J/A+A/619/A124 THOR survey in northern Galactic plane (Wang+, 2018)
Radio continuum emission in the northern Galactic plane:
Sources and spectral indices from the THOR survey.
Wang Y., Bihr S., Rugel M., Beuther H., Johnston K.G., Ott J., Soler J.D.,
Brunthaler A., Anderson L.D., Urquhart J.S., Klessen R.S., Linz H.,
McClure-Griffiths N.M., Glover S.C.O., Menten K.M., Bigiel F., Hoare M.,
Longmore S.N.
<Astron. Astrophys. 619, A124 (2018)>
=2018A&A...619A.124W 2018A&A...619A.124W (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Galactic plane ; Radio sources ; Radio continuum
Keywords: catalogs - surveys - radio continuum: general -
techniques: interferometric
Abstract:
Radio continuum surveys of the Galactic plane can find and
characterize HII regions, supernova remnants (SNRs), planetary nebulae
(PNe), and extragalactic sources. A number of surveys at high angular
resolution (≲25") at different wavelengths exist to study the
interstellar medium (ISM), but no comparable high-resolution and
high-sensitivity survey exists at long radio wavelengths around 21cm.
Our goal is to investigate the 21cm radio continuum emission in the
northern Galactic plane at <25" resolution.
We observed a large fraction of the Galactic plane in the first
quadrant of the Milky Way (l=14.0°-67.4° and |b|≤1.25°)
with the Karl G. Jansky Very Large Array (VLA) in the C-configuration
covering six continuum spectral windows. These data provide a detailed
view on the compact as well as extended radio emission of our Galaxy
and thousands of extragalactic background sources.
We used the BLOBCAT software and extracted 10916 sources. After
removing spurious source detections caused by the sidelobes of the
synthesised beam, we classified 10387 sources as reliable
detections.We smoothed the images to a common resolution of 25" and
extracted the peak flux density of each source in each spectral window
(SPW) to determine the spectral indices α (assuming
I(nu)∝nualpha). By cross-matching with catalogs of HII
regions, SNRs, PNe, and pulsars, we found radio counterparts for 840
HII regions, 52 SNRs, 164 PNe, and 38 pulsars. We found 79 continuum
sources that are associated with X-ray sources. We identified 699
ultrasteep spectral sources (alpha←1.3) that could be high-redshift
galaxies. Around 9000 of the sources we extracted are not classified
specifically, but based on their spatial and spectral distribution, a
large fraction of them is likely to be extragalactic background
sources. More than 7750 sources do not have counterparts in the SIMBAD
database, and more than 3760 sources do not have counterparts in the
NED database.
Studying the long wavelengths cm continuum emission and the associated
spectral indices allows us to characterize a large fraction of
Galactic and extragalactic radio sources in the area of the northern
inner Milky Way. This database will be extremely useful for future
studies of a diverse set of astrophysical objects.
Description:
We observed a part of the first quadrant of the Galactic plane
(l=14.0°-67.4° and |b|≤1.25°.) with the Karl G. Jansky
Very Large Array (VLA) in C configuration at L band from 1 to 2GHz.
The detailed observing strategy and data reduction is discussed and
described in Bihr et al. (2016A&A...588A..97B 2016A&A...588A..97B, Cat. J/A+A/588/A97) and
Beuther et al. (2016A&A...595A..32B 2016A&A...595A..32B). With the WIDAR correlator, we
cover the HI 21cm line, 4 OH lines, 19 Hα recombination lines,
as well as eight continuum bands, i.e., SPWs. Each continuum SPW has a
band width of 128MHz. Due to strong contamination from radio frequency
interference (RFI), two SPWs around 1.2 and 1.6GHz were not usable and
discarded. The remaining six SPWs are centered at 1.06, 1.31, 1.44,
1.69, 1.82 and 1.95GHz. For the fields at l=23.1°-24.3° and
25.6°-26.8., the SPW around 1.95GHz is also severely affected by
RFI and is therefore flagged (see Bihr et al., 2016A&A...588A..97B 2016A&A...588A..97B,
Cat. J/A+A/588/A97).
