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TOR14 - A very young, compact bipolar H₂O maser outflow in the intermediate-mass star-forming LkHÎ± 234 region

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Short title: Torrelles et al. (2014)
Authors: Torrelles, J. M. Curiel, S. Estalella, R. Anglada, G. Gómez, J. F. Cantó, J. Patel, N. A. Trinidad, M. A. Girart, J. M. Carrasco-González, C. Rodríguez, L. F.
Journal: Monthly Notices of the Royal Astronomical Society, Volume 442, Issue 1, p.148-159
Bibcode:

Target type: YSO
Transitions: H2O_22

Abstract
We report multi-epoch Very Long Baseline Interferometry (VLBI) H₂O maser observations towards the compact cluster of young stellar objects (YSOs) close to the Herbig Be star LkHα 234. This cluster includes LkHα 234 and at least nine more YSOs that are formed within projected distances of ∼ 10 arcsec (∼ 9000 au). We detect H₂O maser emission towards four of these YSOs. In particular, our VLBI observations (including proper motion measurements) reveal a remarkable very compact (∼ 0.2 arcsec = ∼ 180 au), bipolar H₂O maser outflow emerging from the embedded YSO Very Large Array (VLA) 2. We estimate a kinematic age of ∼ 40 yr for this bipolar outflow, with expanding velocities of ∼ 20 km s^-1 and momentum rate Ṁ_w V_w ≃ 10^-4-10^-3 M_⊙ yr^-1 km s^-1 × (Ω/4π), powered by a YSO of a few solar masses. We propose that the outflow is produced by recurrent episodic jet ejections associated with the formation of this YSO. Short-lived episodic ejection events have previously been found towards high-mass YSOs. We show now that this behaviour is also present in intermediate-mass YSOs. These short-lived episodic ejections are probably related to episodic increases in the accretion rate, as observed in low-mass YSOs. We predict the presence of an accretion disc associated with VLA 2. If detected, this would represent one of the few known examples of intermediate-mass stars with a disc-YSO-jet system at scales of a few hundred astronomical units.

Abstract

We report multi-epoch Very Long Baseline Interferometry (VLBI) H₂O maser observations towards the compact cluster of young stellar objects (YSOs) close to the Herbig Be star LkHα 234. This cluster includes LkHα 234 and at least nine more YSOs that are formed within projected distances of ∼ 10 arcsec (∼ 9000 au). We detect H₂O maser emission towards four of these YSOs. In particular, our VLBI observations (including proper motion measurements) reveal a remarkable very compact (∼ 0.2 arcsec = ∼ 180 au), bipolar H₂O maser outflow emerging from the embedded YSO Very Large Array (VLA) 2. We estimate a kinematic age of ∼ 40 yr for this bipolar outflow, with expanding velocities of ∼ 20 km s^-1 and momentum rate Ṁ_w V_w ≃ 10^-4-10^-3 M_⊙ yr^-1 km s^-1 × (Ω/4π), powered by a YSO of a few solar masses. We propose that the outflow is produced by recurrent episodic jet ejections associated with the formation of this YSO. Short-lived episodic ejection events have previously been found towards high-mass YSOs. We show now that this behaviour is also present in intermediate-mass YSOs. These short-lived episodic ejections are probably related to episodic increases in the accretion rate, as observed in low-mass YSOs. We predict the presence of an accretion disc associated with VLA 2. If detected, this would represent one of the few known examples of intermediate-mass stars with a disc-YSO-jet system at scales of a few hundred astronomical units.

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Detection table from Torrelles et al. (2014)

