I sent me two books for my bday two weeks ago: I've already told you TMI about Feynman and Leonard's testicles. The other [super wonderful] book was The Youngest Science: notes of a medicine watcher by Lewis Thomas. Thomas was, according to The Wik, "an American physician, poet, etymologist, essayist, administrator, educator, policy advisor, and researcher". I don't think that evidence of multiple skills makes him a polymath, let alone a genius, in the way that Murray Gell-Mann or Jean-Baptiste Biot or JBS Haldane, could be so classified. administrator, educator, policy advisor, makes him look a bit ploddy; poet, etymologist, essayist, a bit butterfly. Don't dismiss him until you've read his 1974 collection of essays The Lives of the Cell: notes of a biology watcher which is a best-of from his commissioned column for the New England Journal of Medicine NEJM. That book came out just as I started college and the sequel The Medusa and the Snail (1979) was published just as I started graduate school. Both collections won prizes for inspiring youngsters to go into science. This was years before the world wide web, let alone blogs, so there were few enough avenues for putting down some thoughts on a range of topics and getting them published. The essay is a form I like very much: short enough to read at a sitting and long enough to develop some arguments that make you think.
The Youngest Science TYS is billed as Thomas's autobiography but it's really too sketchy to qualify for that. It's a series of themes and anecdotes which are co-terminous with the author's life but leave a lot of detail on the cutting room floor. Discarding the boring makes his life a bit more exciting. The key theme is how the practice of medicine has changed, changed utterly, since Thomas's GP father was struggling to make ends meet at the end of each month in the years before WWI. Young Thomas was never going down the GP route and went through a succession of academic, clinical and administrative positions all over the USA. One of the most striking differences between the work of medicine in 1933, when Thomas first started clumping the wards at dead of night, and 1983, when TYS was published, is the range of diseases were not but are now treatable. In the 1930s there were effective therapies for
lobar pneumonia [type-specific anti-pneumococcus antibodies; first type your pneumococcus from a sputum sample as quickly and reliably as possible]
diabetic coma [a dribble of insulin and intravenous fluids]
acute heart failure [bleeding (!) to reduce blood-pressure; digitalis as in tincture of foxglove Digitalis purpurea leaves to ooomph the heart muscle; oxygen]
syphilis [bismuth, arsenic compounds and mercury . . . and a lot of time]
and that's about it. The first three required speedy and accurate diagnosis if the treatment was to be successful.
All the rest of hospitals' work was 'simply custodial' patients would only be rolled into hospital if they were really sick but there was nothing really to do except "waiting for the illness to finish itself off one way or the other". My father developed pneumonia after being taken for a bracing winter swim in the Irish Sea while at boarding school in 1929. The school called his mother, who sat by his bedside for ten days mopping his brow and talking to him until the fever broke and he started smiling again. His immune system had finally triumphed over the invasive Pneumococci. His mother probably made a difference because of the untapped and poorly understood power of PNI psycho-nearo-immunology [bloboprev]. According the Thomas "If being in hospital made a difference, it was mostly the difference produced by warmth, shelter, food and attentive, friendly care and the matchless skill of the nurses providing these things". Certainly in those days, the nurses saved as many lives as the doctors. And nobody was in it for the money.
Now it seems that it is all about the money. If you're a doctor prescribing a medicine which costs €160,000/yr, you'd be tempted to think "I'll have $ome of that"; you wouldn't be human or have a mortgage if that didn't cross your mind. The Brother spent long years making quality TV commercials for a living. The cost of 30 seconds of airtime in the evening was a king's ransom, just to play: so the companies tended to invest equally heavily in production values, and The Brother and his company (and the key-grip, the best boy, the continuity department and make-up) got a piece of the action.
In a life-time of science, I've had three good ideas and one of them turned out to be wrong and we got scooped on one of the others, so it was never published under my name. It's been a bit like that for Dr Thomas and this book of essays written in retirement allows him to put down a marker on a couple of those unpublishable hunches: possibly to intrigue a youngster to take up the fading scent and keep up the hunt for a solution. One of these is the observation that a peculiar sort of arthritis in pigs is definitely triggered by mycoplasma bacteria [bloboprev] and that both mycoplasma infestation and the 'auto-immune' disease rheumatoid arthritis are both susceptible to treatment with gold salts. Nobody has ever been able to culture mycoplasmas, or indeed any potentially causative microbe, from RA inflamed joint tissue. But the list of bacteria that have never been grown on a Petri dish far far exceeds those that have. I'm with, or at least behind, Thomas on this sort of idea. We will eventually find microbial infection - virus, bacteria or protozoan - acting as a trigger in all autoimmune diseases.
TYS is more than 30 years old, so parts of it are out of date and superseded, but as an inspiration for using science as a way of knowing & being open, curious, hard-working, stubborn and committed, it should be on the reading list for any favorite niece or nephew heading up to Med School.
I'll leave you with a final insight from Lewis Thomas "The future is too interesting and dangerous to be entrusted to any predictable, reliable agency." Which may remind you of JBS Haldane's: "I have no doubt that in reality the future will be vastly more surprising than anything I can imagine. Now my own suspicion is that the Universe is not only queerer than we suppose, but queerer than we can suppose."

redpajama_set_name: RedPajamaCommonCrawl


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Massachusetts House of Representatives' 2nd Bristol district in the United States is one of 160 legislative districts included in the lower house of the Massachusetts General Court. It covers part of Attleboro in Bristol County. Democrat Jim Hawkins of Attleboro has represented the district since 2018.

The current district geographic boundary overlaps with those of the Massachusetts Senate's Bristol and Norfolk and Norfolk, Bristol and Middlesex districts.

Representatives
 John Crane, circa 1858
 Daniel S. Cobb, circa 1859
 William Blanding Rogerson, circa 1888
 Kenneth W. Keith, circa 1920
 Albert E. Wood, circa 1951
 Edward Paul Coury, circa 1975
 Stephen Karol, circa 1994
 John Lepper, 1995–2009
 Bill Bowles, 2009–2011
 George T. Ross, 2011–2013
 Paul Heroux, January 5, 2013 – January 2, 2018
 Jim Hawkins, 2018-current

Former locales
The district previously covered:
 Easton, circa 1927
 Mansfield, circa 1872
 Norton, circa 1872

See also
 List of Massachusetts House of Representatives elections
 Other Bristol County districts of the Massachusetts House of Representatives: 1st, 3rd, 4th, 5th, 6th, 7th, 8th, 9th, 10th, 11th, 12th, 13th, 14th
 List of Massachusetts General Courts
 List of former districts of the Massachusetts House of Representatives

Images

References

External links
 Ballotpedia
  (State House district information based on U.S. Census Bureau's American Community Survey).

House
Government of Bristol County, Massachusetts

redpajama_set_name: RedPajamaWikipedia


San Zaccaria (Ravenna), 4 October 2016 - A few hours before the end of the first day of the championship the staff available to Gianluca Nardozza continues to expand and this time it does so with an absolute first time in Ireland. The red and white society has in fact started the practices for the membership of the defender Shauna Margaret Peare, who for some time was training under the orders of Mr. Nardozza.
Shauna, born in Dublin on 10 September 1992, started playing football when she was just six years old on her city's team. Since then, his career has been a crescendo that brought her to the American university championships and to Texas with the Brownsville team.
AGSM VERONA FIRST ALSO IN FAIR PLAY!
After the conquest of the Scudetto comes another important recognition for the Agsm Verona. The Gialloblù club for the second consecutive season has in fact won the Discipline Cup, according to the official ranking published by Federcalcio.
The team from Verona was the most correct in the Serie A championship with only 5,35 penalty points ahead of Tavagnacco (5,40), Pordenone (5,80) and Brescia (6,80). In the last position we find the relegated Cuneo with 31,85 points, preceded by Bari, Florence and Torres.
The ranking takes into account the warnings, expulsions and disqualifications imposed on athletes, technicians and managers, but also the score achieved by the companies regarding the correctness of the public and the behavior held in the races of the top league.
The Gialloblù club wins the record in the Fair-Play for the sixth time. In the company's gold list, in fact, the achievements in the sports seasons include 1998 / 99, 2006 / 07, 2008 / 09, 2009 / 10, 2013 / 14 and finally 2014 / 15.
President Bressan, mister Longega and Carlotta Baldo received from the Veneto Region and awarded by the president of the Ruffato Regional Council for the conquest of the tricolor.
They are already in the fifth Scudetto and now look at the UEFA Women's Champions League: the girls of the Agram Verona, 2014-2015 Italian champions, received this Wednesday 3 June at "Palazzo Ferro-Fini" in Venice the homage of the President of the Regional Council of the Veneto Clodovaldo Ruffato.
"You are an example of commitment, tenacity and success that honors the Veneto sport and the young generations", emphasized Ruffato, highlighting the test of character, the effort and perseverance shown by the girls of Verona football, succeeding to combine school or work with daily training, without benefiting from the high rewards reserved for professional colleagues.
As is customary for the past four years, the Cuneo Calcio Femminile concludes the season of the youth sector by organizing a free stage reserved for girls born in the years 2000-2001-2002-2003-2004-2005.
SAN ZACCARIA (IZ) - San Zaccaria will start again with Marinella Piolanti on the bench in the 2015 / 2016 season. It is therefore official to reconfirm full marks of the coach who in the last four months has led, in tandem with the sports director Lorenzini, the red and white team to a stratospheric salvation in Serie A. A salvation from applause achieved thanks to a continuity of excellent results for a newly promoted first experience in the category with 14 points collected in the last 8 days and the final climax in the play-off play-off won in comeback against the Riviera of Romagna away, decided by the goals of Barbieri and Galletti in the second half: "Piolanti has proved an excellent coach, able to manage and grow the group in the second round.
The 27-2014 season of the Cuneo Calcio Femminile officially ended on Wednesday 15 May. The girls of Mr. Petruzzelli last night, in fact, supported the last training session with a friendly against the Alba Women's team.
THE BEST DEFENSE ... IS THE DEFENSE!
For many the best defense is the attack, but in football, you know, the opposite holds true ... 1 Rule number: do not take a goal!
And the extra weapon of Res Rome was certainly the defense, with the Giallorossi who boast the second best defense of Italian women's football, calculating both the Italian Cup and the championship.
Pipitone and companions have undergone a total 24 goal (23 in the league and only one in the Cup), exactly the same as Verona and Mozzanica, and only one more than Brescia, which however played in the Italian Cup 2 races less.
Among the protagonists of the primacy of the Giallorossi the goalkeeper Rosalia Pipitone, already winner of the "Golden Girl" as best goalkeeper of last year, author of another great season to defend the Capitoline door. Among the insiders it is defined by everyone, together with the colleague Gritti del Mozzanica, the strongest door in the championship, even if strangely it has never been taken into consideration by the staff of the major national team.
Read more: THE BEST DEFENSE ... IS THE DEFENSE!
MILAN MARITIME - Romagna is still red-bones in Serie A. The San Zaccaria against all odds makes the company by stretching the Riviera di Romagna in the heard derby play out and signing a salvation masterpiece. This is still a big party for President Macori's company, one year after the historic promotion in the top flight; yesterday was written another indelible page of its history because the red and white was the only newly promoted to be saved, a goal deserved for a team that grew steadily during the arc of the championship and able to play it openly even at the with the big players in the group. And yesterday, in a stadium Dei Pini, crowded by many fans, came yet another demonstration of strength and character of the group led by the tandem Lorenzini-Piolanti. In the first fraction in fact the challenge was stuck on the tracks of balance with rare occasions on both sides: the only upheavals are Riviera shore with an attempt to high Caccamo (20 ') and a poisonous cross shot on punishment of Tucceri Cimini foiled in corner by Bonaventura (35 ').
MILAN MARITIME - The Riviera di Romagna comes down to hell, defeated by San Zaccaria in the derby salvation played at the Stadio "Dei Pini" in Milano Marittima: 2-1 the final in favor of the red and white training, at the end of a balanced challenge, with the first thrill at 6 'on the left wing of grass Galletti that was turned off at the bottom, then little to report until the final minutes of the first fraction, with the yellow-red-blue that responded to 35' with a free kick from three quarters Linda Tucceri Cimini to fish the inclusion of Kristina Erman on the far post, which came with a moment of delay to the winning deviation. The race was unlocked shortly after: percussion on the left of Patty Caccamo who returned to dribbling and was spread by Pondini for the penalty in favor of the landlord: Luisa Pugnali on the spot that kicked on the post, but Patty Caccamo collected the loose ball and with a lightning-fast right he carried the ball at the intersection of the poles (40 ').


