J/AJ/140/968 A cluster of compact radio sources in W40 (Rodriguez+, 2010)
A cluster of compact radio sources in W40.
Rodriguez L.F., Rodney S.A., Reipurth B.
<Astron. J., 140, 968-972 (2010)>
=2010AJ....140..968R 2010AJ....140..968R
ADC_Keywords: H II regions ; Infrared sources ; Radio sources
Keywords: H II regions - infrared: stars -
open clusters and associations: individual (W40) -
radio continuum: stars - stars: formation
Abstract:
We present deep 3.6 cm radio continuum observations of the HII region
W40 obtained using the Very Large Array (VLA) in its A and B
configurations. We detect a total of 20 compact radio sources in a
region of 4'x4', with 11 of them concentrated in a band with 30" of
extent. We also present JHK photometry of the W40 cluster taken with
the QUIRC instrument on the University of Hawaii 2.2m telescope.
These data reveal that 15 of the 20 VLA sources have infrared
counterparts, and 10 show radio variability with periods less than 20
days. Based on these combined radio and IR data, we propose that eight
of the radio sources are candidate ultracompact HII regions, seven
are likely to be young stellar objects, and two may be shocked
interstellar gas.
Description:
We have used the Very Large Array (VLA) of the NRAO in its A and B
array configurations to observe W40 at 3.6cm, under the NRAO program
code AR551. The B configuration observations were made on 2003
November 3, while the A configuration observations were made on 2004
September 18.
The Infrared photometry was carried out with the QUick Infrared Camera
(QUIRC) on the University of Hawaii 2.2 m telescope from 2003 June
17-19. Data were obtained in the J, H, and K' filters of the Mauna Kea
Observatories (MKOs) filter set.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 59 271 Extended photometry table of W40 IR sources
table2.dat 70 20 Parameters of the 3.6 cm VLA sources
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- IR W40-IR sequential number
5- 12 F8.4 deg RAdeg Right Ascension in decimal degrees (J2000)
14- 20 F7.4 deg DEdeg Declination in decimal degrees (J2000)
22- 27 F6.3 mag Jmag MKO J-band magnitude
29- 33 F5.3 mag e_Jmag Error in Jmag
35- 40 F6.3 mag Hmag MKO H-band magnitude
42- 46 F5.3 mag e_Hmag Error in Hmag
48- 53 F6.3 mag Kmag MKO K'-band magnitude
55- 59 F5.3 mag e_Kmag Error in Kmag
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- VLA W40-VLA sequential number
4- 5 I2 h RAh Right ascension (J2000)
7- 8 I2 min RAm Right ascension (J2000)
10- 15 F6.3 s RAs Right ascension (J2000)
17 A1 --- DE- Declination sign (J2000)
18- 19 I2 deg DEd Declination (J2000)
21- 22 I2 arcmin DEm Declination (J2000)
24- 28 F5.2 arcsec DEs Declination (J2000)
30- 34 F5.2 mJy S3.6 Flux density at 3.6cm
36 A1 --- Var? [Y/N] Time variable?
37 A1 --- --- [(]
38 A1 --- l_var [≳ ] Limit flag on var
39- 42 F4.1 --- var [1/17]? Ratio between the largest and the
smallest flux density observed
43 A1 --- --- [)]
45- 49 F5.2 mag Jmag ?=- MKO J-band of the IR counterpart
51- 56 F6.3 mag Hmag ?=- MKO H-band of the IR counterpart
58- 62 F5.2 mag Kmag ?=- MKO K'-band of the IR counterpart
63 A1 --- n_Kmag [b] Magnitudes from 2MASS (1)
65- 70 A6 --- IRS W40-IRS designation, from Smith et al.
(1985ApJ...291..571S 1985ApJ...291..571S), IRS Na,
in Simbad
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Note (1): Source was saturated in shortest exposure. Magnitudes quoted here
are from 2MASS, translated to the MKO system.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 16-Jun-2012