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ID	Obs. RA	Obs. Dec	RA offset	Dec offset	l	b	Group id	#	Source name	Image	Descr.	Line	V_peak	V_X	V_Y	F_peak	Telescope	V_step	RMS	Beam	Detection	Class	Dist. (parallax)	Date
	(J2000)	(J2000)	(mas)	(mas)	(deg.)	(deg.)						H₂O	(km/s)	(km/s)	(km/s)	(Jy)		(km/s)	(mJy/beam)	(arcsec)	Yes/No		(kpc)
1	+21 43 6.323	+66 06 55.92			105.415246	9.878487	G105.405+9.877		LkHa 234 VLA 2	Image	Descr	22 GHz;	-18.2 .. -8.7			0.08 .. 6.58	VLBA	0.21	25.000	0.0004	+H₂O -CH₃OH I -CH₃OH II	SFR_MIXED		2001 Dec. 2 - 2002 March 5
	+21 43 6.31243	+66 06 55.8343	-159.19 mas	-84.48 mas	105.415216	9.878481		1	LkHa 234 VLA 2				-12.5	-29.2 +- 0.1	-12.2 +- 0.4	0.36
	+21 43 6.31408	+66 06 55.8982	-134.35 mas	-20.55 mas	105.415230	9.878493		2	LkHa 234 VLA 2				-17.7	-14.0 +- 0.1	3.9 +- 0.3	0.4
	+21 43 6.31415	+66 06 55.9083	-133.3 mas	-10.51 mas	105.415232	9.878495		3	LkHa 234 VLA 2				-17.5	-12.9 +- 0.1	-2.1 +- 0.3	2.36
	+21 43 6.31418	+66 06 55.9078	-132.95 mas	-10.95 mas	105.415232	9.878495		4	LkHa 234 VLA 2				-18.2	-13.9 +- 0.2	-3.2 +- 0.6	0.09
	+21 43 6.31437	+66 06 55.8109	-130.09 mas	-107.94 mas	105.415214	9.878474		5	LkHa 234 VLA 2				-9.5	-21.6	-21.8	0.17
	+21 43 6.31444	+66 06 55.8027	-129 mas	-116.1 mas	105.415213	9.878472		6	LkHa 234 VLA 2				-11.6	-9.4 +- 0.1	-7.1 +- 0.1	0.16
	+21 43 6.3155	+66 06 55.7886	-113.12 mas	-130.15 mas	105.415212	9.878468		7	LkHa 234 VLA 2				-9.9	-20.5	-2	0.14
	+21 43 6.3158	+66 06 55.7859	-108.56 mas	-132.86 mas	105.415211	9.878467		8	LkHa 234 VLA 2				-9.3	-5.7	-4.4	0.12
	+21 43 6.31601	+66 06 55.7882	-105.51 mas	-130.59 mas	105.415212	9.878468		9	LkHa 234 VLA 2				-10.6	-3.4 +- 0.9	-5.5 +- 0.4	0.26
	+21 43 6.31608	+66 06 55.788	-104.42 mas	-130.83 mas	105.415212	9.878468		10	LkHa 234 VLA 2				-10.8	-1.4	-3.6	0.16
	+21 43 6.31624	+66 06 55.7886	-102.04 mas	-130.15 mas	105.415213	9.878468		11	LkHa 234 VLA 2				-10.6	-4.9	-6	0.09
	+21 43 6.31733	+66 06 55.8111	-85.68 mas	-107.66 mas	105.415218	9.878471		12	LkHa 234 VLA 2				-8.7	-13.7	-7.1	0.14
	+21 43 6.31741	+66 06 55.8409	-84.49 mas	-77.9 mas	105.415224	9.878477		13	LkHa 234 VLA 2				-13.5	-10.8 +- 1.3	-10.4 +- 1.1	0.09
	+21 43 6.3184	+66 06 55.7837	-69.59 mas	-135.08 mas	105.415214	9.878464		14	LkHa 234 VLA 2				-9.9	-6.3 +- 0.2	-7.0 +- 0.3	1.84
	+21 43 6.31853	+66 06 55.784	-67.62 mas	-134.82 mas	105.415215	9.878464		15	LkHa 234 VLA 2				-9.9	-8.3 +- 0.1	-8.1 +- 0.1	3.84
	+21 43 6.31858	+66 06 55.7841	-66.84 mas	-134.67 mas	105.415215	9.878464		16	LkHa 234 VLA 2				-9.9	-1.2 +- 0.1	-6.2 +- 0.1	6.58
	+21 43 6.31869	+66 06 55.7842	-65.22 mas	-134.56 mas	105.415215	9.878464		17	LkHa 234 VLA 2				-10.6	-3.7 +- 0.5	-5.8 +- 0.1	0.24
	+21 43 6.31874	+66 06 55.7845	-64.49 mas	-134.28 mas	105.415215	9.878464		18	LkHa 234 VLA 2				-10.6	1.7 +- 0.3	-6.9 +- 0.3	0.4
	+21 43 6.31878	+66 06 55.7846	-63.95 mas	-134.2 mas	105.415215	9.878464		19	LkHa 234 VLA 2				-10.6	5.0 +- 0.3	-5.8 +- 0.1	0.28
	+21 43 6.31975	+66 06 55.7899	-49.28 mas	-128.88 mas	105.415217	9.878464		20	LkHa 234 VLA 2				-11.2	-1.3	-4.2	0.08
	+21 43 6.33527	+66 06 56.0387	183.46 mas	119.9 mas	105.415284	9.878498		21	LkHa 234 VLA 2				-12.9	16.9 +- 1.3	11.9 +- 0.1	0.51
	+21 43 6.33638	+66 06 56.0424	200.1 mas	123.6 mas	105.415286	9.878498		22	LkHa 234 VLA 2				-8.9	15.0 +- 0.8	0.0 +- 1.5	0.19
	+21 43 6.33686	+66 06 56.0136	207.28 mas	94.83 mas	105.415281	9.878491		23	LkHa 234 VLA 2				-9.5	24.2	-1.1	0.11