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\section{Introduction}
The Galactic plane has been observed extensively over the past decades by different survey projects at multiple wavelengths in both continuum and spectral lines, from near infrared (e.g., UKIDSS\footnote{UKIRT Infrared Deep Sky Survey}, \citealt{lucas2008}; {\it Spitzer}/GLIMPSE\footnote{Galactic Legacy Infrared Midplane Survey Extraordinaire }, \citealt{benjamin2003,churchwell2009}, {\it Spitzer}/MIPSGAL\footnote{A 24 and 70 Micron Survey of the Inner Galactic Disk with MIPS}, \citealt{carey2009}, {\it Herschel}/Hi-GAL\footnote{{\it Herschel} Infrared GALactic plane survey}, \citealt{Molinari2010}), to (sub)mm (e.g., ATLASGAL\footnote{APEX Telescope Large Area Survey of the Galaxy}, BGPS\footnote{Bolocam Galactic Plane Survey}, GRS\footnote{The Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey}, MALT90\footnote{The Millimeter Astronomy Legacy Team Survey at 90 GHz}, MALT-45\footnote{The Millimetre Astronomer's Legacy Team - 45 GHz}, FUGIN\footnote{FOREST unbiased Galactic plane imaging survey with the Nobeyama 45 m telescope}, MWISP\footnote{The Milky Way Imaging Scroll Painting}, \citealt{schuller2009, rosolowsky2010, aguirre2011, csengeri2014, Jackson2006, Foster2011, Jordan2015, Umemoto2017, Su2019}), and radio wavelengths (e.g. MAGPIS\footnote{Multi-Array Galactic Plane Imaging Survey}, CORNISH\footnote{the Co-Ordinated Radio `N' Infrared Survey for High-mass star formation}, CGPS\footnote{The Canadian Galactic Plane Survey}, SGPS\footnote{The Southern Galactic Plane Survey}, VGPS\footnote{The VLA Galactic Plane Survey}, HOPS\footnote{The H$_2$O Southern Galactic Plane Survey}, Sino-German 6~cm survey, \citealt{helfand2006, hoare2012, Taylor2003, McClure2005, stil2006, Walsh2011, Sun2007}). These surveys provide vital data to study and understand the interstellar medium (ISM) in different phases: atomic, molecular, ionized gas, and dust. While many of the surveys have a high angular resolution ($\leq$~40$\arcsec$), the highest angular resolution 21~cm \ion{H}{i} line survey of the northern Galactic plane, VGPS \citep{stil2006}, has a resolution of only 60\arcsec, which makes it difficult to compare with the aforementioned surveys to study the phase transitions of the ISM.

We therefore initiated the \ion{H}{i}, OH, recombination line survey of the Milky Way (THOR\footnote{\url {http://www.mpia.de/thor/Overview.html}}; \citealt{beuther2016}). A large fraction of the Galactic plane in the first quadrant of the Milky Way ($l=14.0-67.4^\circ$ and $\lvert b \rvert \leq 1.25^\circ$) was observed with the {\it Karl G. Jansky} Very Large Array (VLA) in C-configuration. At $L$ Band, the WIDAR correlator at the VLA was set to cover the 21~cm \ion{H}{i} line, four OH transitions, a series of H$n\alpha$ radio recombination lines (RRLs; $n=151$ to 186), as well as eight 128~MHz wide continuum spectral windows (SPWs), simultaneously. With the C-configuration, we achieve an angular resolution of $<25$\arcsec\ to compare with existing surveys at a matching resolution. The main survey description and data release 1 ($l=14.0\degr-37.9\degr$, and $l=47.1\degr-51.2\degr$) is presented in \citet{beuther2016}. Here, we publish the remaining \ion{H}{i}, OH, and RRL data, including a whole new set of \ion{H}{i} data that combines the existing D-configuration and Green Bank Telescope (GBT) observations to recover the larger scale emission \citep{stil2006}. Scientifically, we focus on an overview of the new \ion{H}{i} data in this paper. The continuum emission, OH absorption and masers from the survey were studied and presented in \citet{Bihr2016}, \citet{Walsh2016}, \citet{rugel2018}, \citet{Wang2018}, and \citet{Beuther2019}. Additionally, \citet{anderson2017} identified 76 new Galactic supernova remnant (SNR) candidates with the continuum data. Using the THOR RRL data, \citet{Rugel2019} studied the feedback in W49A and suggest that star formation in W49A is potentially regulated by feedback-driven and re-collapsing shells.

Since the 1950s, the Galactic 21~cm \ion{H}{i} line has been extensively observed both in emission and absorption \citep[e.g.,][]{Ewen1951, Muller1951, Heeschen1954, Radhakrishnan1972, Dickey1983, Dickey1990, Gibson2000, Heiles2003a, Li2003, Goldsmith2005}. The atomic gas traced by \ion{H}{i} is widely distributed in the Galaxy \citep[e.g.,][]{Dickey1990, Hartmann1997, Kalberla2009}, and numerous \ion{H}{i} surveys have been carried out \citep[e.g.,][]{Kalberla2005, Stanimirovic2006, stil2006, McClure-Griffiths2009, Peek2011, Dickey2013, Winkel2016, Peek2018} to study the properties of atomic gas and the Galactic spiral structure \citep[e.g.,][]{vandeHulst1954, Oort1958, Kulkarni1982, Nakanishi2003}.

By studying the \ion{H}{i} emission at low spatial resolution, \citet{Oort1958} constructed the first face-on \ion{H}{i} distribution map of the Milky Way, and found multiple spiral arms. Later surveys have revealed additional spiral arms in the outer Galaxy \citep[e.g.,][]{Weaver1970, Kulkarni1982, Nakanishi2003, Levine2006}. While most of these works are concentrated on the outer Galaxy, by combining \ion{H}{i} and H$_2$ map derived from CO observations at low angular resolution, \citet{Nakanishi2016} were able to trace the spiral arms from the inner to the outer Galaxy.

Assuming the 21~cm line is optically thin, the total \ion{H}{i} mass of the Milky Way has been estimated to be 7.2 to 8.0$\times10^9~M_\odot$ \citep{Kalberla2009, Nakanishi2016}. Studies towards nearby gas at high latitudes show that optical depth can be negligible for \ion{H}{i} mass estimation in such a context \citep[e.g.,][]{Lee2015, Murray2018a}, while on the other hand, studies of \ion{H}{i} self absorption towards nearby galaxies (M31, M33 and LMC) revealed that \ion{H}{i} mass can increase by 30--34\% with optical depth correction \citep{Braun2009, Braun2012}. A study toward mini starburst region W43 in our Milky Way revealed an even more extreme correction factor of 240\% for \ion{H}{i} mass estimation when applying optical depth correction. However, no systematic study has yet been done in the Galactic plane.

THOR provides the opportunity to study the distribution and spiral structures of the atomic gas in the northern Galactic plane with the \ion{H}{i} emission data, to further investigate the optical depth, and calibrate the mass estimation of the atomic gas using absorption data.
Furthermore, the atomic hydrogen gas, especially the cold neutral medium (CNM, $T\sim40-100$~K, \citealt{McKee1977, Wolfire1995}) also traces the \ion{H}{i}-to-H$_{2}$ transition. Combining the \ion{H}{i} absorption lines with the simultaneously observed OH absorption lines from the THOR survey and complementary molecular gas information from such as CO observations allows us to study the transition phase between atomic gas and molecular gas \citep{rugel2018}.

This paper presents the second data release of the THOR survey. We focus scientifically on the \ion{H}{i} emission and absorption. The observation strategy and data reduction details are described in Sect.~\ref{sect_obs}. The parameters of the data products, along with an overview of the \ion{H}{i} results are presented in Sect.~\ref{sect_results}. The \ion{H}{i} results are discussed in Sect.~\ref{sect_discuss}, and our conclusions are summarized in Sect.~\ref{sect_con}.

\section{Observations and Data reduction}
\label{sect_obs}
We observed the first quadrant of the Galactic plane, covering $l=14.0-67.4^\circ$ and $\lvert b \rvert \leq 1.25\degr$ with the VLA in C-configuration in L band from 1 to 2~GHz. The observations were carried out in three phases, a pilot study ($l=29.2\degr-31.5\degr$), phase 1 ($l=14.0\degr-29.2\degr,\ 31.5\degr-37.9\degr$ and $47.1\degr-51.2\degr$), and phase 2 ($l=37.0\degr-47.9\degr$ and $51.1\degr-67.4\degr$), spanning across several semesters (from 2012 to 2014). The detailed observing strategy and data reduction are discussed and described in \citet{Bihr2016}, and data release 1 in \citet{beuther2016}, which present only the pilot and phase I data. With the WIDAR correlator, we cover the \ion{H}{i} 21~cm line, four OH lines ($\Lambda$ doubling transitions of the OH ground state, the ${\rm {}^{2}\Pi_{3/2};J=3/2}$ state, ``main lines'' at 1665 and 1667~MHz, ``satellite lines'' at 1612 and 1720~MHz), 19 H$\alpha$ recombination lines, as well as eight continuum bands, for instance, SPWs. Each continuum SPW has a bandwidth of 128~MHz. Due to strong radio frequency interference (RFI) contaminations, two SPWs around 1.2 and 1.6~GHz were not usable and were discarded. The remaining six SPWs are centered at 1.06, 1.31, 1.44, 1.69, 1.82, and 1.95~GHz. For the fields at $l=23.1-24.3^\circ$ and $25.6-26.8^\circ$, the SPW around 1.95~GHz is also severely affected by RFI and is therefore flagged \citep[see][]{Bihr2016}. Each pointing was observed three times to ensure a uniform $uv$-coverage, and the total integration time is $5-6$~min per pointing. A detailed description of the observational setup can be found in \citet{beuther2016}.

