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KIM13B - Evolution of the Water Maser Expanding Shell in W75N VLA 2

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Short title: Kim et al. (2013B)
Authors: Kim Jeong-Sook, Kim Soon-Wook, Kurayama Tomoharu, Honma Mareki, Sasao Tesuo, Surcis Gabriele, Canto Jorge, Torrelles Jose M., Kim Sang Joon
Journal: The Astrophysical Journal, Volume 767, Issue 1, article id. 86, 9 pp. (2013).
Bibcode:

Target type: High_mass_SFR
Transitions: H2O_22

Abstract
We present Very Long Baseline Interferometry (VLBI) observations of 22 GHz H₂O masers in the high-mass star-forming region of W75N, carried out with VLBI Exploration of Radio Astrometry (VERA) for three epochs in 2007 with an angular resolution of ~1 mas. We detected H₂O maser emission toward the radio jet in VLA 1 and the expanding shell-like structure in VLA 2. The spatial distribution of the H₂O masers detected with VERA and measured proper motions around VLA 1 and VLA 2 are similar to those found with previous VLBI observations in epochs 1999 and 2005, with the masers in VLA 1 mainly distributed along a linear structure parallel to the radio jet and, on the other hand, forming a shell-like structure around VLA 2. We have made elliptical fits to the VLA 2 H₂O maser shell-like structure observed in the different epochs (1999, 2005, and 2007), and found that the shell is still expanding eight years after its discovery. From the difference in the size of the semi-major axes of the fitted ellipses in epochs 1999 (sime71 ± 1 mas), 2005 (sime97 ± 3 mas), and 2007 (sime111 ± 1 mas), we estimate an average expanding velocity of ~5 mas yr^-1, similar to the proper motions measured in the individual H₂O maser features. A kinematic age of ~20 yr is derived for this structure. In addition, our VERA observations indicate an increase in the ellipticity of the expanding shell around VLA 2 from epochs 1999 to 2007. In fact, the elliptical fit of the VERA data shows a ratio of the minor and major axes of ~0.6, in contrast with an almost circular shape for the shell detected in 1999 and 2005 (b/a ~ 0.9). This suggests that we are probably observing the formation of a jet-driven H₂O maser structure in VLA2, evolving from a non-collimated pulsed-outflow event during the first stages of evolution of a massive young stellar object (YSO). This may support predictions made earlier by other authors on this issue, consistent with recent magnetohydrodynamical simulations. We discuss possible implications of our results in the study of the first stages of evolution of massive YSOs.

Abstract

We present Very Long Baseline Interferometry (VLBI) observations of 22 GHz H₂O masers in the high-mass star-forming region of W75N, carried out with VLBI Exploration of Radio Astrometry (VERA) for three epochs in 2007 with an angular resolution of ~1 mas. We detected H₂O maser emission toward the radio jet in VLA 1 and the expanding shell-like structure in VLA 2. The spatial distribution of the H₂O masers detected with VERA and measured proper motions around VLA 1 and VLA 2 are similar to those found with previous VLBI observations in epochs 1999 and 2005, with the masers in VLA 1 mainly distributed along a linear structure parallel to the radio jet and, on the other hand, forming a shell-like structure around VLA 2. We have made elliptical fits to the VLA 2 H₂O maser shell-like structure observed in the different epochs (1999, 2005, and 2007), and found that the shell is still expanding eight years after its discovery. From the difference in the size of the semi-major axes of the fitted ellipses in epochs 1999 (sime71 ± 1 mas), 2005 (sime97 ± 3 mas), and 2007 (sime111 ± 1 mas), we estimate an average expanding velocity of ~5 mas yr^-1, similar to the proper motions measured in the individual H₂O maser features. A kinematic age of ~20 yr is derived for this structure. In addition, our VERA observations indicate an increase in the ellipticity of the expanding shell around VLA 2 from epochs 1999 to 2007. In fact, the elliptical fit of the VERA data shows a ratio of the minor and major axes of ~0.6, in contrast with an almost circular shape for the shell detected in 1999 and 2005 (b/a ~ 0.9). This suggests that we are probably observing the formation of a jet-driven H₂O maser structure in VLA2, evolving from a non-collimated pulsed-outflow event during the first stages of evolution of a massive young stellar object (YSO). This may support predictions made earlier by other authors on this issue, consistent with recent magnetohydrodynamical simulations. We discuss possible implications of our results in the study of the first stages of evolution of massive YSOs.