	+21 43 6.33687	+66 06 56.0128	207.45 mas	94.04 mas	105.415281	9.878491		24	LkHa 234 VLA 2				-9.7	21.3	19.4	0.14
	+21 43 6.33687	+66 06 56.0119	207.52 mas	93.1 mas	105.415281	9.878491		25	LkHa 234 VLA 2				-9.3	20.4 +- 0.4	15.3 +- 1.1	0.12
	+21 43 6.33689	+66 06 55.996	207.7 mas	77.21 mas	105.415278	9.878488		26	LkHa 234 VLA 2				-14.8	26.8 +- 0.3	13.4 +- 0.6	0.16
	+21 43 6.33694	+66 06 55.9931	208.51 mas	74.28 mas	105.415277	9.878487		27	LkHa 234 VLA 2				-13.3	24.8 +- 0.1	7.3 +- 0.1	0.18
	+21 43 6.33695	+66 06 55.9964	208.65 mas	77.64 mas	105.415278	9.878488		28	LkHa 234 VLA 2				-11	31.5 +- 3.8	6.4 +- 2.0	0.11
	+21 43 6.33695	+66 06 55.9956	208.68 mas	76.81 mas	105.415278	9.878487		29	LkHa 234 VLA 2				-12.5	23.7 +- 0.3	13.5 +- 0.8	0.24
	+21 43 6.33698	+66 06 55.9975	209.11 mas	78.74 mas	105.415278	9.878488		30	LkHa 234 VLA 2				-12.7	28	13.6	0.3
	+21 43 6.33699	+66 06 55.9936	209.18 mas	74.79 mas	105.415277	9.878487		31	LkHa 234 VLA 2				-12.7	24.5 +- 0.2	7.1 +- 0.2	0.18
	+21 43 6.33706	+66 06 55.9962	210.33 mas	77.37 mas	105.415278	9.878487		32	LkHa 234 VLA 2				-11.6	24.6	15.2	0.26
2	+21 43 6.323	+66 06 55.92			105.415246	9.878487	G105.405+9.877		LkHa 234 VLA 3A			22 GHz;	-36.9			0.09	VLBA	0.21	25.000	0.0004	+H₂O -CH₃OH I -CH₃OH II	SFR_MIXED		2001 Dec. 2 - 2002 March 5
	+21 43 6.38605	+66 06 55.002	945.19 mas	-916.78 mas	105.415155	9.878226		1	LkHa 234 VLA 3A				-36.9	9.7	39.9	0.09
3	+21 43 6.323	+66 06 55.92			105.415246	9.878487	G105.405+9.877		LkHa 234 VLA 3B			22 GHz;	-5.7 .. -4.7			0.17 .. 1.33	VLBA	0.21	25.000	0.0004	+H₂O -CH₃OH I -CH₃OH II	SFR_MIXED		2001 Dec. 2 - 2002 March 5
	+21 43 6.38159	+66 06 55.1844	878.3 mas	-734.44 mas	105.415184	9.878269		1	LkHa 234 VLA 3B				-4.7	-3.9	-5.8	0.17
	+21 43 6.38161	+66 06 55.1835	878.59 mas	-735.32 mas	105.415184	9.878268		2	LkHa 234 VLA 3B				-5.7	-1.2 +- 0.3	4.4 +- 0.3	1.33
4	+21 43 6.323	+66 06 55.92			105.415246	9.878487	G105.405+9.877		LkHa 234 VLA 3 (A/B)			22 GHz;	-20.9 .. -18.2			0.1 .. 1.2	VLBA	0.21	25.000	0.0004	+H₂O -CH₃OH I -CH₃OH II	SFR_MIXED		2001 Dec. 2 - 2002 March 5
	+21 43 6.37782	+66 06 55.0624	821.72 mas	-856.41 mas	105.415156	9.878247		1	LkHa 234 VLA 3 (A/B)				-20.9	6.0 +- 0.4	-6.5 +- 0.1	0.11
	+21 43 6.3779	+66 06 55.0623	822.91 mas	-856.48 mas	105.415156	9.878247		2	LkHa 234 VLA 3 (A/B)				-20.5	-8.6	-2.6	0.18
	+21 43 6.37796	+66 06 55.0627	823.82 mas	-856.07 mas	105.415156	9.878247		3	LkHa 234 VLA 3 (A/B)				-20.1	-3.7 +- 0.2	-10.5 +- 0.5	0.16
	+21 43 6.37805	+66 06 55.0626	825.18 mas	-856.18 mas	105.415156	9.878247		4	LkHa 234 VLA 3 (A/B)				-19.8	-0.6 +- 0.5	-9.0 +- 0.2	0.98
	+21 43 6.37812	+66 06 55.0619	826.24 mas	-856.85 mas	105.415156	9.878247		5	LkHa 234 VLA 3 (A/B)				-19.6	-3.6	-0.3	0.1
	+21 43 6.37813	+66 06 55.0648	826.41 mas	-853.99 mas	105.415157	9.878248		6	LkHa 234 VLA 3 (A/B)				-18.2	-2.2 +- 0.1	-6.1 +- 0.1	1.2

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 'TOR14' 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 'TOR14' AND detected=true AND hide=false ORDER BY detected DESC,id

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TOR14 - A very young, compact bipolar H2O maser outflow in the intermediate-mass star-forming LkHÎ± 234 region

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Detection table from Torrelles et al. (2014)

TOR14 - A very young, compact bipolar H₂O maser outflow in the intermediate-mass star-forming LkHÎ± 234 region