The full survey was calibrated and imaged with the Common Astronomy Software Applications (CASA)\footnote{\url{http://casa.nrao.edu}; version 4.1.0 for the pilot study and phase 1, version 4.1.2 for phase 2.} software package \citep{McMullin2007}. The modified VLA scripted pipeline\footnote{\url{https://science.nrao.edu/facilities/vla/data-processing/pipeline/scripted-pipeline}} (version 1.2.0 for the pilot study and phase 1, version 1.3.1 for phase 2) was used for the calibration. The absolute flux and bandpass were calibrated with the quasar 3C~286. J1822-0938 (for observing blocks with $l<39.1\degr$) and J1925+2106 (for the remaining fields) were used for the phase and gain calibration. Except for the RRLs, all data were inverted and cleaned with multiscale CLEAN in CASA to better recover the large scale structure \citep[see also][]{beuther2016}.

In most regions, the individual RRLs are too weak to be detected, and so cleaning the image is typically not useful. We therefore stacked the dirty images of all RRL spectral windows that are not affected by RFI with equal weights in the velocity. All RRL dirty images were produced with the same spectral resolution of 10~km~s$^{-1}$ and smoothed to a common angular resolution of 40\arcsec\ before the stacking \citep[see also ][]{beuther2016}.

For the continuum and RRL data, we employed the RFlag algorithm in CASA, which was first introduced to AIPS by E. Greisen in 2011 to minimize the effects from RFI in each visibility dataset before imaging. Some SPWs, such as the continuum SPW at $1.2$~GHz and $1.6$~GHz, and some RRLs, have so much RFI over the whole band that no usable data could be recovered by RFlag, and were therefore abandoned \citep[see also][]{beuther2016, Wang2018}.

\subsection{New \ion{H}{i} dataset}
For the \ion{H}{i} 21~cm line observations, we combined the THOR C-configuration data with the \ion{H}{i} Very Large Array Galactic Plane Survey (VGPS, \citealt{stil2006}), which consists of VLA D-configuration data combined with single-dish observations from the Green Bank Telescope (GBT), to recover the large-scale structure. The \ion{H}{i} data from the pilot and phase 1 of the survey were published in data release 1 \citep{beuther2016}, in which we combined the THOR C-configuration images directly with the published VGPS data using the task ``feather'' in CASA. This method does recover the large scale structure, but the quality of the images is not ideal. The images are quite pixelized and contain many sidelobe artifacts (see left panel in Fig.~\ref{fig_hi_compare}).

To improve the image quality, we chose a different method to combine the dataset. We first combined the C-configuration data in THOR with the D-configuration of VGPS in the visibility domain. We subtracted the continuum in the visibility datasets with UVCONTSUB in CASA, and used the multiscale CLEAN in CASA\footnote{version 5.1.1} to image the continuum-subtracted C-configuration data together with D-configuration data. The images were afterward combined with the VGPS images (D+GBT) using the task, "feather", in CASA (see also Wang et al. submitted). Since the D-configuration observations of VGPS cover only $l=17.6\degr-67\degr$, the combined \ion{H}{i} data are restricted to $l=17.6\degr-67\degr$, which is slightly smaller than the sky coverage of the C-configuration-only \ion{H}{i} data ($l=14.0-67.4\degr$). Compared to the \ion{H}{i} images from data release 1, the quality of the new images has significantly improved (Fig.~\ref{fig_hi_compare}). More details about the data products are given in Table~\ref{table_product}.

\begin{figure*}
\centering
\includegraphics[angle=0, width=0.8\textwidth]{{figures/HI_old_new_G24_map}.pdf}
\caption{\ion{H}{i} integrated intensity maps (in the velocity range $-100<v_{\rm LSR}<150$~km~s$^{-1}$) for a sample region. The left panel shows the product in the THOR data release 1, which were obtained by direct feathering of the VLA C- and D-configuration observations with the GBT. The right panel shows the product in the THOR data release 2, which were obtained by combining the VLA C- and D-configuration data in the visibility domain and then feathering with the VGPS.}
\label{fig_hi_compare}
\end{figure*}

\section{Results}
\label{sect_results}
We describe the parameters of the data products, and present an overview of the \ion{H}{i} results in this section.

\subsection{Data release 2}
All spectral line data from the pilot and phase 1, as well as all Stokes I continuum data, have been published and are already available to the community \citep{bihr2015, Bihr2016, beuther2016, Beuther2019, Walsh2016, rugel2018, Wang2018}. In this paper, we publish the data from the second half of the survey, including the new \ion{H}{I} dataset for the whole survey, available at our project website\footnote{\url{http://www.mpia.de/thor}} and at the CDS\footnote{\url{https://cds.u-strasbg.fr}}. We summarize the basic parameters of the data products in Table~\ref{table_product}. Because of different requirements for calibrating and imaging the polarization data \citep[see also][]{beuther2016}, the data reduction of these data for the whole survey is still ongoing. The first results of the Faraday rotation study in Galactic longitude range 39\degr\ to 52\degr\ are presented by \citet{Shanahan2019}. More polarization data should be available at a later stage.

The noise of our data is dominated by the residual side lobes. Particularly in regions close to strong emission from the continuum and the masers, the noise can increase significantly. The noise properties of the continuum data and OH masers are studied in detail by \citet{Bihr2016}, \citet{beuther2016}, \citet{Walsh2016}, \citet{Wang2018}, and \citet{Beuther2019}. We list only the typical noise values in Table~\ref{table_product}.

\begin{table*}
\caption{Properties of the data products in the THOR data release 2.}
\centering
\label{table_product}
\begin{tabular}{l c c c c c r }
\hline\hline
    & Rest Freq. & Width            &$\Delta v$          &beam      &  beam        & noise\tablefootmark{a}\\
    &  (MHz)      & (km~s$^{-1}$) & (km~s$^{-1}$)&  native  &  smoothed  & mJy~beam$^{-1}$\\
\hline\vspace{-0.35cm}\\
\ion{H}{I} & 1420.406 & 277.5& 1.5& --& 40\arcsec & 10\tablefootmark{b}\\
\ion{H}{I}+cont. &1420.406 & 300  & 1.5 &13.0\arcsec~to 19.1\arcsec &  25\arcsec & 10\tablefootmark{b}\\
OH1 & 1612.231&195& 1.5&11.6\arcsec~to 18.7\arcsec& 20\arcsec & 10\tablefootmark{b}\\
OH2 & 1665.402&  195 & 1.5&11.1\arcsec~to 18.1\arcsec& 20\arcsec & 10\tablefootmark{b}\\
OH3\tablefootmark{c} & 1667.359&  195 & 1.5&11.0\arcsec~to 13.7\arcsec &20\arcsec & 10\tablefootmark{b}\\
OH4 & 1720.530& 195 & 1.5& 11.0\arcsec~to 17.6\arcsec &20\arcsec & 10\tablefootmark{b}\\
RRL\tablefootmark{d} & -- &210&10& -- &40\arcsec & 3.0\tablefootmark{e}\\
cont1\tablefootmark{e} & 1060 &--&--&14.7\arcsec~to 24.4\arcsec&25\arcsec& 1.0\\
cont2\tablefootmark{e} & 1310 &--&--&12.2\arcsec~to 19.7\arcsec&25\arcsec& 0.3\\
cont3\tablefootmark{e} & 1440 &--&--&11.6\arcsec~to 18.1\arcsec&25\arcsec& 0.3\\
cont4\tablefootmark{e} & 1690 &--&--&9.5\arcsec~to 15.4\arcsec&25\arcsec& 0.3\\
cont5\tablefootmark{e} & 1820 &--&--&9.1\arcsec~to 14.5\arcsec&25\arcsec& 0.3\\
cont6\tablefootmark{e} & 1950 &--&--&8.2\arcsec~to 13.1\arcsec&25\arcsec& 0.7\\
cont3+VGPS &1420& --&--&--&25\arcsec & 6.5\\
\hline
\end{tabular}
\tablefoot{
\tablefoottext{a}{Typical noise of the data with the smoothed beam. Due to residual side lobes, the noise can be higher in areas round strong sources.}
\tablefoottext{b}{Noise of the line data is measured in the line free channels.}
\tablefoottext{c}{The OH line at 1667~MHz is observed for $l=29.2\degr-31.5\degr,\ 37.9\degr-47.9\degr,$ and $51.1\degr-67.0\degr$.}
\tablefoottext{d}{RRL images were produced by smoothing and stacking all available RRL images.}
\tablefoottext{e}{Each continuum band has a bandwidth of 128~MHz.}
}
\end{table*}

\subsection{OH}
\label{oh}
Continuum subtracted images at both the native and the smoothed resolution (20\arcsec) of the four OH lines are provided to the community. The correlator setup was slightly different between the pilot study, phase 1, and phase 2, which mainly affects the sky coverage of OH lines and RRLs and the native spectral resolution of spectral lines (see \citealt{beuther2016} for details). The OH line at 1667~MHz was only observed in the pilot study and phase 2 ($l=29.2\degr-31.5\degr,\ 37.9\degr-47.9\degr$, and $51.1\degr-67.0\degr$, see also, \citealt{rugel2018} and \citealt{Beuther2019}).

Diverse physical processes are traced by OH masers, from expanding shells around evolved star to shocks produced by star-forming jets or SNRs  \citep{Elitzur1992}. \citet{Beuther2019} survey identified 1585 individual maser spots distributed over 807 maser sites in the THOR survey, among which $\sim$50\% of the maser sites are associated with evolved stars, $\sim20$\% are associated with star-forming regions, and $\sim3$\% are potentially associated with SNRs (see \citealt{Beuther2019} for details).

Thermal OH lines are often detected as absorptions towards strong continuum sources, and they can be used to trace molecular clouds where CO is not detected, so called ``CO-dark'' regions \citep[e.g.,][]{Allen2015, Xu2016}. By studying the two main transitions (1665 and 1667~MHz), \citet{rugel2018} detect 59 distinct OH absorption features against 42 continuum background sources, and most of the absorptions occur in molecular clouds associated with Galactic \ion{H}{ii} regions. This is the first unbiased interferometric OH survey towards a significant fraction of the inner Milky Way, and provides a basis for theoretical and future follow-up studies (see \citealt{rugel2018} for details).

\subsection{RRLs}
\label{rrl}
As mentioned in the previous section, to increase the signal-to-noise (S/N), ratio we smoothed and stacked all available recombination line images. The final RRL images have an angular resolution of 40\arcsec\ and a velocity resolution of 10~km~s$^{-1}$. The typical linewidths of RRLs measured toward \ion{H}{ii} regions are around $\sim20-25$~km~s$^ {-1}$\citep{Anderson2011}, so a 10~km~s$^{-1}$ resolution is reasonable to study the kinematics of \ion{H}{ii} regions.

