J/A+A/550/A21 Massive star-forming regions radio lines (Sanchez-Monge+, 2013)
Different evolutionary stages in massive star formation. Centimeter continuum
and H2O maser emission with ATCA.
Sanchez-Monge A., Beltran M.T., Cesaroni R., Fontani F., Brand J.,
Molinari S., Testi L., Burton M.
<Astron. Astrophys. 550, A21 (2013)>
=2013A&A...550A..21S 2013A&A...550A..21S
ADC_Keywords: H II regions ; Interstellar medium ; Masers ; Radio continuum ;
Stars, OB
Keywords: stars: formation - stars: massive - HII regions -
radio continuum: ISM - masers
Abstract:
We present Australia Telescope Compact Array (ATCA) observations of
the H2O maser line and radio continuum at 18.0GHz and 22.8GHz toward
a sample of 192 massive star-forming regions containing several clumps
already imaged at 1.2mm. The main aim of this study is to investigate
the water maser and centimeter continuum emission (that likely traces
thermal free-free emission) in sources at different evolutionary
stages, using evolutionary classifications previously published. We
used the recently comissioned Compact Array Broadband Backend (CABB)
at ATCA that obtains images with 20arcsec resolution in the 1.3cm
continuum and H2O maser emission in all targets. For the
evolutionary analysis of the sources we used millimeter continuum
emission from the literature and the infrared emission from the MSX
Point Source Catalog. We detect centimeter continuum emission in 88%
of the observed fields with a typical rms noise level of 0.45mJy/beam.
Most of the fields show a single radio continuum source, while in 20%
of them we identify multiple components. A total of 214 centimeter
continuum sources have been identified, that likely trace optically
thin HII regions, with physical parameters typical of both extended
and compact HII regions. Water maser emission was detected in 41% of
the regions, resulting in a total of 85 distinct components. The low
angular (20arcsec) and spectral (14km/s) resolutions do not allow a
proper analysis of the water maser emission, but suffice to
investigate its association with the continuum sources. We have also
studied the detection rate of HII regions in the two types of IRAS
sources defined in the literature on the basis of the IRAS colors:
High and Low. No significant differences are found, with high
detection rates (>90%) for both High and Low sources. We classify the
millimeter and infrared sources in our fields in three evolutionary
stages following the scheme presented previously: (Type 1)
millimeter-only sources, (Type 2) millimeter plus infrared sources,
(Type 3) infrared-only sources. We find that HII regions are mainly
associated with Type 2 and Type 3 objects, confirming that these are
more evolved than Type 1 sources. The HII regions associated with Type
3 sources are slightly less dense and larger in size than those
associated with Type 2 sources, as expected if the HII region expands
as it evolves, and Type 3 objects are older than Type 2 objects. The
maser emission is mostly found to be associated with Type 1 and Type 2
sources, with a higher detection rate toward Type 2, consistent with
the results of the literature. Finally, our results on HII region and
H2O maser association with different evolutionary types confirm the
evolutionary classification proposed previously.
Description:
Physical parameters of 238 HII regions and 78 water masers detected in
192 fields around IRAS sources. For each observed region the name,
type, distance, equatorial and galactic coordinates and synthesized
beams at 18.0 and 22.8GHz are given. For the detected centimeter
continuum sources the name, coordinates, intensity and size are given,
as well as the physical parameters derived assuming the emission comes
from optically thin HII regions (size, brightness temperature,
electron density, emission measure, mass of ionized gas, Lyman
continuum, spectral type of the ionizing source, spectral index).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
obs.dat 118 192 Target fields observed with ATCA at 18.0GHz
and 22.8GHz (table1)
