J/ApJ/887/114 VLA ∼8-10GHz obs. of WISE Galactic HII regions (Wenger+, 2019)
Metallicity structure in the Milky Way disk revealed by Galactic HII regions.
Wenger T.V., Balser D.S., Anderson L.D., Bania T.M.
<Astrophys. J., 887, 114-114 (2019)>
=2019ApJ...887..114W 2019ApJ...887..114W (SIMBAD/NED BibCode)
ADC_Keywords: H II regions; Milky Way; Interstellar medium; Radio continuum;
Surveys; Space velocities; Infrared sources
Keywords: Milky Way Galaxy; Interstellar medium; Nebulae; Surveys
Abstract:
The metallicity structure of the Milky Way disk stems from the
chemodynamical evolutionary history of the Galaxy. We use the National
Radio Astronomy Observatory Karl G. Jansky Very Large Array to observe
∼8-10GHz hydrogen radio recombination line and radio-continuum
emission toward 82 Galactic HII regions. We use these data to derive
the electron temperatures and metallicities for these nebulae. Since
collisionally excited lines from metals (e.g., oxygen, nitrogen) are
the dominant cooling mechanism in HII regions, the nebular metallicity
can be inferred from the electron temperature. Including previous
single-dish studies, there are now 167 nebulae with radio-determined
electron temperature and either parallax or kinematic distance
determinations. The interferometric electron temperatures are
systematically 10% larger than those found in previous single-dish
studies, likely due to incorrect data analysis strategies, optical
depth effects, and/or the observation of different gas by the
interferometer. By combining the interferometer and single-dish
samples, we find an oxygen abundance gradient across the Milky Way
disk with a slope of -0.052±0.004dex/kpc. We also find significant
azimuthal structure in the metallicity distribution. The slope of the
oxygen gradient varies by a factor of ∼2 when Galactocentric azimuths
near ∼30° are compared with those near ∼100°. This azimuthal
structure is consistent with simulations of Galactic chemodynamical
evolution influenced by spiral arms.
Description:
We used the Karl G. Jansky Very Large Array (VLA) to simultaneously
observe radio-continuum and RRL emission toward our sample of
147 Galactic HII regions. The data were acquired in the most compact
(D) antenna configuration as part of two projects: the pilot survey
(13A-030; 5hr) in Feb and Apr 2013, and the main survey (15B-178; 30hr)
in Oct and Nov 2015. The VLA X-band receiver covers the frequency
range ∼8-12GHz.
The continuum data were measured by 16 low spectral resolution
spectral windows covering 7.8-8.9GHz and 9-10GHz continuously. The
radio recombination line (RRL) spectra were measured by eight
high-spectral resolution (31.25kHz) spectral windows, each with 16MHz
of frequency coverage. See Section 3.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 115 148 Survey targets
table4.dat 61 114 Continuum data products
table5.dat 103 82 Radio recombination line (RRL) data products
table6.dat 110 189 HII region distances and properties
refs.dat 65 39 References
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See also:
VIII/58 : A Survey of Radio H II Regions in the Northern Sky (Lockman+ 1989)
J/ApJS/165/338 : Radio recombination lines in HII regions (Quireza+, 2006)
J/AJ/132/902 : Abundances of 54 Cepheids (Luck+, 2006)
J/ApJ/653/1226 : Physical properties of galactic HII regions (Quireza+, 2006)
J/ApJ/699/1153 : Kinematic dist. to GRS molecular clouds (Roman-Duval+, 2009)
J/ApJ/720/1055 : VBLA observations of W51 Main/South (Sato+, 2010)
J/ApJS/194/32 : The HII Region Discovery Survey (HRDS). II. (Anderson+, 2011)
J/ApJ/738/27 : Galactic HII regions RRL and continuum data (Balser+, 2011)
