J/ApJ/959/110 GBT Diffuse Ionized Gas Survey (GDIGS) RRL data (Linville+, 2023)
The GBT Diffuse Ionized Gas Survey (GDIGS): discrete sources.
Linville D.J., Luisi M., Anderson L.D., Liu B., Bania T.M., Balser D.S.,
Wenger T.V., Haffner L.M., Mascoop J.L.
<Astrophys. J., 959, 110 (2023)>
=2023ApJ...959..110L 2023ApJ...959..110L
ADC_Keywords: Milky Way; Interstellar medium; H II regions; Space velocities;
Surveys; Galactic plane; Radio lines; Infrared sources
Keywords: Warm ionized medium ; Interstellar plasma ; H II regions ;
Interstellar line emission ; Interstellar medium
Abstract:
The Green Bank Telescope Diffuse Ionized Gas Survey (GDIGS) traces
ionized gas in the Galactic midplane by observing radio recombination
line (RRL) emission from 4 to 8GHz. The nominal survey zone is
32.3°>l>-5°, |b|<0.5°. Here, we analyze GDIGS Hnα
ionized gas emission toward discrete sources. Using GDIGS data, we
identify the velocity of 35 HII regions that have multiple detected
RRL velocity components. We identify and characterize RRL emission
from 88 HII regions that previously lacked measured ionized gas
velocities. We also identify and characterize RRL emission from eight
locations that appear to be previously unidentified HII regions and
30 locations of RRL emission that do not appear to be HII regions
based on their lack of mid-infrared emission. This latter group may be
a compact component of the Galactic Diffuse Ionized Gas. There are an
additional 10 discrete sources that have anomalously high RRL
velocities for their locations in the Galactic plane. We compare these
objects' RRL data to 13CO, HI, and mid-infrared data, and find that
these sources do not have the expected 24µm emission characteristic
of HII regions. Based on this comparison we do not think these objects
are HII regions, but we are unable to classify them as a known type of
object.
Description:
The Green Bank Telescope Diffuse Ionized Gas Survey (GDIGS) is a
survey of ionized gas in the midplane of the Milky Way. The GDIGS
radio recombination line (RRL) data were first published in
Anderson+ (2021ApJS..254...28A 2021ApJS..254...28A).
The GDIGS data were collected using the C-band receiver on the Green
Bank Telescope (GBT) in total power mode. Within the 4-8GHz bandpass,
we tuned to 15 usable hydrogen RRLs, as defined in Anderson+ (2021).
We also use 3.6 and 8.0um data from the Spitzer GLIMPSE survey
(see II/293) and 24um data from the MIPSGAL survey
(Carey+ 2009PASP..121...76C 2009PASP..121...76C). See Section 2.2.
We compare the regions discussed in this paper to those of the "WISE
Catalog" (Anderson+ 2014, J/ApJS/212/1). See Section 2.3.
We detect RRL emission for 40 "group" HII regions, 27 HII region
candidates, and 21 radio-quiet HII regions, all from the WISE catalog.
In total, we move 89 WISE Catalog objects into the "known" HII region
category.
We detect RRL emission from eight locations that we believe to be
previously unknown Galactic HII regions.
We detect 30 GDIGS discrete sources that lack coincident MIR emission,
and therefore we conclude they are not HII regions. We detect and
characterize via Gaussian fitting the RRL emission from these
locations; see Table 6.
Finally, we identify 10 locations of anomalously high-velocity RRL
emission, which we refer to as AVFs which are likely not HII regions.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 73 58 GDIGS Hnα RRL parameters from
WISE catalog group HII regions
table3.dat 73 37 GDIGS Hnα RRL parameters from
WISE catalog candidate HII regions
table4.dat 73 27 GDIGS Hnα RRL parameters from
WISE catalog radio-quiet HII regions
table5.dat 77 13 GDIGS Hnα RRL parameters from
new HII regions
table6.dat 77 43 GDIGS Hnα RRL parameters from
discrete emission zones (DEZs)
table7.dat 77 10 Anomalous velocity features (AVFs)
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See also:
VIII/58 : A Survey of Radio H II Regions in the Northern Sky (Lockman+ 1989)
II/249 : WHAM Northern Sky Survey, V-1.1 (Haffner+, 2003)
II/293 : GLIMPSE Source Catalog (I + II + 3D) (IPAC 2008)
II/311 : WISE All-Sky Data Release (Cutri+ 2012)
J/ApJ/690/706 : Distances of Galactic HII regions (Anderson+, 2009)
J/ApJS/181/255 : CO in Galactic HII regions (Anderson+, 2009)
J/ApJS/194/32 : HII Region Discovery Survey (HRDS). II. (Anderson+, 2011)
J/A+A/537/A1 : Infrared fluxes of HII regions and PNe (Anderson+, 2012)
J/ApJS/212/1 : The WISE catalog of Galactic HII regions (Anderson+, 2014)
J/MNRAS/450/2025 : HIPASS-ZoA HII regions (Alves+, 2015)
J/AJ/149/64 : MIPSGAL 24µm point source catalog (Gutermuth+, 2015)
J/ApJ/810/42 : Hydrogen RRL parameters of H II regions (Anderson+, 2015)
J/ApJ/841/121 : HII region cand. in the OSC spiral arm (Armentrout+, 2017)
J/ApJ/839/113 : Molecular clouds with GLIMPSE/MIPSGAL (Retes-Romero+, 2017)
J/ApJS/234/33 : A GBT survey of large Galactic HII regions (Anderson+, 2018)
J/ApJS/240/14 : SIGGMA: inner galaxy data release (Liu+, 2019)
J/ApJ/885/131 : High-mass SFR plx & proper motion with VLBI (Reid+, 2019)
J/MNRAS/500/3064 : The SEDIGISM survey: First Data Release (Schuller+, 2021)
J/ApJS/254/36 : Southern HII Region Discovery Survey. II. (Wenger+, 2021)
Byte-by-byte Description of file: table[2-7].dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- Name Source identifier (GLLL.lll+BB.bbb)
16 A1 --- f_Name Flag on Name (1)
18- 24 F7.3 deg GLON [0.1/360] Galactic longitude
26- 31 F6.3 deg GLAT [-0.9/1.2] Galactic latitude
33- 37 F5.1 mK TL [2.6/464.2] Line intensity, TL
39- 41 F3.1 mK e_TL [0.1/2.5] TL 1σ uncertainty
43- 48 F6.1 km/s VLSR [-214/228] Local Standard of Rest velocity
50- 52 F3.1 km/s e_VLSR [0.1/6.2] VLSR 1σ uncertainty
54- 57 F4.1 km/s DelV [5/81.1] The FWHM line width, ΔV
59- 62 F4.1 km/s e_DelV [0.1/15.6] DelV 1σ uncertainty
64- 67 F4.1 --- rms [0.9/12.4] rms noise
69- 73 F5.1 --- S/N [3.5/410.5] Signal-to-noise ratio
75- 77 I3 arcsec Rad [105/752]? Region radius;
not for the "WISE catalog" (Tables 2, 3 and 4)
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Note (1): For sources with multiple RRL velocity components, we apply the
method described in Section 3.1.1. If the correct velocity can be
determined, we report the correct velocity first, followed by the
other velocity with an asterisk appended to the name. For sources for
which we cannot determine which velocity is correct, we report both,
appended with "a" and "b" in order of decreasing Hnα intensity.
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Nomenclature Notes:
For the "WISE catalog" (Anderson+ 2014, J/ApJS/212/1; Tables 2-4),
the sources are <[ABB2014] WISE GLLL.lll+BB.bbb> in Simbad.
History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 29-Jan-2026