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CH3OH_II
BAR16 - European VLBI Network imaging of 6.7 GHz methanol masers
Interferometry data
Short title
: Bartkiewicz et al. (2016)
Authors
: Bartkiewicz, A. Szymczak, M. van Langevelde, H. J.
Journal
: Astronomy & Astrophysics, Volume 587, id.A104,
25
pp.
Bibcode
:
2016A&A...587A.104B
Target type
: Known_Class_II
Transitions
: CH3OH_6(II)
Abstract
Context. Methanol masers at 6.7 GHz are well known tracers of high-mass star-forming regions. However, their origin is still not clearly understood.
Aims: We aimed to determine the morphology and velocity structure for a large sample of the maser emission with generally lower peak flux densities than those in previous surveys.
Methods: Using the European VLBI Network (EVN) we imaged the remaining sources from a sample of sources that were selected from the unbiased survey using the Torun 32 m dish. In this paper we report the results for 17 targets. Together they form a database of a total of 63 source images with high sensitivity (3sigma
rms
= 15-30 mJy beam
-1
), milliarcsecond angular resolution (6-10 mas) and very good spectral resolution (0.09 km s
-1
or 0.18 km s
-1
) for detailed studies.
Results: We studied in detail the properties of the maser clouds and calculated the mean and median values of the projected size (17.4 ± 1.2 au and 5.5 au, respectively) as well as the FWHM of the line (0.373 ± 0.011 km s
-1
and 0.315 km s
-1
for the mean and median values, respectively), testing whether it was consistent with Gaussian profile. We also found maser clouds with velocity gradients (71%) that ranged from 0.005 km s
-1
au
-1
to 0.210 km s
-1
au
-1
. We tested the kinematic models to explain the observed structures of the 6.7 GHz emission. There were targets where the morphology supported the scenario of a rotating and expanding disk or a bipolar outflow. Comparing the interferometric and single-dish spectra we found that, typically, 50-70% of the flux was missing. This phenomena is not strongly related to the distance of the source.
Conclusions: The EVN imaging reveals that in the complete sample of 63 sources the ring-like morphology appeared in 17% of sources, arcs were seen in a further 8%, and the structures were complex in 46% cases. The ultra-compact (UC) H II regions coincide in position in the sky for 13% of the sources. They are related both to extremely high and low luminosity masers from the sample. The catalogue of the complete sample is available via
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Detection table from Bartkiewicz et al. (2016)
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individual components
Obs. RA
Obs. Dec
RA offset
Dec offset
#
Maser spot
Source name
V
peak
F
peak
(J2000)
(J2000)
(mas)
(mas)
(km/s)
(Jy)
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X
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
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2MASS K
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select MAX(met2_data_all.ra_hms) as ra_hms,MAX(met2_data_all.dec_dms) as dec_dms,MAX(met2_data_all.source_name) as source_name,MAX(met2_data_all.ra) as ra,MAX(met2_data_all.dec) as dec,MAX(met2_data_all.l) as l,MAX(met2_data_all.b) as b,MAX(met2_data_all.grp) as grp,MAX(met2_data_all.other_name) as other_name,MAX(met2_data_all.other_desc) as other_desc,BOOL_OR(thermal) as thermal,MAX(met2_data_all.line) as line,MAX(met2_data_all.vrange) as vrange,MAX(met2_data_all.vpeak) as vpeak,MAX(met2_data_all.peak) as peak,MAX(met2_data_all.fwhm) as fwhm,MAX(met2_data_all.int) as int,MAX(met2_data_all.rms) as rms,MAX(met2_data_all.units) as units,MAX(met2_data_all.units_rms) as units_rms,MAX(met2_data_all.date_txt) as date_txt,MAX(met2_data_all.telescope_ref) as telescope_ref,MAX(met2_data_all.telescope_conf) as telescope_conf,MAX(met2_data_all.v_step) as v_step,MAX(met2_data_all.beam) as beam,MAX(met2_data_all.beam_maj) as beam_maj,MAX(met2_data_all.beam_min) as beam_min,MAX(met2_data_all.beam_pa) as beam_pa,MAX(met2_data_all.ref) as ref,MAX(met2_data_all.list_ref) as list_ref,MAX(met2_data_all.ascii) as ascii,MAX(met2_data_all.url) as url,MAX(met2_data_all.image) as image,MAX(met2_data_all.image2) as image2,MAX(met2_data_all.image3) as image3,MAX(met2_data_all.descr) as descr,MAX(met2_data_all.id) as id,BOOL_OR(mjy_flag) as mjy_flag,BOOL_OR(rms_mjy_flag) as rms_mjy_flag,MAX(met2_data_all.dist) as dist,1 as dist_parallax,MAX(met2_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 met2_data_all LEFT JOIN all_objects_withmet ON met2_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 met2_data_all.line=transitions."Line" WHERE ref ilike 'BAR16' AND detected=true AND hide=false GROUP BY ref
select met2_data_all.ra_hms,met2_data_all.dec_dms,met2_data_all.source_name,met2_data_all.ra,met2_data_all.dec,met2_data_all.l,met2_data_all.b,met2_data_all.grp,met2_data_all.other_name,met2_data_all.other_desc,met2_data_all.thermal,met2_data_all.line,met2_data_all.vrange,met2_data_all.vpeak,met2_data_all.peak,met2_data_all.fwhm,met2_data_all.int,met2_data_all.rms,met2_data_all.units,met2_data_all.units_rms,met2_data_all.date_txt,met2_data_all.telescope_ref,met2_data_all.telescope_conf,met2_data_all.v_step,met2_data_all.beam,met2_data_all.beam_maj,met2_data_all.beam_min,met2_data_all.beam_pa,met2_data_all.ref,met2_data_all.list_ref,met2_data_all.ascii,met2_data_all.url,met2_data_all.image,met2_data_all.image2,met2_data_all.image3,met2_data_all.descr,met2_data_all.id,met2_data_all.mjy_flag,met2_data_all.rms_mjy_flag,met2_data_all.dist,met2_data_all.dist_parallax,met2_data_all.date_txt,line_det,type,simbad_types_cat FROM met2_data_all LEFT JOIN all_objects_withmet ON met2_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 met2_data_all.line=transitions."Line" WHERE ref ilike 'BAR16' AND detected=true AND hide=false ORDER BY detected DESC,id