Combining the RRL data from THOR with complementary CO data, \citet{Rugel2019} found shell-like structures in RLL emission toward W49A. The ionized emission and molecular gas emission show correlation towards the shell-like structures. By comparing to one-dimensional feedback models \citep{Rahner2017, Rahner2019}, \citet{Rugel2019} suggest W49A is potentially regulated by feedback-driven and re-collapsing shells (see \citealt{Rugel2019} for details).

Mostly due to sensitivity limitations, interferometric mapping surveys of RRL emission have been rare \citep[e.g.,][]{Urquhart2004}. The stacking method allows us to achieve higher sensitivities than is usually possible when only single lines are observed. THOR provides the community with a new set of RRL maps towards a large sample of \ion{H}{ii} regions, which can be used for sample statistical studies.

\subsection{Continuum}
\label{continuum}
As presented in \citet{Wang2018}, the THOR survey provides the continuum data (both at the native resolution and smoothed to a resolution of 25\arcsec), as well as a continuum source catalog, to the community. To recover the extended structure, we combined the C-configuration 1.4~GHz continuum data from THOR with the 1.4~GHz continuum data from the VGPS survey (D+Effelsberg) using the task, ``feather'' \citep{Wang2018}. The resulting images for the pilot region and phase 1 are very similar to the ones obtained using the VGPS continuum as an input model in the deconvolution of the THOR data. This combined dataset retains the high angular resolution of the THOR observations (25\arcsec), and at the same time, it can recover the large-scale structure. \citet{anderson2017} identified 76 new Galactic SNR candidates in the survey area with this dataset. \citet{anderson2017} further showed that despite the different bandwidths between the VGPS continuum ($\sim1$~MHz) and the THOR continuum ($\sim128$~MHz), the flux retrieved from the combined data is consistent with the literature.

The continuum source catalog contains 10~387 objects that we extracted across our survey area. With the extracted peak intensities of the six usable SPWs between 1 and 2 GHz, we were able to determine a reliable spectral index (spectral index fitted with at least 4 SPWs) for 5657 objects. By cross-matching with different catalogs, we found radio counter parts for 840 \ion{H}{ii} regions, 52 SNRs, 164 planetary nebulae, and 38 pulsars. A large percentage of the remaining sources in the catalog are likely to be extragalactic background sources, based on their spatial and spectral index distributions. A detailed presentation of the continuum catalog can be found in \citet{Bihr2016} and \citet{Wang2018}.

\subsection{\ion{H}{i}}
For the \ion{H}{i} 21~cm line, in addition to the data cubes from C+D+GBT data, we also provide the C-configuration-only \ion{H}{i} datacubes with continuum at both the native resolution and the smoothed beam (25\arcsec), which can be used to measure the \ion{H}{i} optical depth towards bright background continuum sources \citep{Bihr2016}.

A case study of \ion{H}{i} self-absorption towards a giant molecular filament is presented by Wang et al. (submitted). In the following sections, we focus scientifically on \ion{H}{i} emission and absorption.

\subsubsection{\ion{H}{i} emission}
\label{sect_hi}

Figure~\ref{fig_himom0} shows the C+D+single-dish 1.4~GHz continuum map and the \ion{H}{i} integrated intensity map ($v_{\rm LSR}=-113\sim163$~km s$^{-1}$). While the combined \ion{H}{i} emission data illustrates that the atomic gas is confined near the Galactic mid-plane at lower longitudes ($l<42\degr$), at larger longitudes ($l>54\degr$) gas is more evenly distributed in latitudes. The \ion{H}{i} map in Fig.~\ref{fig_himom0} also shows absorption patterns against some strong continuum sources, such as the star-forming complex W43 at $l\sim30.75\degr$, and W49 at $l\sim43\degr$.

Figure~\ref{fig_hi_channel} depicts the channel maps by integrating the \ion{H}{i} emission over 15~km~s$^{-1}$ velocity bins. The neutral gas is clearly seen located at higher latitude in channels at $v_{\rm LSR}<-38$~km~s$^{-1}$. This is likely due to the \ion{H}{i} disk being strongly warped in the outer Milky Way \citep{Burton1986, Diplas1991, Nakanishi2003, Kalberla2009}. Some cloud structures are more prominent in the channel maps, such as the filamentary structures in the channels at $v_{\rm LSR}<-38$~km~s$^{-1}$. While at negative velocities the filamentary structures can been seen clearly, the emission at positive velocities appears less structured. This observational phenomenon is likely due to higher spatial and velocity crowding of structures at positive velocities. The negative velocity channels are tracing the outer Galactic plane, and there is little line of sight confusion, while at positive velocities, due to near-far distance ambiguity, the emission from multiple spiral arms could be at the same velocity and result in structures at different distances bing blended together.

The integrated intensity map (Fig.~\ref{fig_himom0}) also demonstrates that the angular size of the \ion{H}{i} emission along the latitude is smaller at lower longitudes than at larger longitudes. This is due to the fact that the tangent points are further away at lower longitudes. This is also seen in the channel map (Fig.~\ref{fig_hi_channel}) in the positive velocities, in which the tangent points are traced by the left end of the emission in each panel with positive velocities, and the emission structures appear to be smaller at lower longitudes due to them being further away \citep[see also,][]{Merrifield1992}.

\begin{figure*}[htbp]
\centering
\includegraphics[angle=90, height=23.8cm]{{figures/Cont_1400_mosaic_all_ft_vgps-log-1small}.pdf}
\includegraphics[angle=90, height=24cm]{{figures/THOR_HI_mom-0_-113.0_to_163.0km-s-1small}.pdf}
\includegraphics[angle=90, height=23.8cm]{{figures/Cont_1400_mosaic_all_ft_vgps-log-2small}.pdf}
\includegraphics[angle=90, height=24cm]{{figures/THOR_HI_mom-0_-113.0_to_163.0km-s-2small}.pdf}

\caption{THOR+VGPS 1.4~GHz continuum map and \ion{H}{i} integrated intensity map ($-113<v_{\rm{LSR}} <163$\,km\,s$^{-1}$). The continuum map has a beam size of 25\arcsec, and the beam size for the \ion{H}{i} map is 40\arcsec. In all panels, the circles mark the continuum sources that we used to extract the \ion{H}{i} absorption spectra and construct the optical depth map (see Sect.~\ref{sec_tau}). The Galactic sources are marked with white and black circles, and the extragalactic sources are marked with red circles. A few well-known Galactic sources are also labeled in each panel (W43 at $l\sim31$\degr, W44 $l\sim35$\degr, W49 $l\sim43$\degr and W51 $l\sim49$\degr).}
\label{fig_himom0}
\end{figure*}

\begin{figure*}[htbp]
\centering
\includegraphics[angle=90,height=24cm]{{figures/HI_mosaic_channnel_ft_vgps_all_small}.pdf}
\caption{\ion{H}{i} channel maps produced by integrating the \ion{H}{i} emission over indicated velocity ranges. Strong absorption towards W43 ($l\sim31$\degr), W44 ($l\sim35$\degr), W49 ($l\sim43$\degr) and W51 ($l\sim49$\degr) are clearly visible across several velocity channels.}
\label{fig_hi_channel}
\end{figure*}

By averaging the emission in the latitude axis, we constructed the longitude-velocity ($l-v$) diagram of the \ion{H}{i} emission (Fig.~\ref{fig_hi_pv}). The general shape of the $l-v$ diagram agrees with one obtained with the VGPS data \citep{Strasser2007}, but the higher resolutions reveal much finer details, such as the vertical lanes at $l\sim31\degr,\ 43\degr$, and $\sim49\degr$, which are caused by absorption against the background continuum emission from the star-forming regions W43, W49, and W51, respectively (see also Fig.~\ref{fig_himom0}). We also created the $^{13}$CO(1--0) $l-v$ diagram with the same method and plotted it as contours in Fig.~\ref{fig_hi_pv}. The $^{13}$CO(1--0) data is taken from the Exeter FCRAO CO Galactic Plane Survey \citep{Mottram2010}, and Galactic Ring Survey \citep[GRS,][]{Jackson2006}. We re-gridded the Exeter $^{13}$CO data to the same velocity resolution and coverage as the GRS, so there is no $^{13}$CO coverage at velocities where $v_{\rm LSR}<-5$~km~s$^{-1}$. Compared to the $^{13}$CO emission, the \ion{H}{i} emission also traces more extended and diffuse structures.

The \ion{H}{i} emission in general agrees well with the spiral arm models of \citet{Reid2016}, except for the Outer Scutum-Centaurus (OSC) Arm. The OSC Arm is at a large Galactocentric distance and is outside of our survey area at longitudes larger than 40\degr\ due to the warping and flaring of the outer disk \citep{Dame2011, Armentrout2017}. Thus, we can only detect a small portion of the OSC Arm in the inner part of the Galactic plane that our survey covers, as illustrated in Fig.~\ref{fig_hi_pv}.

Another feature in the $l-v$ diagram is a strong self-absorption pattern at $\sim$5~km~s$^{-1}$ following the Aquila Rift (magenta box in Fig.~\ref{fig_hi_pv}). This absorption feature spans almost 20\degr\ in longitude ($\sim$17\degr\ to 36\degr). The $^{13}$CO emission, on the other hand, lies right inside the absorption feature in the $l-v$ diagram. This large-scale absorption feature could be caused by the Riegel-Crutcher cloud, which centers at $v_{\rm LSR}\sim5$~km~s$^{-1}$ and covers the longitude range $l=345\degr$ to 25\degr,\ and the latitude range $b\leq6\degr$ \citep{Riegel1969, Riegel1972, Crutcher1974}.

\begin{figure*}
\centering
\includegraphics[width=\textwidth]{figures/HI_pv_with_spiral_arms_with_co.pdf}
\caption{\ion{H}{i} longitude-velocity ($l-v$) diagram constructed by averaging the emission in the latitude range $\lvert b \rvert \leq 1.25\degr$. The black contours correspond to the $^{13}$CO(1--0) $l-v$ at 3, 8, 18, 28, and 38 times the rms noise of the $l-v$ diagram (rms = 0.1~K, $T_{\rm MB}$). The $^{13}$CO(1--0) data do not cover the velocity range $v_{\rm LSR}<-5$~km~s$^{-1}$. The overlaid curves trace the Sagittarius, Scutum, Norma, Perseus, Outer, and Outer Scutum-Centaurus (OSC) arms, and smaller features (Local Spur, Aquila Spur, and Aquila Rift) taken from \citet{Reid2016}. The near and far sides of the arms are plotted with dashed and solid lines, respectively. The magenta box marks the absorption feature could be caused by the Riegel-Crutcher cloud. The $^{13}$CO(1--0) data are from the Exeter FCRAO CO Galactic Plane Survey \citep{Mottram2010}, and the GRS \citep{Jackson2006}.}
\label{fig_hi_pv}
\end{figure*}

After resampling both the \ion{H}{i} and $^{13}$CO data to the same angular and spectral resolution (pixel size of 22\arcsec, beam size of 46\arcsec, and velocity resolution of 1.5~km~s$^{-1}$), we constructed the $T_{\rm B}$(\ion{H}{i})/$T_{\rm B}$($^{13}$CO) ratio $l-v$ diagram by dividing the \ion{H}{i} $l-v$ diagram by the $^{13}$CO $l-v$ diagram (Fig.~\ref{fig_ratio_pv}). For the $^{13}$CO $l-v$ diagram, a 3$\sigma$ value was used where the emission is below 3$\sigma$ (1$\sigma=0.04$~K in the $^{13}$CO $l-v$ diagram). As expected, Fig.~\ref{fig_ratio_pv} shows that the $T_{\rm B}$(\ion{H}{i})/$T_{\rm B}$($^{13}$CO) ratio is low where there is $^{13}$CO emission (see also, Sect~\ref{sect_hi_ratio}).