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Detection table from Kim et al. (2013B)

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ID	Obs. RA	Obs. Dec	RA offset	Dec offset	l	b	Group id	#	Source name	Image	Descr.	Line	V_peak	Telescope	V_step	RMS	Beam	Detection	Class	Dist. (parallax)	Date
	(J2000)	(J2000)	(mas)	(mas)	(deg.)	(deg.)						H₂O	(km/s)		(km/s)	(Jy/beam)	(arcsec)	Yes/No		(kpc)
1	+20 38 36.49	+42 37 34.3			81.871269	0.780402	G81.871+0.781		W75N VLA 1	Image	Descr	22 GHz;	10.62 .. 12.52	VERA	0.21	2.000	0.0014 x 0.0009	+H₂O +OH	SFR_MIXED		2007 Jan 20 - 2007 May 29
	+20 38 36.4435	+42 37 34.7661	-699.3 mas	467.7 mas	81.871286	0.780594		1	W75N VLA 1				12.52
	+20 38 36.4435	+42 37 34.7662	-699.3 mas	467.8 mas	81.871286	0.780594		2	W75N VLA 1				12.3
	+20 38 36.4435	+42 37 34.7663	-699.3 mas	467.9 mas	81.871286	0.780594		3	W75N VLA 1				12.09
	+20 38 36.4431	+42 37 34.7065	-704.2 mas	408.1 mas	81.871272	0.780585		4	W75N VLA 1				11.67
	+20 38 36.4431	+42 37 34.7064	-704.3 mas	408 mas	81.871272	0.780585		5	W75N VLA 1				11.46
	+20 38 36.4431	+42 37 34.7065	-704.4 mas	408.1 mas	81.871272	0.780585		6	W75N VLA 1				11.25
	+20 38 36.4431	+42 37 34.7065	-704.4 mas	408.1 mas	81.871272	0.780585		7	W75N VLA 1				11.04
	+20 38 36.4431	+42 37 34.7066	-704.4 mas	408.2 mas	81.871272	0.780585		8	W75N VLA 1				10.83
	+20 38 36.4431	+42 37 34.7066	-704.4 mas	408.2 mas	81.871272	0.780585		9	W75N VLA 1				10.62
2	+20 38 36.49	+42 37 34.3			81.871269	0.780402	G81.871+0.781		W75N VLA 2			22 GHz;	4.93 .. 15.25	VERA	0.21	2.000	0.0014 x 0.0009	+H₂O +OH	SFR_MIXED		2007 Jan 20 - 2007 May 29
	+20 38 36.4901	+42 37 34.2983	0 mas	-0.1 mas	81.871269	0.780402		1	W75N VLA 2				8.09
	+20 38 36.4901	+42 37 34.2984	0 mas	0 mas	81.871269	0.780402		2	W75N VLA 2				7.88
	+20 38 36.4901	+42 37 34.2987	-0.3 mas	0.3 mas	81.871269	0.780402		3	W75N VLA 2				7.04
	+20 38 36.4912	+42 37 34.2791	16.3 mas	-19.3 mas	81.871267	0.780396		4	W75N VLA 2				15.25
	+20 38 36.4911	+42 37 34.2794	16 mas	-19 mas	81.871267	0.780396		5	W75N VLA 2				15.04
	+20 38 36.4911	+42 37 34.2795	15.7 mas	-18.9 mas	81.871267	0.780396		6	W75N VLA 2				14.83
	+20 38 36.4911	+42 37 34.2797	15.6 mas	-18.7 mas	81.871267	0.780396		7	W75N VLA 2				14.62