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
catalog.dat 733 10387 Full continuum catalog (corrected version from
erratum, A&A, 641, C1 (2020))
table4.dat 91 168 Fitting results for HII regions (corrected
version from erratum, A&A, 641, C1 (2020))
listavg.dat 150 42 List of fits files for average images
listcont.dat 194 250 List of continuum fits images
averaged_image/* . 42 Individual fits average images
cont_25arcsec/* . 250 Individual continuum fits images
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See also:
http://www2.mpia-hd.mpg.de/thor/DATA/www : THOR Data Access
Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 13 A13 --- Name Name of the source (GLL.lll+B.bbb) (Gal. ID)
15- 24 F10.6 deg RAdeg Right ascension (J2000) of
peak position (RA)
26- 35 F10.6 deg DEdeg Declination (J2000) of peak position (Dec)
37- 48 E12.7 Jy/beam Sp Peak intensity of the average image used for
source extraction (S_p) (1)
50- 61 E12.7 Jy Sint Integrated flux density of the averaged
image (S_int)
63- 70 F8.3 --- S/N Signal-to-noise ratio in the averaged
image (S/N)
72- 78 F7.4 arcsec BMAJ Major axis of the synthesized beam used for
source extraction (BMAJ)
80- 86 F7.4 arcsec BMIN Minor axis of the synthesized beam used for
source extraction (BMIN)
88- 96 F9.4 deg BPA Position angle of the synthesized beam used
for source extraction (BPA)
98-102 I5 --- Npix Number of pixels flooded by BLOBCAT (n_pix)
104 I1 --- Res [0/1] Resolved source label,
-1 = resolved, 0 = point
(resolved_source) (2)
106-127 E22.15 Jy/beam Sp1060 Peak intensity around 1.06GHz used for
spectral index (S_p(spw-1060)) (3)
129-150 E22.15 Jy/beam e_Sp1060 Uncertainty of peak intensity around
1.06GHz (deltaSp(spw-1060)) (3)
152-173 E22.15 Jy/beam Sp1310 Peak intensity around 1.31GHz used for
spectral index (S_p(spw-1310)) (3)
175-196 E22.15 Jy/beam e_Sp1310 Uncertainty of peak intensity around
1.31GHz (deltaSp(spw-1310)) (3)
198-219 E22.15 Jy/beam Sp1440 Peak intensity around 1.44GHz used for
spectral index (S_p(spw-1440)) (3)
221-242 E22.15 Jy/beam e_Sp1440 Uncertainty of peak intensity around
1.44GHz (deltaSp(spw-1440)) (3)
244-265 E22.15 Jy/beam Sp1690 Peak intensity around 1.69GHz used for
spectral index (S_p(spw-1690)) (3)
267-288 E22.15 Jy/beam e_Sp1690 Uncertainty of peak intensity around
1.69GHz (deltaSp(spw-1690)) (3)
290-311 E22.15 Jy/beam Sp1820 Peak intensity around 1.82GHz used for
spectral index (S_p(spw-1820)) (3)
313-334 E22.15 Jy/beam e_Sp1820 Uncertainty of peak intensity around
1.82GHz (deltaSp(spw-1820)) (3)
336-357 E22.15 Jy/beam Sp1950 ? Peak intensity around 1.95GHz used for
spectral index (S_p(spw-1950)) (3)
359-380 E22.15 Jy/beam e_Sp1950 ? Uncertainty of peak intensity around
1.95GHz (deltaSp(spw-1950)) (3)
382-393 F12.8 --- alpha ? Spectral index of source we derived
(alpha)
395-404 F10.8 --- e_alpha ? Uncertainty of spectral index
(delta_alpha)
406 I1 --- fitspws ? Number of SPWs used to fit the spectral
index (see Sect. ref§)
(fit_spws)
408-420 A13 --- Note Note (Note) (4)
422-724 A303 --- Ctp The counterparts of the HII region, SNR, the
planetary nebulae and the pulsars
(Counterparts)
726-727 I2 --- NCtp The total number of counterparts that the
continuum source is associated with
(Ncounter)
729-730 I2 --- GroupID ? The Group of continuum sources associated
with one or more same counterparts
(GroupID)
732-733 I2 --- GroupSize ? The number of the continuum sources in
the same group (GroupSize)
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Note (1): Synthesized beam is different for different fields.