After removing the pixels with no \ion{H}{i} emission ($T_{\rm B}$(\ion{H}{i})$<5\sigma$, 1$\sigma$=0.2~K), the histogram of the $T_{\rm B}$(\ion{H}{i})/$T_{\rm B}$($^{13}$CO) ratio $l-v$ diagram in Fig.~\ref{fig_ratio_hist} reveals one strong peak at $\sim100,$ and a secondary peak at $\sim600$. If we assume both \ion{H}{i} and $^{13}$CO emissions are optically thin and uniform excitation temperature, the variations in the $T_{\rm B}$(\ion{H}{i})/$T_{\rm B}$($^{13}$CO) ratio also represent the variations in the atomic to molecular gas column density ratio. Figure~\ref{fig_ratio_hist} indicates that the atomic-to-molecular gas column density ratio can increase by a factor of six from inter-arm regions to spiral arms. Considering that we used 3$\sigma$ value of the $^{13}$CO $l-v$ diagram for regions where there is no $^{13}$CO emission to construct the $T_{\rm B}$(\ion{H}{i})/$T_{\rm B}$($^{13}$CO) ratio $l-v$ diagram, this factor of six is a lower limit (see also Sect~\ref{sect_hi_ratio}).

\begin{figure*}
\centering
\includegraphics[width=\textwidth]{figures/HI_over_CO_pv_with_spiral_arms.pdf}
\caption{The ratio map $l-v$ diagram of \ion{H}{i} over $^{13}$CO ($T_{\rm B}$(\ion{H}{i})/$T_{\rm B}$($^{13}$CO)) averaged over galactic latitude. The $^{13}$CO(1--0) data do not cover the velocity range $v_{\rm LSR}<-5$~km~s$^{-1}$. The overlaid curves trace the Sagittarius, Scutum, Norma, Perseus, Outer, and Outer Scutum-Centaurus (OSC) arms, and smaller features (Local Spur, Aquila Spur, and Aquila Rift) taken from \citet{Reid2016}. The near and far sides of the arms are plotted with dashed and solid lines, respectively.}
\label{fig_ratio_pv}
\end{figure*}

\begin{figure}
\centering
\includegraphics[width=0.5\textwidth]{figures/HI_CO_pv_ratio.pdf}
\caption{Histogram of the $T_{\rm B}$(\ion{H}{i})/$T_{\rm B}$($^{13}$CO) ratio $l-v$ diagram shown in Fig.~\ref{fig_ratio_pv}.}
\label{fig_ratio_hist}
\end{figure}

\subsubsection{\ion{H}{i} optical depth}
\label{sec_tau}
The THOR C-configuration-only \ion{H}{i} data \citep{beuther2016}, which have not been continuum-subtracted, are used to measure the \ion{H}{i} optical depth towards bright background continuum sources. We extracted the \ion{H}{i} spectra towards all continuum sources with an S/N ratio larger than seven from \citet{Wang2018}. Since the synthesized beam of the C-configuration-only \ion{H}{i} data is 25\arcsec, we extracted the average \ion{H}{i} spectrum from a $28\arcsec\times28\arcsec$ ($7\times$7 pixels) area centered on the position of the continuum source to increase the S/N ratio. We used the software STATCONT \citep{Sanchez-Monge2018} to estimate the continuum level $T_{\rm cont}$ and the noise of the spectra. Some example spectra are shown in Fig.~\ref{fig_spectra}. With the absorption spectra, we can estimate the optical depth towards the continuum source following the method described in \citet{bihr2015}:
\begin{equation}
\tau = -{\rm ln}\left(\frac{T_{\rm{on,\ cont}} - T_{\rm off,\ cont}}{T_{\rm{cont}}}\right),
\label{eq_tau}
\end{equation}
where $T_{\rm on,\ cont}$ is the brightness temperature of the absorption feature measured towards the continuum source, and $T_{\rm off,\ cont}$ is the off-continuum-source brightness temperature. Since we use the THOR C-configuration data to calculate $\tau$, the smooth, large-scale structure is mostly filtered out \citep{beuther2016}. Therefore, we can neglect the off emission $T_{\rm off,\ cont,}$ and simplify Eq.~\ref{eq_tau} to:
\begin{equation}
\tau_{\rm{simplified}} = -{\rm ln}\left(\frac{T_{\rm{on,\ cont}}}{T_{\rm{cont}}}\right) .
\label{eq_tau_simplified}
\end{equation}

For channels with a $T_{\rm{on,\ cont}}$ value less than three times the rms, we use the 3$\sigma$ value to get a lower limit on $\tau$. The bottom panels in Fig.~\ref{fig_spectra} show the $\tau$ spectra for the corresponding sources, and the calculated $\tau$ is always saturated in some channels. Compared to the VGPS VLA D-configuration absorption spectra and the $\tau$ spectra derived from them (resolution 60\arcsec, \citealt{Strasser2007}), the THOR C-configuration absorption spectra are much more sensitive and therefore probing higher optical depth (Fig.~\ref{fig_spectra}).

\begin{figure*}
\centering
\includegraphics[width=0.3\textwidth]{{figures/tau_spectra_G17.910+0.372_comp}.pdf}
\includegraphics[width=0.3\textwidth]{{figures/tau_spectra_G48.241-0.968_comp}.pdf}
\includegraphics[width=0.3\textwidth]{{figures/tau_spectra_G62.078+0.609_comp}.pdf}
\caption{\ion{H}{i} absorption and optical depth ($\tau$) spectra of THOR (thick black spectra) and VGPS (thin red spectra). The dashed lines mark the continuum level $T_{\rm cont}$ in the top panels, and the lower limit of $\tau$ in the bottom panels. The shaded bands in the top panels mark the 1$\sigma$ level of the noise.}
 \label{fig_spectra}
\end{figure*}

In this study, since only $T_{\rm{on,\ cont}}<(T_{\rm cont} - 3~\sigma$) is considered to be real absorption, only sources with $T_{\rm cont}>6~\sigma$ can have channels with real absorption and do not reach the lower limit of $\tau$. In total, 228 sources have a $T_{\rm cont}>6~\sigma$ to make the $\tau$ map, among which $\sim$60\% are Galactic sources (Table~\ref{table_tau}). We listed $T_{\rm cont}$, $\sigma$ of $T_{\rm cont}$, the lower limit of $\tau$, and the integrated $\tau$ including the physical nature of the 228 sources in Table~\ref{table_tau}. We then grid the 228 $\tau$ measurements channel by channel for the whole survey using the nearest-neighbor method\footnote{\url {https://docs.scipy.org/doc/scipy/reference/generated/scipy.interpolate.griddata.html}} to create the $\tau$ data-cube. Since the Galactic sources do not trace any absorption from the gas located behind them, we replaced the optical depth values for these channels with the ones from the nearest extragalactic sources. The resulting integrated $\tau$ map is shown in Fig.~\ref{fig_tau_map}.

The highest integrated $\tau$ we measured is at $l\sim43$\degr, at the location of the high-mass star-forming complex W49A. A very high integrated $\tau$ is measured towards the star-forming complex W43 ($l\sim31$\degr). Figure~\ref{fig_tau_map} shows that higher $\tau$ is measured in the inner longitude range, which is reasonable considering more material is packed along the line of sight due to velocity crowding in regions below $l\sim43$\degr. Since the used $\tau$ spectra are all saturated in some channels, this map represents a lower limit of the optical depth in the survey region.

\begin{figure*}
\centering
\includegraphics[width=\textwidth]{{figures/HI_integrated_tau}.pdf}
\caption{\ion{H}{i} integrated optical depth ($\tau$) map across the velocity range ($-128.5<v_{\rm LSR}<$170~km~s$^{-1}$). The aspect ratio of the figure is modified for demonstration purpose.}
 \label{fig_tau_map}
\end{figure*}

\subsubsection{\ion{H}{i} column density and distribution}
\label{sect_hi_dist}
We estimated the column density of atomic hydrogen from the emission line data (C+D+GBT) using \citep[e.g., ][]{wilson2013}:
\begin{equation}
N_{\rm H} = 1.8224\times10^{18}\: \int T_{\rm S}(v) \tau(v)\, dv.
\label{eq_column_density_hi}
\end{equation}

The optical depth corrected spin temperature is $T_{\rm S}(v)=T_{\rm B}(v)/(1-{\rm e}^{-\tau(v)})$, where $T_{\rm B}$ is the brightness temperature of the \ion{H}{i} emission. We used the $\tau$ data-cube (Sect.~\ref{sec_tau}) to correct the spin temperature channel by channel and estimate the column density.

As shown in Fig.~\ref{fig_himom0} and Fig.~\ref{fig_hi_channel}, \ion{H}{i} absorption against strong continuum sources is clearly seen as negative features in the continuum subtracted emission map, such as toward W43 at $l\sim31\degr$. To derive the column density toward strong continuum sources, we determined a mean brightness temperature from a region of radius 10~\arcmin\ around the continuum source to derive $T_{\rm S}$. Then, we extracted C-configuration-only \ion{H}{i}+continuum spectra from these regions pixel-by-pixel to derive the optical depth (see Sect.~\ref{sec_tau}). With the spin temperature and optical depth derived, we can estimate the column density towards continuum sources and add these to the optical depth corrected column density map. Figure~\ref{fig_nh_histo} shows the histograms of the atomic hydrogen column density integrated between --113 to 163~km~s$^{-1}$ of the survey area. The median value of the column density is 1.8$\times10^{22}$~cm$^{-2}$, which is 38\% higher than the value assuming optically thin emission.

\begin{figure}
\centering
\includegraphics[width=0.5\textwidth]{{figures/HI_N_histo}.pdf}
\caption{Histograms of the atomic hydrogen column density integrated between --113 to 163~km~s$^{-1}$. The black (thin) histogram represents the column density derived assuming the emission is optically thin, and the red (thick) histogram represents the column density corrected fro optical depth. The dashed vertical lines mark the median values of the two histograms, respectively. }
 \label{fig_nh_histo}
\end{figure}

To obtain the distribution of atomic gas in the Galactic plane, we estimated the kinematic distance of each channel and each pixel of the \ion{H}{i} emission map with the Kinematic Distance Utilities\footnote{\url{https://github.com/tvwenger/kd}} \citep{Wenger2018}. The ``universal'' rotation curve of \citet{Persic1996} including terms for an exponential disk and a halo, as well as the Galactic parameters from \citet{Reid2014} are used. See Table.~5 in \citet{Reid2014} for detailed parameters.