	+20 38 36.4901	+42 37 34.2978	0.5 mas	-0.6 mas	81.871269	0.780402		8	W75N VLA 2				8.93
	+20 38 36.4901	+42 37 34.2979	0.4 mas	-0.5 mas	81.871269	0.780402		9	W75N VLA 2				8.72
	+20 38 36.4901	+42 37 34.298	0.4 mas	-0.4 mas	81.871269	0.780402		10	W75N VLA 2				8.51
	+20 38 36.4901	+42 37 34.2982	0.2 mas	-0.2 mas	81.871269	0.780402		11	W75N VLA 2				8.3
	+20 38 36.4901	+42 37 34.2985	0 mas	0.1 mas	81.871269	0.780402		12	W75N VLA 2				7.67
	+20 38 36.4901	+42 37 34.2986	-0.1 mas	0.2 mas	81.871269	0.780402		13	W75N VLA 2				7.46
	+20 38 36.4901	+42 37 34.2986	-0.1 mas	0.2 mas	81.871269	0.780402		14	W75N VLA 2				7.25
	+20 38 36.4901	+42 37 34.2977	0.9 mas	-0.7 mas	81.871269	0.780402		15	W75N VLA 2				9.36
	+20 38 36.4901	+42 37 34.2979	0.7 mas	-0.5 mas	81.871269	0.780402		16	W75N VLA 2				9.14
	+20 38 36.4901	+42 37 34.298	0.5 mas	-0.4 mas	81.871269	0.780402		17	W75N VLA 2				8.93
	+20 38 36.4796	+42 37 34.1491	-157.3 mas	-149.3 mas	81.871217	0.780402		18	W75N VLA 2				12.3
	+20 38 36.4796	+42 37 34.1491	-157.4 mas	-149.3 mas	81.871217	0.780402		19	W75N VLA 2				12.09
	+20 38 36.4796	+42 37 34.1489	-157.5 mas	-149.5 mas	81.871217	0.780402		20	W75N VLA 2				11.88
	+20 38 36.4796	+42 37 34.1488	-157.6 mas	-149.6 mas	81.871217	0.780402		21	W75N VLA 2				11.67
	+20 38 36.4796	+42 37 34.1487	-157.5 mas	-149.7 mas	81.871217	0.780402		22	W75N VLA 2				11.46
	+20 38 36.4835	+42 37 34.1305	-98.3 mas	-167.9 mas	81.871220	0.780389		23	W75N VLA 2				9.99
	+20 38 36.4835	+42 37 34.1305	-98.3 mas	-167.9 mas	81.871220	0.780389		24	W75N VLA 2				9.57
	+20 38 36.4835	+42 37 34.1305	-98.3 mas	-167.9 mas	81.871220	0.780389		25	W75N VLA 2				9.36
	+20 38 36.4835	+42 37 34.1305	-98.3 mas	-167.9 mas	81.871220	0.780389		26	W75N VLA 2				9.57
	+20 38 36.4835	+42 37 34.1305	-98.3 mas	-167.9 mas	81.871220	0.780389		27	W75N VLA 2				9.36
	+20 38 36.4847	+42 37 34.1257	-81.3 mas	-172.7 mas	81.871221	0.780386		28	W75N VLA 2				5.98
	+20 38 36.4812	+42 37 34.2516	-133.9 mas	-46.8 mas	81.871242	0.780416		29	W75N VLA 2				5.35
	+20 38 36.4812	+42 37 34.2517	-133.7 mas	-46.7 mas	81.871242	0.780416		30	W75N VLA 2				5.14
	+20 38 36.4811	+42 37 34.2517	-134.1 mas	-46.7 mas	81.871242	0.780416		31	W75N VLA 2				4.93