J/MNRAS/420/1656 : RMS compact HII regions distances (Urquhart+, 2012)
J/ApJ/754/62 : HRDS III. HII region kinematic distances (Anderson+, 2012)
J/ApJ/783/130 : Parallaxes of high mass star forming regions (Reid+, 2014)
J/ApJS/212/1 : The WISE catalog of Galactic HII regions (Anderson+, 2014)
J/MNRAS/444/3301 : Oxygen abundance in Galactic disc Cepheids (Korotin+, 2014)
J/ApJ/806/199 : RRL & continuum data of 21 Gal. H II regions (Balser+, 2015)
J/ApJ/810/42 : Hydrogen RRL parameters of H II regions (Anderson+, 2015)
J/ApJS/221/26 : Radio observations of Gal. WISE HII regions (Anderson+, 2015)
J/A+A/587/A70 : CALIFA face-on spiral gal. oxygen (Sanchez-Menguiano+, 2016)
J/A+A/588/A97 : Continuum sources from the THOR survey (Bihr+, 2016)
J/A+A/597/A30 : Seismology & spectrosc. of CoRoGEE red giants (Anders+, 2017)
J/ApJS/234/33 : A GBT survey of large Galactic HII regions (Anderson+, 2018)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- Name Field identifier (GLLL.lll+BB.bbb) (G1)
17- 23 A7 --- PID The VLA project in which the HII region was
observed (13A-030 is the pilot survey
and 15B-178 is the main survey)
25- 26 I2 h RAh WISE IR hour of right ascension (J2000)
28- 29 I2 min RAm WISE IR minute of right ascension (J2000)
31- 34 F4.1 s RAs WISE IR second of right ascension (J2000)
36 A1 --- DE- WISE IR sign of declination (J2000)
37- 38 I2 deg DEd WISE IR degree of declination (J2000)
40- 41 I2 arcmin DEm WISE IR arcminute of declination (J2000)
43- 46 F4.1 arcsec DEs WISE IR arcsecond of declination (J2000)
48- 54 F7.2 arcsec RadIR [21/1541] The WISE infrared radius, RIR
56- 62 F7.2 mJy/beam S9GHz [2/3357] The estimated 9GHz RRL flux density
64- 68 F5.2 mJy/beam e_S9GHz [0.04/27] S9GHz uncertainty
70- 77 A8 --- Tel Original RRL detection telescope
79- 82 A4 --- Ref Reference for the original RRL detection
(see refs.dat file)
84- 89 F6.4 --- SL/SC [0.0423/0.1817]? The previously measured
RRL-to-continuum brightness ratio, SL/SC
91- 96 F6.4 --- e_SL/SC [0.0003/0.007]? SL/SC uncertainty
98-102 I5 K Te [5335/14578]? The derived electron
temperature
104-106 I3 K e_Te [47/462]? Te uncertainty
108-115 A8 --- r_Te Reference for the RRL-to-continuum brightness
ratio and electron temperature
(see refs.dat file)
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- Name Name of the HII region (GLLL.lll+BB.bbb) (G1)
17- 22 F6.1 MHz Vc [8898/8964.1] the MS-MFS synthesized frequency
of the combined continuum spectral windows
24- 30 F7.2 mJy/beam ScP [1/7191.1] the peak continuum flux density,
SCP
32- 37 F6.2 mJy/beam e_ScP [0.02/150] ScP uncertainty
39 A1 --- QFcP Quality factor for the peak flux density (1)
41 A1 --- TapP the peak flux density was measured using the
non-tapered ("N") or uv-tapered ("Y") image
43- 50 F8.2 mJy ScT [0.04/11723] the total flux density within the
watershed region, SCT
52- 57 F6.2 mJy e_ScT [0.07/399] ScT uncertainty
59 A1 --- QFcT Quality factor for the total flux density (1)
61 A1 --- TapT The total flux density was measured using the
non-tapered ("N") or uv-tapered ("Y") image
--------------------------------------------------------------------------------
Note (1): The quality factor (QF) is a qualitative assessment of the accuracy
of the continuum flux measurement as follows:
A = detections are isolated, unresolved, and near the center of the
primary beam
B = detections are slightly resolved, in crowded fields, and/or are located
off center from the primary beam
C = detections are well-resolved, in very crowded fields, and/or are located
near the edge of the primary beam
See Section 5.1.