Note (2): Resolved source label as follows:
1 = resolved
0 = point
Note (3): Synthesized beam is smoothed to 25"x25".
spw-1060 = Frequency range: 989-1117MHz
spw-1310 = Frequency range: 1244-1372MHz
spw-1440 = Frequency range: 1372-1500MHz
spw-1690 = Frequency range: 1628-1756MHz
spw-1820 = Frequency range: 1756-1884MHz
spw-1950 = Frequency range: 1884-2012MHz
Note (4): We classified the continuum source as follows:
HII = sources associated with HII regions from
Anderson et al. (2014, Cat. J/ApJS/212/1)
SNR_green = sources associated with SNRs from Green (2014, Cat. VII/272)
SNR_anderson = sources associated with SNR candidates from
Anderson et al. (2017A&A...605A..58A 2017A&A...605A..58A)
PN = sources classified as planetary nebula
PSR = sources classified as pulsars
Xray = sources associated with X-ray sources
jets = sources classified as extragalactic jets candidates
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 13 A13 --- Name Name of the source (GLL.lll+B.bbb) (Gal.ID)
15- 25 F11.8 --- alpha Spectral index of source we derived (alpha)
27- 36 F10.8 --- e_alpha Uncertainty of spectral index (delta_alpha)
38- 57 A20 --- HIIname Name of the HII regions (GLLL.lll+BB.bbb,
HRDS GLLL.lll+BB.bbb in Simbad) (HII name)
59- 62 I4 K Te ?=0 Electron temperature (T_e) (1)
64- 70 F7.4 kpc d ?=0 Distance from the WISE catalog (d)
72- 82 F11.4 pc/cm6 EM Emission measure (EM)
84- 91 F8.4 cm-3 Ne ?=0 Electron density (Ne) (2)
--------------------------------------------------------------------------------
Note (1): Te is assumed to be 8000K if it is not available from the WISE
catalog.
Note (2): Ne is calculated if distance is available from the WISE catalog.
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Byte-by-byte Description of file: listavg.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 A1 --- G [G]
2- 10 F9.5 deg GLON Galactic longitude of center (J2000)
11- 19 F9.5 deg GLAT Galactic latitude center (J2000)
21- 24 I4 --- Nx Number of pixels along X-axis
26- 29 I4 --- Ny Number of pixels along Y-axis
31- 56 A26 --- Obs.date Observation date (YYYY-MM-DDThh:mm:ss.ssssss)
58- 62 I5 Kibyte size Size of FITS file
64-100 A37 --- FileName Name of FITS file,
in subdirectory averaged_image
102-150 A49 --- Title Title of the FITS file
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Byte-by-byte Description of file: listcont.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 A1 --- G [G]
2- 10 F9.5 deg GLON Galactic longitude of center (J2000)
11- 19 F9.5 deg GLAT Galactic latitude center (J2000)
21- 24 I4 --- Nx Number of pixels along X-axis
26- 29 I4 --- Ny Number of pixels along Y-axis
31- 56 A26 --- Obs.date Observation date (YYYY-MM-DDThh:mm:ss.ssssss)
58- 69 E12.6 m/s VRAD ? Radial velocity
71- 75 I5 Kibyte size Size of FITS file
77-123 A47 --- FileName Name of FITS file,
in subdirectory cont_25arcsec
125-194 A70 --- Title Title of the FITS file
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Acknowledgements:
Yuan Wang, wang(at)mpia.de
History:
14-Nov-2018: on-line version
30-Jun-2020: Corrected version of table 4 and catalog
(from erratum, A&A, 641, C1 (2020))
(End) Patricia Vannier [CDS] 30-Aug-2018