cm.dat 99 238 ATCA centimeter continuum sources at 18.0GHz
and 22.8GHz (table3)
masers.dat 63 85 Water masers detected (table4)
hii.dat 96 238 Physical parameters of optically thin HII regions,
and spectral indices (table5)
type1.dat 67 183 Sources classified as Type 1 objects (table7)
type2.dat 104 132 Sources classified as Type 2 objects (table8)
type3.dat 70 197 Sources classified as Type 3 objects (table9)
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See also:
J/A+A/447/221 : Dust continuum emission from IRAS sources (Beltran+, 2006)
Byte-by-byte Description of file: obs.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Region Name of the region with IRAS source name,
HHMMm+DDMM_N (G1)
15 A1 --- Type [H/L] High/Low IRAS source (1)
18- 21 F4.1 kpc Dist ? Distance
25- 26 I2 h RAh Right ascension (J2000.0)
28- 29 I2 min RAm Right ascension (J2000.0)
31- 35 F5.2 s RAs Right ascension (J2000.0)
37 A1 --- DE- Declination sign (J2000.0)
38- 39 I2 deg DEd Declination (J2000.0)
41- 42 I2 arcmin DEm Declination (J2000.0)
44- 47 F4.1 arcsec DEs Declination (J2000.0)
51- 56 F6.2 deg GLON Galactic longitude
58- 62 F5.2 deg GLAT Galactic latitude
66- 69 F4.1 arcsec bmaj18 Major axis of synthesized beam at 18.0GHz
71- 74 F4.1 arcsec bmin18 Minor axis of synthesized beam at 18.0GHz
76- 78 I3 deg bPA18 [-90/90] Position angle of synthesized beam
at 18.0GHz
80- 87 F8.6 Jy rms18 rms noise level at 18.0GHz (in Jy/beam)
91- 94 F4.1 arcsec bmaj22 Major axis of synthesized beam at 22.8GHz
96- 99 F4.1 arcsec bmin22 Minor axis of synthesized beam at 22.8GHz
101-103 I3 deg bPA22 [-90/90] Position angle of synthesized beam
at 22.8GHz
105-112 F8.6 Jy rms22 rms noise level at 22.8GHz (in Jy/beam)
116-118 A3 --- Date Day of observation (2)
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Note (1): H (High) or L (Low) IRAS source according to the classification
of Palla et al (1991A&A...246..249P 1991A&A...246..249P).
Note (2): Date code as follows:
25J = July 25 2009
26J = July 26 2009
09O = October 09 2009
10O = October 10 2009
00J = July 25 and 26 2009
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Byte-by-byte Description of file: cm.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 A12 --- Region Name of the region with IRAS source name,
HHMMm+DDMM_N (G1) (1)
16 I1 --- Seqc [1/4]? ATCA source number
19- 20 I2 h RAh ? Right ascension (J2000.0)
22- 23 I2 min RAm ? Right ascension (J2000.0)
25- 28 F4.1 s RAs ? Right ascension (J2000.0)
30 A1 --- DE- Declination sign (J2000.0)
31- 32 I2 deg DEd ? Declination (J2000.0)
34- 35 I2 arcmin DEm ? Declination (J2000.0)
37- 40 F4.1 arcsec DEs ? Declination (J2000.0)
44 A1 --- l_Ipeak18 Limit flag on intensity at 18.0GHz
45- 50 F6.4 Jy Ipeak18 Primary beam corrected intensity at 18.0GHz
(in Jy/beam)
52- 57 F6.4 Jy Flux18 ? Primary beam corrected flux density at 18.0GHz
59- 62 F4.1 arcsec FWHP18 ? full width at half power at 18.0GHz
64 A1 --- l_Size18 Limit flag on size at 18.0GHz
65- 68 F4.1 arcsec Size18 ? deconvolved size at 18.0GHz
71 A1 --- l_Ipeak22 Limit flag on intensity at 22.8GHz
72- 77 F6.4 Jy Ipeak22 Primary beam corrected intensity at 22.8GHz
(in Jy/beam)
79- 84 F6.4 Jy Flux22 ? Primary beam corrected flux density at 22.8GHz
86- 89 F4.1 arcsec FWHP22 ? full width at half power at 22.8GHz
91 A1 --- l_Size22 ? Limit flag on size at 22.8GHz
92- 95 F4.1 arcsec Size22 ? deconvolved size at 22.8GHz
99 A1 --- Maser [Y ] Association with water maser
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Note (1): 16061-5048_1 there is a centimeter continuum source already
detected in the fields 08477-4359_0, 15278-5620_0, 15470-5419_0,
15470-5419_0, and 16061-5048_4 respectively
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Byte-by-byte Description of file: masers.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- SeqM Number of water maser component
4- 15 A12 --- Region Name of the region with IRAS source name,
HHMMm+DDMM_N (G1)
19- 20 I2 h RAh Right ascension (J2000.0)
22- 23 I2 min RAm Right ascension (J2000.0)
25- 30 F6.3 s RAs Right ascension (J2000.0)
32 A1 --- DE- Declination sign (J2000.0)