To solve the kinematic distance ambiguity in the inner Galaxy (inside the solar orbit), we took the following approach. We assume that the average vertical density profile of the atomic gas $n(z)$ in the inner Galaxy can be described by the sum of two Gaussians and an exponential function \citep{Lockman1984, Dickey1990}:
\begin{equation}
\begin{split}
n(z) =  \ & \sum_{i=1}^2 n_i(0)\ {\rm exp}\ \left[-z^2/\left(2h_i^2\right)\right]\\
             &+ n_3(0)\ {\rm exp}\ \left(-|z|/h_3\right),
\end{split}
\label{eq_hi_vertical}
\end{equation}
with $z$ describing the distance from the Galactic mid-plane. The coefficients from \citet{Dickey1990} are listed in Table~\ref{table_hi_vertical}. Since the volume density distribution of the atomic gas in the mid-plane is approximately axisymmetric with respect to the Galactic center \citep{Kalberla2008}, we can assume the volume density is the same at the same Galactocentric distance in the mid-plane. Furthermore, the $v_{\rm LSR}$ distance profiles are symmetric with respect to the tangent point for the degeneracy part \citep[see also,][]{Anderson2009}, so each velocity bin traces the same line-of-sight distance at the near side as at the far side. Thus we assume the column density is also the same at the same Galactocentric distance at the near and far side in the Galactic mid-plane. Due to the kinematic distance ambiguity in the inner Galaxy, the column density we derived for each pixel at each velocity channel is a combined result from both the far and near side. Thus, we can use Eq.~\ref{eq_hi_vertical} to estimate the percentage of the column density contribution from the near and far side for each line-of-sight to solve the kinematic distance ambiguity.

\begin{table}
\caption{Coefficients of Eq.~\ref{eq_hi_vertical} taken from \citet{Dickey1990}.}
\centering
\label{table_hi_vertical}
\begin{tabular}{l c c}
\hline\hline
i & $n_i(0)$ (cm$^{-3}$) &$h_i$ (pc)\\
\hline
 1    & 0.395 &  90\\
 2   & 0.107 &  225\\
 3   & 0.064 &  403\\
\hline
\end{tabular}
\end{table}

With the kinematic distances determined for each channel, we applied a 5$\sigma$ cut and converted the column density cube into a face-on mean surface density map, shown in Fig.~\ref{fig_faceon}. Comparing to the spiral arm model from \citet{Reid2016}, some of the atomic gas follows the spiral arms well, such as the Sagittarius and Perseus arms, but there is also much atomic gas in the inter-arm regions. Along the Sagittarius and Perseus arms, and in the very outer region beyond the Outer Arm in Fig.~\ref{fig_faceon}, the \ion{H}{ii} region distribution agrees with the atomic gas. However, the Outer Arm itself is not associated with much atomic gas in the face-on plot, although there is good agreement between the \ion{H}{I} emission and the Outer Arm in the $l-v$ diagram. This outer component of the atomic gas was also observed by \citet{Oort1958}, \citet{Nakanishi2003}, and \citet{Levine2006}. \citet{Nakanishi2003} found this emission structure agrees spatially with the Outer Arm discovered by \citet{Weaver1970}. The Perseus Arm and Outer Arm in Fig.~\ref{fig_faceon} are found to be distinct structures in the atomic gas distribution with a void of \ion{H}{i} emission and \ion{H}{ii} regions between the arms. The absolute value of the derived surface density represents a mean surface density along the $z$ direction, and is therefore lower than the results of \citet{Nakanishi2003} and \citet{Nakanishi2016}, which derived a surface density integrated along $z$.

\begin{figure}
\centering
\includegraphics[width=0.5\textwidth]{{figures/H_face_on_surface_density_200pc_reid14_with_bar}.pdf}
\caption{Face-on view of \ion{H}{i} surface mass distribution in the survey area overlaid with spiral arms from \citet{Reid2016}, and \ion{H}{ii} regions from \citet{Anderson2014}. The Galactic center is at $\left[0,~0\right]$, and the Sun is at the top-left corner at a Galactocentric distance of 8.34~kpc \citep{Reid2014}. The gray lanes mark the Outer, Perseus, Sagittarius, and Scutum arms with widths from \citet{Reid2014}. The Local Spur, Aquila Spur, and Norm Arm are marked with white lines. The long bar \citep{Hammersley2000, Benjamin2005, Nishiyama2005, Benjamin2008, Cabrera2008} is marked with the shaded half-ellipse. The crosses mark the \ion{H}{ii} regions from \citet{Anderson2014} excluding the ones that fall into the tangent region (marked with two gray curves).}
 \label{fig_faceon}
\end{figure}

We applied different Galactic models and rotation curves for the kinematic distance determination to create the face-on surface density maps shown in Fig.~\ref{app_faceon}. We find that the face-on density map depends only slightly on the assumed model for the kinematic distance. Compared to Fig.~\ref{fig_faceon} (Galactic parameters from \citealt{Reid2014}, rotational curve from \citealt{Persic1996}), the assumption of a uniform rotational curve (Fig.~\ref{app_faceon}, right) only lowers the gas surface density close to the bar region. Similar changes occur when applying the IAU Solar parameters ($R_0=8.5$~kpc, $\Theta_0=220$~km~s$^{-1}$) and the \citet{Brand1993} Galactic rotation model (Fig.~\ref{app_faceon}, left), together with slightly shifting the gas to higher distances.

\subsubsection{Mean spin temperature of the atomic gas}
With the \ion{H}{i} emission, we can obtain the line-of-sight mean spin temperature or the density-weighted harmonic mean spin temperature using \citep{Dickey2000}:
\begin{equation}
\left<T_{\rm S}\right> = \frac{\int T_{\rm B}(v)\ dv} {\int 1-e^{-\tau(v)}\ dv}.
\label{eq_ts}
\end{equation}

As we show in Fig.~\ref{fig_ts}, the mean spin temperatures in the THOR survey area are between 50 and 300~K, with a median value of 143~K. We do not see any correlation between $\left<T_{\rm S}\right>$ and longitudes. Combining survey data from VGPS \citep{stil2006}, CGPS \citep{Taylor2003}, and SGPS \citep{McClure2005}, \citet{Dickey2009} studied the atomic gas in the outer disk of the Milky Way (outside the solar circle). They found the mean spin temperature to be $\sim$250--400~K, and it stays nearly constant with the Galactocentric radius to $\sim$25~kpc. Since the mean spin temperature $\left<T_{\rm S}\right>$ reveals the fraction of CNM in the total atomic gas (see Equation~8 in \citealt{Dickey2009}), the lower $\left<T_{\rm S}\right>$ we obtained indicates we observe a higher fraction of CNM in our survey area. Since \citet{Dickey2009} only considered the outer Milky Way, the differences in the $\left<T_{\rm S}\right>$ may indicate a higher fraction of CNM in the inner Milky Way.

\begin{figure}
\centering
\includegraphics[width=0.5\textwidth]{{figures/HI_Ts_histogram}.pdf}
\caption{Histograms of density-weighted harmonic mean spin temperature between --113 to 163~km~s$^{-1}$. The dashed vertical lines mark the median values of 143~K.}
 \label{fig_ts}
\end{figure}

\section{Discussion}
\label{sect_discuss}
We discuss the results of \ion{H}{i} overview presented in Sect.~\ref{sect_results} in this section.
\subsection{\ion{H}{i} gas mass}
\label{sect_hi_mass}
With the method described in Sect.~\ref{sect_hi_dist}, we estimate the optical depth corrected total \ion{H}{i} mass in our survey area to 4.7$\times10^8~M_\odot$ (using emission above 5$\sigma$). Combining $^{12}$CO(1--0) and $^{13}$CO(1--0) from the GRS and the Exeter FCRAO CO Survey, \citet{Roman-Duval2016} estimated an H$_2$ mass in the inner Galaxy (inside the solar circle) of 5.5$\times10^8~M_\odot$ (GRS: $18\degr\leq l \leq55.7\degr$, |$b\leq1\degr$|; Exeter: $55\degr\leq l \leq100\degr$, $-1.4\leq b\leq1.9\degr$). Within the solar circle, we estimate the total \ion{H}{i} mass to be 2.1$\times10^8~M_\odot$ ($18\degr\leq l \leq67\degr$, |$b|\leq1.25\degr$). Although the GRS+Exeter survey covers a larger area than THOR, the area they covered inside the solar circle is only $\sim4\%$ larger than THOR, so we can still compare these two masses. Therefore, in the inner Galaxy in this longitude range, the molecular component represents about 72\% of the total gas. This fraction also agrees with the molecular fraction of 50-60\% of total gas inside the solar circle estimated by \citet{Koda2016}, \citet{Nakanishi2016}, and \citet{Miville2017}. Considering the total \ion{H}{i} mass we derived is a lower limit, this percentage is likely an upper limit.

If we assume the \ion{H}{i} emission to be optically thin, the total \ion{H}{i} mass within the whole survey area is estimated to be $3.6\times 10^{8}~M_\odot$. Comparing this with our optical-depth corrected estimate of 4.7$\times 10^{8}~M_\odot$, we find that the mass increases by $\sim$31\% percent with the optical depth correction. Considering that all of the $\tau$ spectra saturate in some channels, this $31\%$ is again a lower limit. We define the ratio between the mass after and before the optical depth correction as $R_{\rm \ion{H}{I}}$, so for the whole survey area $R_{\rm \ion{H}{I}}=1.31$. Assuming optically thin emission, the total mass of the \ion{H}{i} gas of the Milky Way within the Galactic radius of 30~kpc was estimated to be 7.2--8$\times10^{9}~M_\odot$ \citep{Kalberla2009, Nakanishi2016}. If we apply $R_{\rm \ion{H}{I}}=1.31$ to the whole Milky Way, the total \ion{H}{i} gas mass would be 9.4--10.5$\times10^{9}~M_\odot$. We discuss the uncertainties of the total \ion{H}{i} mass in Sect.~\ref{sect_mass_err}.

As part of the pilot study of the THOR project, \citet{bihr2015} estimated the mass of the atomic hydrogen gas in the W43 region after applying the correction for optical depth and absorption against the diffuse continuum emission and derived an $R_{\rm \ion{H}{I}}=2.4$, which is higher than what we have derived for the entire survey. Considering W43 has the second largest integrated $\tau$ in the survey, it is reasonable that a larger than average $R_{\rm \ion{H}{I}}$ was measured here. The optical depth map (Fig.~\ref{fig_tau_map}) also shows higher $\tau$ in the inner longitude region ($l\lesssim 44\degr$) than in the outer longitude region.