DSS colored	2MASS colored	WISE colored
SDSS color	IRAC color I1,I2,I4	GLIMPSE 360
PACS color (70-160 um)	SPIRE color (250-500 um)	NVSS (1.4GHz)
ATLASGAL 870 um	ATLASGAL 870 um + Planck	Bolocam 1.1 mm
UKIDSS K Download UKIDSS K FITS	2MASS K Download 2MASS K FITS

select MAX(h2o_data_all.ra_hms) as ra_hms,MAX(h2o_data_all.dec_dms) as dec_dms,MAX(h2o_data_all.source_name) as source_name,MAX(h2o_data_all.ra) as ra,MAX(h2o_data_all.dec) as dec,MAX(h2o_data_all.l) as l,MAX(h2o_data_all.b) as b,MAX(h2o_data_all.grp) as grp,MAX(h2o_data_all.other_name) as other_name,MAX(h2o_data_all.other_desc) as other_desc,BOOL_OR(thermal) as thermal,MAX(h2o_data_all.line) as line,MAX(h2o_data_all.vrange) as vrange,MAX(h2o_data_all.vpeak) as vpeak,MAX(h2o_data_all.peak) as peak,MAX(h2o_data_all.fwhm) as fwhm,MAX(h2o_data_all.int) as int,MAX(h2o_data_all.rms) as rms,MAX(h2o_data_all.units) as units,MAX(h2o_data_all.units_rms) as units_rms,MAX(h2o_data_all.date_txt) as date_txt,MAX(h2o_data_all.telescope_ref) as telescope_ref,MAX(h2o_data_all.telescope_conf) as telescope_conf,MAX(h2o_data_all.v_step) as v_step,MAX(h2o_data_all.beam) as beam,MAX(h2o_data_all.beam_maj) as beam_maj,MAX(h2o_data_all.beam_min) as beam_min,MAX(h2o_data_all.beam_pa) as beam_pa,MAX(h2o_data_all.ref) as ref,MAX(h2o_data_all.list_ref) as list_ref,MAX(h2o_data_all.ascii) as ascii,MAX(h2o_data_all.url) as url,MAX(h2o_data_all.image) as image,MAX(h2o_data_all.image2) as image2,MAX(h2o_data_all.image3) as image3,MAX(h2o_data_all.descr) as descr,MAX(h2o_data_all.id) as id,BOOL_OR(mjy_flag) as mjy_flag,BOOL_OR(rms_mjy_flag) as rms_mjy_flag,MAX(h2o_data_all.dist) as dist,1 as dist_parallax,MAX(h2o_data_all.date_txt) as date_txt,MAX(line_det) as line_det,MAX(type) as type,MAX(simbad_types_cat) as simbad_types_cat FROM h2o_data_all  LEFT JOIN all_objects_withmet ON h2o_data_all.grp=all_objects_withmet.group_name LEFT JOIN object_categories ON all_objects_withmet.group_name = object_categories.group_name_cat AND object_categories.tbl_cat = 'all_objects_withmet' LEFT JOIN transitions ON h2o_data_all.line=transitions."Line"  WHERE ref ilike 'KIM13B' AND detected=true AND hide=false GROUP BY ref

select h2o_data_all.ra_hms,h2o_data_all.dec_dms,h2o_data_all.source_name,h2o_data_all.ra,h2o_data_all.dec,h2o_data_all.l,h2o_data_all.b,h2o_data_all.grp,h2o_data_all.other_name,h2o_data_all.other_desc,h2o_data_all.thermal,h2o_data_all.line,h2o_data_all.vrange,h2o_data_all.vpeak,h2o_data_all.peak,h2o_data_all.fwhm,h2o_data_all.int,h2o_data_all.rms,h2o_data_all.units,h2o_data_all.units_rms,h2o_data_all.date_txt,h2o_data_all.telescope_ref,h2o_data_all.telescope_conf,h2o_data_all.v_step,h2o_data_all.beam,h2o_data_all.beam_maj,h2o_data_all.beam_min,h2o_data_all.beam_pa,h2o_data_all.ref,h2o_data_all.list_ref,h2o_data_all.ascii,h2o_data_all.url,h2o_data_all.image,h2o_data_all.image2,h2o_data_all.image3,h2o_data_all.descr,h2o_data_all.id,h2o_data_all.mjy_flag,h2o_data_all.rms_mjy_flag,h2o_data_all.dist,h2o_data_all.dist_parallax,h2o_data_all.date_txt,line_det,type,simbad_types_cat FROM h2o_data_all   LEFT JOIN all_objects_withmet ON h2o_data_all.grp=all_objects_withmet.group_name LEFT JOIN object_categories ON all_objects_withmet.group_name = object_categories.group_name_cat AND object_categories.tbl_cat = 'all_objects_withmet' LEFT JOIN transitions ON h2o_data_all.line=transitions."Line"  WHERE ref ilike 'KIM13B' AND detected=true AND hide=false ORDER BY detected DESC,id

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KIM13B - Evolution of the Water Maser Expanding Shell in W75N VLA 2

Interferometry data

View as list of objects

Detection table from Kim et al. (2013B)