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molecular spectral line observations are a powerful tool for obtaining information about kinematics , temperature and density in star forming clouds .
the combination of the observations of several molecules can be used to give a complete information of the environment of protostars and the stage of their evolution .
ccs molecular lines are very useful for making studies related to the structure and the physical conditions of the clouds , since they are not very opaque but they are intense and abundant in these regions , and its lack of hyperfine structure makes ccs a good molecule for dynamical studies ( saito et al .
1987 , suzuki et al .
ccs is a high density tracer , like nh@xmath5 .
the spatial distribution of these two molecules can be used as a clock to date the age of the clouds , since a spatial anticorrelation between these two molecules has been observed in dark clouds , and has been interpreted in terms of chemical evolution ( velusamy et al .
1995 , kuiper et al .
1996 ) .
mass - loss phenomena are common in the earliest stages of stellar evolution .
this activity can be traced by water maser emission ( rodrguez et al .
moreover these masers provide a good characterization of the age of low - mass young stellar objects ( ysos ) , since class 0 sources are the most probable candidates to harbor this emission ( furuya et al .
2001 ) .    in order to diagnose the physical conditions around ysos , and study the dynamics and the stage of evolution , we have analyzed the properties of ccs , nh@xmath5 , and water masers in the cloud surrounding the far - infrared source b1-irs ( iras 03301 + 3057 ) , a class 0 source ( hirano et al .
1997 ) located in the b1 molecular cloud .
simultaneous observations of the j@xmath6=2@xmath7 - 1@xmath8 transition of ccs ( rest frequency = 22345.388 mhz ) and the 6@xmath9 - 5@xmath10 transition of h@xmath11o ( rest frequency = 22235.080 mhz ) were carried out on 2003 april 4 using the very large array ( vla ) of the national radio astronomy observatory ( usa ) in its d configuration .    we have also processed vla archive data of the nh@xmath5(1,1 ) transition ( rest frequency = 23694.496 mhz ) . the observations were made on 1988 august 13 , with the d configuration .
in addition to all these radio data , we have retrieved a k - band image from the image data of the two micron all sky survey ( 2mass ) , to get a better position for the infrared source .
this image was processed with aips , and convolved with a gaussian of 5@xmath1 fwhm , to search for extended emission .
the most interesting characteristics of the ccs emission are its clumpy spatial distribution and the observed velocity gradient
. there are three main clumps surrounding the central source , all of them are redshifted with respect to the systemic velocity of the b1 core ( @xmath12 = 6.3 km s@xmath13 , hirano et al .
the molecular gas in all these clumps shows clear velocity gradients , with less redshifted velocities at positions closer to the central object ( see fig .
the ammonia emission is very extended ( @xmath14 ) and clumpy .
the general tendency observed consists in a spatial anticorrelation with respect to the ccs emission , never reported before at such small scales ( @xmath04@xmath1 , 1400 au at 350 pc ) .
we think that this anticorrelation is related to the chemical evolution of the source , but we need to continue with this kind of studies in other sources similar to b1-irs to derive consistent conclusions about the meaning of this distribution .
our water maser observation shows a cluster of 23 spots , most of them are redshifted with respect to the main cloud velocity .
they form an elongated structure ( see fig 2 ) , with a length of @xmath0 1.@xmath13 ( 455 au at 350 pc ) .
we have detected a point - like source at 2 @xmath4 m from the 2mass archive .
convolving the k - band image with a gaussian of 5@xmath1 fwhm , we have noticed an extended emission elongated south west from the point source .
the point - like source detected at 2 @xmath4 m is located inside the error box of the iras source ( see fig 3 ) , at a distance of @xmath15 6@xmath1 from the iras catalog position and at @xmath161@xmath1 ( 350 au ) from the water masers . due to their proximity
, it is very probable that this 2 @xmath4 m source is the exciting source of the maser emission and of the molecular outflow .
the extended ir emission detected in the k - band is a reflection nebula elongated in the same direction as the water masers .
our dynamical calculations reveal that motions of the water masers are unbound , since a mass of @xmath1712 m@xmath18 within 175 au would be needed to bind them .
such a high mass is not consistent with our nh@xmath5 and ccs data .
due to their proximity to the exciting source , and the shape and size of the distribution of the masers , it is very likely that the maser emission delineates the inner ( 1@xmath1 ) part of the jet that is driving the co outflow , near b1-irs and detected by @xcite .
the velocity pattern observed in the ( redshifted ) ccs clumps can be interpreted in terms of infalling clumps which are strongly interacting with the outflow .
what we see could be foreground ccs clumps falling toward the central source , but being stopped by the wind , explaining in this way the less redshifted velocities observed in the ccs lines at positions closer to the central source ( fig .
however , an alternative possibility is that we could be observing the ccs clumps in the background moving away from the source and being accelerated by the molecular outflow .
the moderately - high velocity blueshifted co emission detected by @xcite was proposed to be in a near pole - on configuration due to the position of the iras source with respect to the outflow , which was located just at the center of the blueshifted emission ( fig .
3 ) .      first ,
the 2 @xmath4 m point - like source , which is probably powering the outflow ( as suggested by its association with the water masers ) , is not located at the center but at the tip of the blueshifted co emission .
the extended 2 @xmath4 m emission is elongated in the same direction that the cluster of water masers , and it is coincident with the shape of the co outflow .
this coincidence further reinforces that the 2 @xmath4 m source marks the position of the powering source , and that the blueshifted lobe of the outflow is oriented towards the southwest of it .
moreover the velocity gradient of the ccs can not be explained by a pole - on outflow .
an outflow in the plane of the sky , however , could sweep the ccs material providing the velocity gradient observed .
the geometry on the plane of the sky is reinforced by the lack of a velocity gradient of the water masers along its jet - like structure .
ga , idg , jfg and jmt acknowledge support from mcyt grant ( fed - er funds ) aya2002 - 00376 ( spain ) .
ga acknowledges support from junta de andaluca ( spain ) .
idg acknowledges the support of a calvo rods fellowship from the instituto nacional de tcnica aeroespacial and of the summer students program of the national radio astronomy observatory .
we present a study of the structure and dynamics of the star forming region b1-irs ( iras 03301 + 3057 ) using the properties of different molecules at high angular resolution ( @xmath04@xmath1 ) . 
 we have used vla observations of nh@xmath2 , ccs , and h@xmath3o masers at 1 cm . 
 ccs emission shows three clumps around the central source , with a velocity gradient from red to blueshifted velocities towards the protostar , probably due to the interaction with outflowing material . 
 water maser emission is elongated in the same direction as a reflection nebula detected at 2@xmath4 m by 2mass , with the maser spots located in a structure of some hundreds of au from the central source , possibly tracing a jet . 
 we propose a new outflow model to explain all our observations , consisting of a molecular outflow near the plane of the sky . 
 ammonia emission is extended and anticorrelated with ccs . 
 we have detected for the first time this anticorrelation at small scales ( 1400 au ) in a star forming region .