In contrast to this, \citet{Lee2015} found $R_{\rm \ion{H}{I}}\sim1.1$ by applying the optical depth correction pixel-by-pixel towards the atomic gas around the Perseus molecular cloud. Combining the 21~cm emission maps from the Galactic Arecibo L-band Feed Array Survey \citep[GALFA-HI][]{Peek2011, Peek2018} and absorption spectra from 21-{\it SPONGE} \citep{Murray2015, Murray2018b}, \citet{Murray2018a} found $1.0<R_{\rm \ion{H}{I}}<1.3$ towards high latitude local ISM ($|b|>15\degr$). Considering that we are observing with much higher angular resolution than GALFA, and multiple spiral arms along the line of sight are at the same velocity in the Galactic plane, it is reasonable that the $R_{\rm \ion{H}{I}}$ we derived is higher. On the other hand, studies toward nearby galaxies (M31, M33 and LMC) found $R_{\rm \ion{H}{I}}\sim1.3-1.34$ \citep{Braun2009, Braun2012}, which is in agreement with what we found.

\subsection{\ion{H}{i} gas distribution}
Ever since \citet{vandeHulst1954} and \citet{Oort1958} discovered the spiral structure of the atomic hydrogen gas in the Milky Way, considerable effort has been devoted to investigating the gas distribution and spiral arms in the Galaxy \citep[e.g.,][]{Kulkarni1982, Nakanishi2003, Levine2006, Kalberla2009, Nakanishi2016}. The structure outside of the Outer Arm in Fig.~\ref{fig_faceon} was also observed by \citet{Oort1958}, \citet{Nakanishi2003}, \citet{Levine2006}, and \citet{Nakanishi2016}. \citet{Nakanishi2003} fit this structure with the so-called Outer Arm with a pitch angle of $\sim7\degr$ in the polar coordinates (the x-axis is the azimuthal angle $\theta$ and the y-axis the Galactic radius $R$ in log scale). They found that this agrees with the Outer Arm found by \citet{Weaver1970}. Also, one of the arms fit by \citet{Levine2006} goes through the northern part of this structure (Y~$>0$, X~$>10$ in Fig.~\ref{fig_faceon}). \citet{Levine2006} claimed that the spiral arm model derived from the \ion{H}{ii} regions \citep{Morgan1953, Georgelin1976, Wainscoat1992} could not fit this structure, although Fig.~\ref{fig_faceon} shows that many \ion{H}{ii} regions are associated with this structure. The Outer Arm plotted in Fig.~\ref{fig_faceon} is extrapolated from the pitch angle fitted to parallax sources at greater longitudes \citep[$l>70\degr$,][]{Reid2016}. Since the pitch angle can vary by azimuth angle \citep{Honig2015}, the real Outer Arm in this region ($17\degr<l<67\degr$) could have a different pitch angle and be at a larger Galactocentric radius. On the other hand, the noncircular motions in the outer \ion{H}{i} disk \citep[e.g.,][]{Kuijken1994} could also affect the \ion{H}{i} distribution we derived in this region.

Another feature in the inner part of Fig.~\ref{fig_faceon} is that the region right below the end of the bar shows low surface density. Depending on the Galactic rotation model we used to determine the kinematic distances, there could even be a cavity in this region (all emission is below 5$\sigma$ and masked out, Fig.~\ref{app_faceon}). The region is located where the Galactic long bar ends \citep{Hammersley2000, Benjamin2005, Nishiyama2005, Benjamin2008, Cabrera2008}. The long bar introduces strong non-circular motions in the sources, and so the axisymmetric rotation curve does not apply on and near the bar \citep{Fux1999, Rodriguez2008, Reid2014}. Thus, the kinematic distances derived for the gas and most \ion{H}{ii} regions in this region may have large errors. Therefore, the low-level emission may not be real. The same low-level distribution is also seen in the CO map by \citet{Roman-Duval2009, Roman-Duval2016}, \ion{in H}{ii} regions. Considering all these distributions are based on kinematic distance (except for the distance of less than 10\% \ion{H}{ii} regions in this region are derived from parallax), we should consider the distribution of gas and \ion{H}{ii} regions inside Scutum Arm with caution.

\subsection{Atomic to molecular gas ratio}
\label{sect_hi_ratio}
Our optical depth correction discussed in the previous sections involves a lot of interpolation and averaging. We would like to avoid doing it when comparing the \ion{H}{i} and $^{13}$CO maps, since interpolation and averaging brings large uncertainties to each particular region. In the following discussion, we compare the \ion{H}{i} and $^{13}$CO emission directly.

As we demonstrate in Fig.~\ref{fig_faceon}, high column density gas is concentrated along and above the Sagittarius Arm in the inner Galaxy. This is also seen by \citet{Nakanishi2016}. On the other hand, molecular clouds traced by CO are mainly distributed around and inside the Scutum Arm \citep{Roman-Duval2009, Nakanishi2016}. The molecular cloud fraction ($f_{\rm mol}$) map in \citet{Nakanishi2016} shows that $f_{\rm mol}$ is anti-correlated with Galactocentric distance. Compared to Fig.~\ref{fig_faceon}, inside the Sagittarius Arm, the molecular cloud fraction may be as high as $f_{\rm mol}>0.6$, while in the outer regions, $f_{\rm mol}$ quickly drops to almost zero \citep[see also, ][]{Miville2017}. However, they did not discuss how this ratio varies between inter-arm regions and spiral arm regions.

As the $l-v$ diagrams in Fig.~\ref{fig_hi_pv} and Fig.~\ref{fig_ratio_pv} show that the majority of the molecular gas is tightly associated with the spiral arms, while the atomic gas on the other hand is more widely distributed with significant material in the inter-arm regions. The histogram of $T_{\rm B}$(\ion{H}{i})/$T_{\rm B}$($^{13}$CO) ratio shows a bimodal distribution (Fig.~\ref{fig_ratio_hist}). If we assume both $^{13}$CO and \ion{H}{i} emissions are optically thin, the $T_{\rm B}$(\ion{H}{i})/$T_{\rm B}$($^{13}$CO) ratio bimodal distribution could be proxy of the atomic-to-molecular gas ratio. Therefore, we can interpret from Fig.~\ref{fig_ratio_hist} that on average, the atomic-to-molecular gas ratio may increase by approximately a factor of six from spiral arms to inter-arm regions.

\subsection{Uncertainties of the \ion{H}{I} optical depth $\tau$}
The uncertainties of the \ion{H}{i} optical depth are determined mainly by two factors, the brightness of the continuum source and the rms noise of the absorption spectra. The ratio of these two is the S/N ratio. As we mentioned in Sect.~\ref{sec_tau}, we selected sources with an S/N ratio $>$6 to ensure that the spectra have real absorption and the $\tau$ spectra is not saturated in all channels. Thus, the S/N ratio for the selected spectra ranges between six and 250, with a median value of 12, and the uncertainties associated with the rms noise are between 0.18 to 0.004 with a median value of 0.09, depending on the brightness of the continuum source.

Another source of uncertainty for the optical depth $\tau$ is that the $\tau$ spectra are all saturated in some channels, as shown in Fig.~\ref{fig_spectra}. To test the $\tau$ limits, high sensitivity VLA follow-up observations were carried out towards three selected sources, G21.347--0.629, G29.956--0.018, and G31.388--0.384 (Rugel et al., in prep.). In the THOR survey, where each field was observed for five to six~minutes in on-source time, the optical depths of these three sources all saturate at $\tau\sim$2.7 to 3.1. In the follow-up observations, each continuum source was observed for significantly longer, and the noise dropped by $\sim50-70\%$. However, many channels in the $\tau$ spectra still saturate at $\tau\sim3.5-3.9$ if we smooth the data to the same angular and spectral resolution as the THOR C-configuration data. Depending on the S/N ratio of the continuum source, this $\sim50-70\%$ drop in the noise could increase the lower limit of the optical depth to $\sim1.2-2.6$ times the current value, and also increase the optical-depth corrected column density to $\sim 1.1-1.6$ times the current value (Fig.~\ref{fig_ratio}).

\begin{figure}
\centering
\includegraphics[width=0.45\textwidth]{{figures/tau_snr_factor}.pdf}
\caption{Increase of the optical depth lower limit (top panel) and the column density (bottom panel) if the noise drops by 50\% (dashed line) and 70\% (solid line) plotted as a function of S/N ratio. The shaded histogram in each panel is the S/N ratio distribution of the continuum sources we used to extract the \ion{H}{i} absorption spectra and construct the optical depth map. }
 \label{fig_ratio}
\end{figure}

\subsection{Uncertainties of the \ion{H}{I} mass}
\label{sect_mass_err}
The uncertainties of the mass estimation for atomic gas originate from several factors: the optical depth, the distance, absorption against the diffuse continuum emission, and the \ion{H}{i} self absorption (HISA). As we discussed in the previous section, we could be underestimating the peak optical depth $\tau_{\rm limit}$ by 20 to 160\%, but the impact on the integrated optical depth is not clear. If we assume the noise levels of the $\tau$ spectra drop to 30\% of the values listed in Table.~\ref{table_tau}, with the same 228 sources to correct the optical depth, the total \ion{H}{I} mass increases by 9\%. However, as we mentioned in the previous section, many channels in the $\tau$ spectra still saturate in the high sensitivity follow-up observations, and this 20\% is still a lower limit.

The second main factor of uncertainty is the distance. With different Galactic parameters, we get different kinematic distances, which result in different mass estimates. With the rotation curve of \citet{Persic1996}, and the Galactic parameters from \citet{Reid2014}, we derived the total mass 4.7$\times10^8 M_\odot$. With the same Galactic parameters from \citet{Reid2014} but assuming a uniform rotational curve, we would get the same mass. If we take the IAU Solar parameters ($R_0=8.5$~kpc, $\Theta_0=220$~km~s$^{-1}$) and Galactic rotation model from \citet{Brand1993}, the total mass increases by 13\%. We are also aware that assuming axisymmetry and using the average vertical density distribution $n(z)$ of \ion{H}{i} to solve the kinematic distance ambiguity of the column density distribution is not ideal, but this is the best we can do without detailed modeling of the Galactic disk. Furthermore, \citet{Wenger2018} compared the kinematic distances with the parallax distances of 75 Galactic high-mass star-forming regions, and they found out that the kinematic distances we used in this paper (derived with the rotation curve of \citet{Persic1996} and the Galactic parameters from \citet{Reid2014}) have a median offset of 0.43~kpc, with a standard deviation of 1.24~kpc from parallax distances.

\citet{bihr2015} estimated the mass of the atomic hydrogen gas in W43 to be $6.6_{-1.8}\times10^6~M_\odot$ after applying the correction for optical depth and absorption against the diffuse continuum emission ($l=29.0-31.5\degr,\ |b|\leq 1\degr,\ v_{\rm LSR}=60-120$~km~s$^{-1}$). By integrating across the same velocity range, we derived a mass of 8.5$\times10^6~M_\odot$ within the same area with our distance determination method. The mean distance at $l=30.25\degr$ between 60 to 120~km~s$^{-1}$ from our method is 7.4~kpc, much larger than the distance of 5.5~kpc \citep{Zhang2014} adopted by \citet{bihr2015}. Taking the same distance 5.5~kpc results in a mass of $4.9\times10^6~M_\odot$. Further applying correction for the absorption against the diffuse continuum emission with the method described in \citet{bihr2015} increases the mass by 19\% to $5.7\times10^6~M_\odot$, which approximately agrees with what \citet{bihr2015} estimated, but is slightly smaller. Since \citet{bihr2015} use one single strong continuum source to correct the optical depth for the whole W43 region, they may overcorrect for the outer region in W43. The 19\% mass increase from applying a correction for the absorption against the diffuse continuum emission is an upper limit if we consider the whole survey area, since W43 is one of the most extreme star-forming complexes in the Milky Way and is considered to be a mini starburst region \citep{Nguyen2011, Beuther2012, Nguyen2013, Zhang2014}. Furthermore, to correct the diffuse continuum emission, we need information on its distance. It is reasonable to assume all diffuse continuum emission is in the background and correct it for a particular region, but we can not apply this to the whole survey. Thus, we do not apply any correction for the diffuse continuum emission.

