J/ApJ/901/51 Radio continuum param. of Galactic HII regions (Anderson+, 2020)
Unusual Galactic HII regions at the intersection of the central molecular zone
and the far dust lane.
Anderson L.D., Sormani M.C., Ginsburg A., Glover S.C.O., Heywood I.,
Rammala I., Schuller F., Csengeri T., Urquhart J.S., Bronfman L.
<Astrophys. J., 901, 51 (2020)>
=2020ApJ...901...51A 2020ApJ...901...51A
ADC_Keywords: H II regions; Galactic center; Interstellar medium;
Radio continuum
Keywords: H II regions ; Galactic center ; Interstellar medium ;
Radio continuum emission
Abstract:
Sgr E is a massive star formation complex found toward the Galactic
center that consists of numerous discrete, compact HII regions. It is
located at the intersection between the central molecular zone (CMZ)
and the far dust lane of the Galactic bar, similar to "hot spots" seen
in external galaxies. Compared with other Galactic star formation
complexes, the Sgr E complex is unusual because its HII regions all
have similar radio luminosities and angular extents, and they are
deficient in ∼10µm emission from their photodissociation regions
(PDRs). Our Green Bank Telescope radio recombination line observations
increase the known membership of Sgr E to 19 HII regions. There are
43 additional HII region candidates in the direction of Sgr E, 26 of
which are detected for the first time here using MeerKAT 1.28GHz data.
Therefore, the true HII region population of Sgr E may number >60.
Using APEX SEDIGISM 13CO 2->1 data we discover a 3.0x105M☉
molecular cloud associated with Sgr E, but find few molecular or
far-infrared concentrations at the locations of the Sgr E HII regions.
Comparison with simulations and an analysis of its radio continuum
properties indicate that Sgr E formed upstream in the far dust lane of
the Galactic bar a few million years ago and will overshoot the CMZ,
crashing into the near dust lane. We propose that the unusual infrared
properties of the Sgr E HII regions are caused by their orbits about
the Galactic center, which have possibly stripped their PDRs.
Description:
We observe radio recombination line (RRL) emission using the Green
Bank Telescope (GBT) from three WISE HII region candidates
(Anderson+, 2014, J/ApJS/212/1) in order to determine whether they
belong to SgrE. HII regions in the SgrE complex will have velocities
near -200km/s. These three sources are the WISE Catalog HII region
candidates in the SgrE field that have the brightest radio continuum
emission, as assessed by NVSS 1.4GHz data.
The Sgr E region was observed by MeerKAT as part of its
commissioning-phase survey of the Galactic center region. The pointing
relevant to this work was observed on 2018 June 23, centered at
RAJ2000=17:41:36.530,DEJ2000=30:09:56.39. The MeerKAT telescope is
operated by the South African Radio Astronomy Observatory.
See Section 2.3.
To investigate dense gas in the region, we use the Green Bank
Telescope to observe the (1,1) through (5,5) transitions of NH3
(from 23.6945 to 24.5330GHz) as well as the H2O maser transition
6(1,6)->5(2,3) (at 22.2351GHz) and the N=1->2,J=2->1 transition of CCS
(at 22.3440GHz). See Section 2.7.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 71 19 SgrE HII region radio continuum parameters
table3.dat 56 40 Candidate SgrE HII region radio continuum parameters
table4.dat 75 326 NH3 line parameters
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See also:
VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
J/ApJS/175/509 : Ammonia spectral atlas in Perseus (Rosolowsky+, 2008)
J/ApJ/690/706 : Distances of Galactic HII regions (Anderson+, 2009)
