You will be presented with the full text of a science research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
m31 is an ideal galaxy to study a globular cluster system in a spiral galaxy .
there have been several surveys of globular clusters ( gcs ) in a large region of m31 , but they were all based on photographic plates . there were a few surveys of globular clusters based on ccd observations as well , but they were limited to small areas ( see battistini et al .
1993 , mochejska et al .
1998 , barmby et al . 2000 and references therein ) .
there are currently @xmath2 proposed gc candidates in m31 in the literature . over 200 of these objects
have been confirmed as gcs , 200 have been shown not to be clusters , and the nature of the remaining objects is as yet unknown ( barmby et al . 2000 ) .
therefore , over the past few years , we have undertaken a wide field ccd survey of the globular clusters in m31 .
using the kpno 0.9 m and the tek 2k ccd imager , we have obtained washington @xmath1 images of 53 ( @xmath3 ) fields covering a region @xmath4 deg@xmath5 centered on m31 to search for new gc candidates .
figure 1 illustrates a finding chart of m31 showing our survey region . then using the wiyn 3.5 m and hydra ( multi - fiber spectrograph ) we have obtained spectra covering 38007000 of about 500 gc candidates . we have obtained
the photometry of the point sources and the extended sources in the images using doaphot ii / allframe , and have reduced the hydra spectra using the iraf / dohydra .
we have selected globular cluster candidates using several criteria : a ) color - magnitude diagrams , b ) color - color diagrams , c ) morphological classifiers based on the radial moments and the difference between the aperture magnitude and the point spread function fitting magnitude , and d ) visual inspection of the images .
our recovery rate of the known bonafide gcs is estimated to be @xmath6 .
finally we have used the spectra for confirming the gc candidates ( see seguel et al .
2001 as well ) .
our new photometric survey has produced a total of @xmath7 new gc candidates with @xmath8 ( @xmath9 ) mag .
about 600 among these candidates are classified as class 1 ( probable gc candidates ) and class 2 ( possible gc candidates ) , approximately doubling the number of good gc candidates .
figure 2 shows a color - magnitude diagram of sample new gc candidates as well as the known gcs , background galaxies and stars in one selected field ( see kim et al .
2001 for details ) .
note how successfully the known gcs are recovered and how many more new gc candidates ( especially faint ones ) are found in our new survey .
figure 3 displays @xmath10 luminosity function and @xmath11 color distribution of the new gc candidates .
luminosity function continues to increase with increasing magnitude , passing the expected turnover at @xmath12 mag .
this shows that the faint end in the luminosity function ( @xmath13 mag ) contains many non - globular cluster objects .
color distribution of the gc candidates with @xmath14 mag shows a hint of bimodality , but needs a further study to confirm it .
finally aperture photometry of the gc candidates will be used for further analysis .
however , these new gc candidates discovered as part of our photometric survey need to be confirmed by spectroscopy .
as for the current spectroscopic data of the m31 gcs , barmby et al .
( 2000 ) contains so far the most comprehensive catalog , which still only contains 200 velocity measurements and 188 spectroscopic metallicities of the gc candidates previously known .
spectroscopic data are being analyzed now .
figure 4 displays sample spectra of new gcs with @xmath15 mag spectroscopically confirmed .
several features typical for globular clusters ( ca ii h and k , h@xmath16 , g band , mgb complex , fe 5270 , na d , and h@xmath17 lines ) are clearly noticed in the spectra .
it is pleasing to find not only new gcs as faint as 19.0 mag but also new gcs as bright as 14.9 mag in our survey .
we are planning to confirm spectroscopically most of the new gc candidates in m31 .
when our survey is finished , a new m31 gc catalog will be made , combining the new gcs and the known gcs .
the final catalog of m31 globular clusters will be used : 1 ) to derive a reliable gc luminosity function for m31 , the faint end of which was very incomplete in the previous data ; 2 ) to investigate the bimodality of the metallicity distribution , which was seen only in the spectroscopic data of the previous catalog , but not clearly in any photometric data ( barmby et al . 2000 ) ; 3 ) to investigate the difference in mean luminosity between the metal - poor gcs and the metal - rich gcs .
the present catalog of m31 globular clusters shows that the metal - poor gcs are 0.4 mag fainter than the metal - rich gcs ( barmby et al .
2000 , barmby 2001 ) , which is the opposite to the case of the gcs in early - type galaxies and our galaxy ( larsen et al .
our new catalog will be helpful to resolve this discrepancy ; and 4 ) to investigate the systematic difference in kinematics between the metal - poor and the metal - rich gcs , which provides critical information on the age difference between the two populations and strong constraints on galaxy formation scenarios .
barmby , p. , huchra , j. p. , brodie , j. p. , forbes , d. a. , schroder , l. l. , & grillmair , c. j. 2000 , , 119 , 727 barmby , p. 2001 , this volume battistini , p. l. , bonoli , f. , casavecchi , m. , ciotti , l. , federici , l. , & fusi pecci , f. 1993 , , 272 , 77 kim , s. c. , lee , m. g. , geisler , d. , seguel , j. , sarajedini , a. , & harris , w. e. 2001 , this volume .
larsen , s. et al .
2001 , this volume mochejska , b. j. , kaluzny , j , krockenberger , m. , sasselov , d. d. , & stanek , k. z. 1998 , acta astron . , 48 , 455 seguel , j. , geisler , d. , kim , s. c. , lee , m. g. , sarajedini , a. , & harris , w. e. 2001 , this volume
we present a progress report of our wide field ccd survey of globular clusters in m31 . 
 we have covered 3 deg @xmath0 3 deg area centered on m31 , using the kpno 0.9 m and washington @xmath1 filters . 
 our survey is much deeper and more sensitive than previous surveys . 
 we have found several hundred new globular cluster candidates in m31 in addition to confirming previously known globular clusters , and also have found a number of interlopers among previous globular cluster catalogs . 
 we have also obtained spectra of about 500 objects among these candidates using the hydra at the wiyn 3.5 m telescope , which are used for classification and measuring the radial velocity of the candidate objects . when completed , 
 a new master catalog of globular clusters in m31 will be made , combining the new globular clusters with the known globular clusters .    
 # 1_#1 _ # 1_#1 _ =    # 1 1.25 in .125 in .25 in