The last factor is HISA, which we did not consider for the mass estimation. However, HISA was studied towards a Giant Molecular Filament (GMF) with the THOR data by Wang et al., submitted, and they showed, for this specific GMF, that the mass traced by HISA is only 2-4\% of the total \ion{H}{i} mass. Studies of \ion{H}{i} narrow self absorption (HINSA) show that the ratio between the column density traced by HINSA to the H$_2$ column density is $\sim 10^{-3}$ to $2\times 10^{-2}$ \citep{Li2003, Goldsmith2005, Zuo2018}. As we discussed in Sect.~\ref{sect_hi_mass}, the total H$_2$ mass in this part of the Galactic plane is also comparable to the \ion{H}{i} mass, the effect of HISA and HINSA to the \ion{H}{i} mass is negligible. In summary, we could still be underestimating the \ion{H}{i} mass by 20 to 40\%, even with the current optical depth correction.

\section{Conclusions}
\label{sect_con}
In this paper, we describe the THOR data release 2, which includes all OH and RRL data, and an entire new \ion{H}{i} dataset from the THOR survey. In addition, a detailed analysis of the \ion{H}{i} data is presented. The main results can be summarized as follows:
\begin{enumerate}
\item While the \ion{H}{i} channel map shows clear filamentary substructures at negative velocities, the emission at positive velocities is more smeared-out. This is likely due to higher spatial and velocity crowding of structures at positive velocities. Both the $l-v$ diagram and the face-on view of the \ion{H}{i} emission show that some of the atomic gas follows the spiral arms well, such as the Sagittarius and Perseus Arm, but there is also much gas in the inter-arm regions.
\item We produced a spectrally resolved \ion{H}{i} $\tau$ map from 228 absorption spectra.
\item We corrected optical depth for the \ion{H}{i} emission with the $\tau$ map. The atomic gas column density we derived with optical depth correction is 38\% higher than the column density derived with optically thin assumption. We estimate the total \ion{H}{i} mass in the survey region to be 4.7$\times10^8~M_\odot$, 31\% higher than the mass derived with the optically thin assumption. If we apply this 31\% correction to the whole Milky Way, the total atomic gas mass would be 9.4--10.5$\times 10^9~M_\odot$.
\item Considering that all the $\tau$ spectra are saturated in some channels and we did not apply the correction for the diffuse continuum emission, we could be underestimating the mass by an additional 20--40\%. Future higher sensitivity observations are needed to better constrain the optical depth.
\item We constructed a face-on view of the mean surface density of the atomic gas in the survey area.
\item We estimated the density-weighted harmonic mean spin temperature $\left<T_{\rm S}\right>$ integrated between --113 and 165~km~s$^{-1}$ with a median value of $\left<T_{\rm S}\right>\sim143$~K, about a factor of two lower than what was estimated in the outer disk of the Milky Way, which may indicate a higher fraction of CNM in the inner Milky Way.
\item The latitude averaged $T_{\rm B}$(\ion{H}{i})/$T_{\rm B}$($^{13}$CO) ratio distribution shows two peaks at $\sim$100 and $\sim$600, which may indicate that the atomic-to-molecular gas ratio can increase by a factor of six from spiral arms to inter-arm regions.
\end{enumerate}

The \ion{H}{i}, OH, RRL, and continuum data from the THOR survey together provide the community the basis for high-angular-resolution studies of the ISM in different phases.

\begin{acknowledgements}
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. Y.W., H.B., S.B., and J.D.S. acknowledge support from the European Research Council under the Horizon 2020 Framework Program via the ERC Consolidator Grant CSF-648505. H.B., S.C.O.G., and R.S.K. acknowledge support from the Deutsche Forschungsgemeinschaft in the Collaborative Research Center (SFB 881) ``The Milky Way System'' (subproject B1, B2, B8). This work was carried out in part at the Jet Propulsion Laboratory which is operated for NASA by the California Institute of Technology. R.J.S. acknowledges an STFC Rutherford fellowship (grant ST/N00485X/1). N.R. acknowledges support from the Max Planck Society through the Max Planck India Partner Group grant. F.B. acknowledges funding from the European Union's Horizon 2020 research and innovation program (grant agreement No 726384). This research made use of Astropy and affiliated packages, a community-developed core Python package for Astronomy \citep{astropy2018}, Python package {\it SciPy}\footnote{\url{https://www.scipy.org/}}, APLpy, an open-source plotting package for Python \citep{robitaille2012}, and software TOPCAT \citep{taylor2005}.

\end{acknowledgements}

\bibliographystyle{aa}

redpajama_set_name: RedPajamaArXiv


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FILE - In this Dec. 12, 2006, file photo, made available by NASA, astronaut Robert L. Curbeam Jr., left, and European Space Agency astronaut Christer Fuglesang, participate in a space walk during construction of the International Space Station. Under President Donald Trump's 2019 proposed budget released, Monday, Feb. 12, 2018, U.S. government funding for the space station would cease by 2025. The government would set aside $150 million to encourage commercial development. (NASA via AP, File)
Trump aims for moon, pulls back on space station, telescopes
CAPE CANAVERAL, Fla. (AP) — The Trump administration wants NASA out of the International Space Station by 2025, and private businesses running the place instead. Under President Donald Trump's 2019 proposed budget released Monday, U.S. government funding for the space station would end by 2025. The...
A Falcon 9 SpaceX heavy rocket lifts off from pad 39A at the Kennedy Space Center in Cape Canaveral, Fla., Tuesday, Feb. 6, 2018. The Falcon Heavy, has three first-stage boosters, strapped together with 27 engines in all. (AP Photo/John Raoux)
The Latest: SpaceX launches big new rocket; lands 2 boosters
CAPE CANAVERAL, Fla. (AP) — The Latest on SpaceX rocket launch (all times local): 8 p.m. SpaceX chief Elon Musk says the center booster of the Falcon Heavy slammed into the Atlantic at 300 mph, missing the floating landing platform. Musk says it hit the water with such force that shrapnel flew onto...
SpaceX launches new megarocket with Tesla car on board
CAPE CANAVERAL, Fla. (AP) — SpaceX's new megarocket launched on its first test flight Tuesday from Florida's Kennedy Space Center as thousands jammed surrounding beaches. Some details about the Falcon Heavy rocket, its cargo and what's ahead: THE ROCKET The Falcon Heavy has three first-stage...
A super blue blood moon is seen over Los Angeles on Wednesday Jan. 31, 2018. The moon is putting on a rare cosmic show. It's the first time in 35 years a blue moon has synced up with a supermoon and a total lunar eclipse. NASA is calling it a lunar trifecta: the first super blue blood moon since 1982. That combination won't happen again until 2037. (AP Photo/Richard Vogel)
Lunar showstopper: Super blue blood moon awes and wows
CAPE CANAVERAL, Fla. (AP) — The moon put on a rare cosmic show Wednesday: a red blue moon, super big and super bright. It's the first time in 35 years a blue moon has synced up with a supermoon and a total lunar eclipse, or blood moon because of its red hue. Hawaii and Alaska had the best seats,...
FILE - In this Aug. 28, 2007, file photo, the moon takes on different orange tones during a lunar eclipse seen from Mexico City. During a lunar eclipse, the moon's disk can take on a colorful appearance from bright orange to blood red to dark brown and, rarely, very dark gray. On Wednesday, Jan. 31, 2018, a super moon, blue moon and a lunar eclipse will coincide for first time since 1982 and will not occur again until 2037. (AP Photo/Marco Ugarte, File)
Blue moon, supermoon, total lunar eclipse rolled into one
CAPE CANAVERAL, Fla. (AP) — The moon is providing a rare triple treat this week. On Wednesday, much of the world will get to see not only a blue moon and a supermoon, but also a total lunar eclipse, all rolled into one. There hasn't been a triple lineup like this since 1982 and the next won't occur...


Children usually avoid to eat green leafy vegetables so this is my try to provide them nourishing as well as tasty snack.
1. Clean the fenugreek leaves. Wash and chopped the leaves.
2. Soak the Moong Daal in water for a couple of hours.
3. Add them to a blender, blend it for 2-3 min. to make a batter.
4. Add chopped fenugreek leaves, chopped chillies, turmeric powder, jeera and salt.
5. Roughly mash the boiled potatoes and mix in the batter.
6. Check the salt and seasoning.
7. Heat oil in a kadahi/deep bottom pan.
8. To check its sufficient hot, drop a small portion of batter in the oil, if it sizzels and comes to the surface, oil is ready, simmer the fire.
9. Drop small portions of the batter in the oil by a spoon or with your hands.
11. Serve hot with tomato ketchup.


text:
ORP Pilica (896) – polski okręt desantowy projektu 770D (w kodzie NATO: Polnocny-A), pełniący służbę w siłach 8 Flotylli Obrony Wybrzeża w latach 1965-1991.

Budowa
ORP "Pilica" zwodowano w październiku 1964 roku. W kwietniu w czasie procesu przeformowania Flotylli, Zarządzeniem Szefa Sztabu Generalnego WP nr 022/Org z dnia 2 kwietnia 1965 roku, wcielono wybudowany w Stoczni Północnej w Gdańsku okręt desantowy proj. 770D –  ORP "Pilica" (burtowy numer taktyczny 896). Uroczyste podniesienie bandery na ORP "Pilica" nastąpiło 11 kwietnia 1965 roku, otrzymując numer burtowy "896". Wszedł on w skład 2 Brygady Okrętów Desantowych należącej do 8 Flotylli Obrony Wybrzeża, stacjonującej w Świnoujściu. Pierwszym dowódcą ORP "Pilica" był ppor. mar. Bogdan Fabiańczyk. Po 26 latach służby, w styczniu 1991 roku okręt skreślony ze stanu Marynarki Wojennej i sprzedany na złom.

Opis
Okręt przeznaczony był do transportowania morzem ciężkiego i lekkiego sprzętu bojowego. ORP "Pilica" mogła przewozić 5 czołgów podstawowych T-54, przybijając do brzegu oraz mogła prowadzić wyładunek pojazdów amfibijnych (czołgów pływających PT-76, transporterów opancerzonych TOPAS lub transporterów pływających K-61 lub PTS-M) w wodzie w pobliżu brzegu..

Przypisy

Polskie okręty desantowe z okresu po 1945
Okręty zbudowane w Stoczni Północnej w Gdańsku