J/ApJS/181/255 : CO in Galactic HII regions (Anderson+, 2009)
J/ApJ/709/424 : HII regions identified with WMAPS & GLIMPSE (Murray+, 2010)
J/ApJS/194/32 : HII Region Discovery Survey (HRDS). II. (Anderson+, 2011)
J/ApJ/738/27 : Galactic HII regions RRL and continuum data (Balser+, 2011)
J/MNRAS/418/1689 : Red MSX water maser and ammonia emissions (Urquhart+, 2011)
J/ApJ/754/62 : HRDS III. HII region kinematic distances (Anderson+, 2012)
J/A+A/537/A1 : Infrared fluxes of HII regions and PNe (Anderson+, 2012)
J/A+A/537/A146 : Stellar models with rotation; 0.8<M<120 (Ekstrom+, 2012)
J/ApJS/208/11 : Red MSX Source Survey: massive protostars (Lumsden+, 2013)
J/ApJS/212/1 : The WISE catalog of Galactic HII regions (Anderson+, 2014)
J/ApJS/221/26 : Radio obs. of Galactic WISE HII regions (Anderson+, 2015)
J/A+A/586/A50 : CMZ H2CO temperature maps (Ginsburg+, 2016)
J/ApJ/834/57 : MW molecular clouds from 12CO (Miville-Deschenes+, 2017)
J/A+A/601/A124 : Clouds in SEDIGISM field (Schuller+, 2017)
J/A+A/624/A63 : W51 OB stars NIR spectroscopy (Bik+, 2019)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- Name Name (GLLL.lll+BB.bbb;
<[ABB2014] WISE GLLL.lll+BB.bbb> in Simbad)
17- 18 I2 h RAh [17] Hour of Right Ascension (J2000)
20- 21 I2 min RAm [41/43] Minute of Right Ascension (J2000)
23- 26 F4.1 s RAs Second of Right Ascension (J2000)
28- 28 A1 --- DE- [-] Sign of the Declination (J2000)
29- 30 I2 deg DEd [29/30] Degree of Declination (J2000)
32- 33 I2 arcmin DEm Arcminute of Declination (J2000)
35- 36 I2 arcsec DEs Arcsecond of Declination (J2000)
38- 43 F6.1 km/s VLSR1 [-217/-182.2] Velocity relative to local
standard of rest (LSR)
45- 50 F6.1 km/s VLSR2 [-215.6/-5.4]? Other velocity component
relative to LSR
52- 54 F3.1 pc Diam [0.7/7.4] Diameter
56- 60 F5.1 mJy F1.28 [4.4/576.7] MeerKAT flux density at 1.28GHz
62- 66 F5.2 [ph/s] logNly [46.47/48.58] log of Lyman continuum luminosity
68- 71 A4 --- SpT Spectral type
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- Name Name (GLLL.lll+BB.bbb;
<[ABB2014] WISE GLLL.lll+BB.bbb> in Simbad)
17- 18 I2 h RAh [17] Hour of Right Ascension (J2000)
20- 21 I2 min RAm [41/43] Minute of Right Ascension (J2000)
23- 26 F4.1 s RAs Second of Right Ascension (J2000)
28- 28 A1 --- DE- [-] Sign of the Declination (J2000)
29- 30 I2 deg DEd [29/30] Degree of Declination (J2000)
32- 33 I2 arcmin DEm Arcminute of Declination (J2000)
35- 36 I2 arcsec DEs Arcsecond of Declination (J2000)
38- 40 F3.1 pc Diam [0.6/4.1] Diameter
42- 45 F4.1 mJy F1.28 [0.3/42.4] MeerKAT flux density at 1.28GHz
47- 51 F5.2 [ph/s] logNly [45.24/47.44] log of Lyman continuum luminosity
53- 56 A4 --- SpT Spectral type
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- Name Name, there are multiple positions
per HII region
17- 18 I2 h RAh [17] Hour of Right Ascension (J2000)
20- 21 I2 min RAm [41/43] Minute of Right Ascension (J2000)
23- 27 F5.2 s RAs Second of Right Ascension (J2000)
29- 29 A1 --- DE- [-] Sign of the Declination (J2000)
30- 31 I2 deg DEd [29/30] Degree of Declination (J2000)
33- 34 I2 arcmin DEm Arcminute of Declination (J2000)
36- 39 F4.1 arcsec DEs Arcsecond of Declination (J2000)
41- 45 A5 --- Line NH3 component
47- 51 F5.1 mK Tmb [19.5/290.4]? Main beam brightness temperature
53- 55 F3.1 mK e_Tmb [0.5/4]? Uncertainty in Tmb
57- 62 F6.1 km/s VLSR [-243.4/19.6]? Velocity relative to
local standard of rest
64- 66 F3.1 km/s e_VLSR [0.1/0.2]? Uncertainty in VLSR
68- 71 F4.1 km/s dV [1.3/40.3]? Linewidth
73- 75 F3.1 km/s e_dV [0.1/0.9]? Uncertainty in dV
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 05-Jan-2022