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Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- Name Name of the HII region (GLLL.lll+BB.bbb) (G1)
17- 22 F6.1 MHz Vl [8542.6/8974.4] The weighted average
frequency of the <Hnα> spectrum (1)
24- 30 F7.2 mJy/beam SlP [1.7/1098]? Amplitude of the Gaussian fit to
the spectrum extracted from the location of
peak continuum brightness, SLP
32- 35 F4.2 mJy/beam e_SlP [0.2/3.1]? SlP uncertainty
37- 41 F5.2 mJy/beam rmsP [0.6/11.8]? The spectral rms at this position
43- 47 F5.1 km/s VlsrP [-87.5/100.4]? Center LSR velocity of the
fitted Gaussian
49- 51 F3.1 km/s e_VlsrP [0/2.2]? VlsrP uncertainty
53- 56 F4.1 km/s delVP [12/39]? FWHM line width of the fitted
Gaussian, ΔVP
58- 60 F3.1 km/s e_delVP [0.1/7]? delVP uncertainty
62 A1 --- TapP The spectrum was extracted from the
non-tapered ("N") or uv-tapered ("Y") image
64- 70 F7.2 mJy SlT [1.7/2080]? Amplitude of the Gaussian fit to
the spectrum summed within the watershed
region
72- 75 F4.2 mJy e_SlT [0.03/6]? SlT uncertainty
77- 81 F5.2 mJy rmsT [0.1/22.1]? The spectral rms in this region
83- 87 F5.1 km/s VlsrT [-97.7/101]? Center LSR velocity of the
fitted Gaussian
89- 91 F3.1 km/s e_VlsrT [0/4.5]? VlsrT uncertainty
93- 96 F4.1 km/s delVT [13.5/40]? FWHM line width of the fitted
Gaussian
98- 101 F4.1 km/s e_delVT [0.1/22]? delVT uncertainty
103 A1 --- TapT He spectrum was extracted from the
non-tapered ("N") or uv-tapered ("Y") image
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Note (1): The weighted average frequency of the <Hnα> spectrum, νL,
where the weights are the same as those used to average the individual
RRL transitions (see Section 4).
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Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- Name Name of the HII region (GLLL.lll+BB.bbb) (G1)
17- 24 A8 --- Tel Telescope used for the observation
26- 31 F6.4 --- SL/SC [0.04/0.3] Measured RRL-to-continuum flux ratio
33- 38 F6.4 --- e_SL/SC [0.0002/0.04] SL/SC uncertainty
40- 43 F4.1 km/s delV [13.5/42] RRL FWHM line width
45- 47 F3.1 km/s e_delV [0/5.6] delV uncertainty
49- 53 I5 K Te [4061/14189] Derived electron temperature
55- 58 I4 K e_Te [19/2932] Te uncertainty
60 A1 --- Type Source type (1)
62 A1 --- Tap Taper column identifying which data cube is used
("N" for non-tapered and "Y" for uv-tapered)
64- 68 F5.2 kpc Dist [0.09/19.5]? HII region distance
(see Section 5.4)
70- 73 F4.2 kpc e_Dist [0/1.47]? Lower uncertainty on Dist
75- 78 F4.2 kpc E_Dist ? Upper uncertainty on Dist
79 A1 --- f_Dist Flag on Dist (2)
81- 85 F5.2 kpc Rad [0.2/15.2]? Radius
87- 90 F4.2 kpc e_Rad [0/1.31]? Lower uncertainty on Rad
92- 95 F4.2 kpc E_Rad ? Upper uncertainty on Rad
96 A1 --- f_Rad Flag on Rad (2)
98 A1 --- Meth Distance method (3)
100- 110 A11 --- r_Dist Reference on Dist (see refs.dat file)
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Note (1): VLA source type as follows:
P = measured at the location of peak continuum brightness;
T = measured within the watershed segmentation region
Note (2): Flag as follows:
d = Kinematic distances are unreliable in the direction of the Galactic
center and anti-center.
Note (3): Distance method as follows:
K = Monte Carlo kinematic distance;
P = parallax distance
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Byte-by-byte Description of file: refs.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- Ref Reference code
6- 24 A19 --- BibCode Bibcode of the reference
26- 43 A18 --- Auth First author's name
45- 65 A21 --- Comm VizieR catalog designation
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Global notes:
Note (G1): the WISE Catalog (Anderson+ 2014, J/ApJS/212/1) source name;
<[ABB2014] WISE GLLL.lll+BB.bbb> in Simbad
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 01-Mar-2023