33- 34 I2 deg DEd Declination (J2000.0)
36- 37 I2 arcmin DEm Declination (J2000.0)
39- 43 F5.2 arcsec DEs Declination (J2000.0)
47- 56 E10.4 Jy.km/s FluxdV Integrated flux over the whole velocity range
60- 63 I4 km/s Vpeak Velocity of the water maser component
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Byte-by-byte Description of file: hii.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Region Name of the region with IRAS source name,
HHMMm+DDMM_N (G1)
15 I1 --- SeqHII ? ATCA source number
18- 21 F4.1 GHz Freq ? Frequency used to derive physical parameters
24- 27 F4.1 kpc Dist ? Distance
29 A1 --- l_Radius Limit flag on radius
30- 34 F5.3 pc Radius ? Radius of the HII region
36 A1 --- l_Tb Limit flag on brightness temperature
37- 44 E8.2 K Tb ? Brightness temperature of the HII region
46 A1 --- l_ne Limit flag on electron density
47- 54 E8.2 1/cm+3 ne ? Electron density of the HII region
56 A1 --- l_EM Limit flag on emission measure
57- 64 E8.2 pc/cm+6 EM ? Emission measure of the HII region
66 A1 --- l_Mi Limit flag on mass of ionized gas
67- 74 E8.2 Msun Mi ? Mass of ionized gas
77- 81 F5.2 [s-1] logNLy ? logarithmic Lyman continuum luminosity
84- 87 A4 --- SpType MK spectral type of the ionizing ZAMS star
91- 96 F6.1 --- SpIndex ? Spectral index α between 18.0GHz and
22.8GHz (Sν∝να)
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Byte-by-byte Description of file: type1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- IRASm IRAS field containing the millimeter source
13- 14 I2 --- Seqm Number of the millimeter source (G2)
17- 23 F7.3 deg RAmdeg Millimeter source Righ Ascension (J2000.0)
26- 32 F7.3 deg DEmdeg Millimeter source Declination (J2000.0)
35- 46 A12 --- IRASc IRAS field containing the centimeter source
49 I1 --- Seqc ? Number of the centimeter source (G3)
52- 63 A12 --- IRASM IRAS field containing the water maser
66- 67 I2 --- SeqM ? Number of the water maser (G4)
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Byte-by-byte Description of file: type2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- IRASm IRAS field containing the millimeter source
13- 14 I2 --- Seqm Number of the millimeter source (G2)
17- 23 F7.3 deg RAmdeg Millimeter source Righ Ascension (J2000.0)
26- 32 F7.3 deg DEmdeg Millimeter source Declination (J2000.0)
35- 51 A17 --- SeqX Name of the MSX source
54- 60 F7.3 deg RAXdeg MSX Righ Ascension (J2000.0)
63- 69 F7.3 deg DEXdeg MSX Declination (J2000.0)
72- 83 A12 --- IRASc IRAS field containing the centimeter source
86 I1 --- Seqc ? Number of the centimeter source (G3)
89-100 A12 --- IRASM IRAS field containing the water maser
103-104 I2 --- SeqM ? Number of the water maser (G4)
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Byte-by-byte Description of file: type3.dat
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Bytes Format Units Label Explanations
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1- 17 A17 --- SeqX Name of the MSX source
20- 26 F7.3 deg RAXdeg MSX Righ Ascension (J2000.0)
29- 35 F7.3 deg DEXdeg MSX Declination (J2000.0)
38- 49 A12 --- IRASc IRAS field containing the centimeter source
52 I1 --- Seqc ? Number of the centimeter source (G3)
55- 66 A12 --- IRASM IRAS field containing the water maser
69- 70 I2 --- SeqM ? Number of the water maser (G4)
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Global notes:
Note (G1): If the second number (after _) if equal to 0: phase center
corresponding to the IRAS source; if different to 0: phase center
corresponding to the millimeter clump detected by Beltran et al.
(2006, Cat. J/A+A/447/221).
Note (G2): The number corresponds to the millimeter clump detected by
Beltran et al. (2006, Cat. J/A+A/447/221).
Note (G3): The number corresponds to the number listed in cm.dat file.
Note (G4): The number corresponds to the water maser number listed in
maser.dat file.
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Acknowledgements:
Alvaro Sanchez-Monge, asanchez(at)arcetri.astro.it
(End) Alvaro Sanchez-Monge [Arcetri, Italy], Patricia Vannier [CDS] 27-Nov-2012