J/ApJS/234/24 VLA 33GHz obs. of star-forming regions (Murphy+, 2018)
The Star Formation in Radio Survey: Jansky Very Large Array 33GHz observations
of nearby galaxy nuclei and extranuclear star-forming regions.
Murphy E.J., Dong D., Momjian E., Linden S., Kennicutt R.C., Meier D.S.,
Schinnerer E., Turner J.L.
<Astrophys. J. Suppl. Ser., 234, 24 (2018)>
=2018ApJS..234...24M 2018ApJS..234...24M
ADC_Keywords: Galaxies, IR ; Radio continuum ; Interferometry ;
Photometry, H-alpha ; Active gal. nuclei ; Star Forming Region
Keywords: galaxies: nuclei; H II regions; radio continuum: general;
stars: formation
Abstract:
We present 33GHz imaging for 112 pointings toward galaxy nuclei and
extranuclear star-forming regions at ∼2" resolution using the Karl G.
Jansky Very Large Array (VLA) as part of the Star Formation in Radio
Survey. A comparison with 33GHz Robert C. Byrd Green Bank Telescope
single-dish observations indicates that the interferometric VLA
observations recover 78%±4% of the total flux density over 25"
regions (∼kpc scales) among all fields. On these scales, the emission
being resolved out is most likely diffuse non-thermal synchrotron
emission. Consequently, on the ∼30-300pc scales sampled by our VLA
observations, the bulk of the 33GHz emission is recovered and
primarily powered by free-free emission from discrete HII regions,
making it an excellent tracer of massive star formation. Of the 225
discrete regions used for aperture photometry, 162 are extranuclear
(i.e., having galactocentric radii rG≥250pc) and detected at
>3σ significance at 33GHz and in Hα. Assuming a typical
33GHz thermal fraction of 90%, the ratio of optically-thin 33GHz to
uncorrected Hα star formation rates indicates a median
extinction value on ∼30-300pc scales of AHα∼1.26±0.09mag,
with an associated median absolute deviation of 0.87mag. We find that
10% of these sources are "highly embedded" (i.e., AHα≳3.3mag),
suggesting that on average, HII regions remain embedded for ≲1Myr.
Finally, we find the median 33GHz continuum-to-Hα line flux
ratio to be statistically larger within rG<250pc relative to the outer
disk regions by a factor of 1.82±0.39, while the ratio of 33GHz to
24µm flux densities is lower by a factor of 0.45±0.08, which may
suggest increased extinction in the central regions.
Description:
The Star Formation in Radio Survey (SFRS) sample comprises nuclear and
extranuclear star-forming regions in 56 nearby galaxies (d<30Mpc)
observed as part of the SINGS (Kennicutt+ 2003PASP..115..928K 2003PASP..115..928K) and
KINGFISH (Kennicutt+ 2011PASP..123.1347K 2011PASP..123.1347K) legacy programs.
See section 2.1 for further explanations.
Observations in the Ka-band (26.5-40GHz) were taken during two
separate VLA D-configuration cycles. D-configuration observations were
obtained in 2011 November (VLA/11B-032) and 2013 March (VLA/13A-129).
See sections 2.2 and 2.3 for further details.
The Hα imaging used in the analysis is taken from references
cited in the compilation by Leroy+ (2012AJ....144....3L 2012AJ....144....3L), where
details about the data quality and preparation (e.g., correction for
[NII] emission) can be found. Hα images were corrected for
foreground stars. See sections 2.4 and 2.5.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 71 50 Galaxy properties and nuclear source positions
table2.dat 35 62 Extranuclear source positions
table5.dat 74 225 Source photometry (full resolution)
table6.dat 89 179 *Source photometry at 7" resolution
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Note on table6.dat: To accurately match the photometry obtained with the 33GHz
and Hα images to that measured using the Spitzer 24um data, which is at
much lower resolution (∼7"), we first resolution-matched the images. Both the
33GHz and Hα images were convolved with a Gaussian kernel resulting in
a final FWHM of 7". See section 2.6 for further explanations.
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See also:
J/ApJS/112/315 : Spectroscopic parameters of Seyfert nuclei (Ho+ 1997)
J/ApJ/559/864 : Extragalactic ultracompact H II regions (Johnson+, 2001)
J/ApJ/577/31 : PNe in six galaxies (Ciardullo+, 2002)
J/ApJ/703/517 : The Spitzer Local Volume Legacy: IR photometry (Dale+, 2009)
J/ApJS/190/233 : Spectroscopy & abundances of SINGS galaxies (Moustakas+, 2010)
J/ApJ/761/97 : Star Formation in Radio Survey (SFRS): 33GHz (Murphy+, 2012)
J/A+A/576/A33 : KINGFISH galaxy sample radial profile SED (Hunt+, 2015)
J/ApJ/836/185 : Radio continuum SEDs from KINGFISHER (Tabatabaei+, 2017)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Name Galaxy name
12- 13 I2 h RAh Hour of right ascension (J2000)
15- 16 I2 min RAm Minute of right ascension (J2000)
18- 21 F4.1 s RAs Second of right ascension (J2000)
23 A1 --- DE- Sign of declination (J2000)
24- 25 I2 deg DEd Degree of declination (J2000)
27- 28 I2 arcmin DEm Arcminute of declination (J2000)
30- 31 I2 arcsec DEs Arcsecond of declination (J2000)
33- 38 A6 --- Type Morphological type (1)
40- 44 F5.2 Mpc Dist [3/30.6] Redshift-independent distance (2)
46- 51 A6 --- NucType Nuclear type based on optical spectroscopy (3)
52 A1 --- f_NucType [*] *: nuclear type taken in table 4 of
Ho+ (1997, J/ApJS/112/315)
54- 57 F4.1 arcmin D25a [1/29] Diameter (major axis) D25 (1)
58 A1 --- --- [x]
59- 62 F4.1 arcmin D25b [0.9/26] Diameter (minor axis) D25 (1)
64- 65 I2 deg Inc [21/83] Inclination
67- 69 I3 deg PA [10/173] Positions angle (1)
71 A1 --- f_PA [d] d: PA taken from
Jarrett+ (2003AJ....125..525J 2003AJ....125..525J)
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Note (1): Morphological types, diameters, and position angles were taken from
the Third Reference Catalog of Bright Galaxies (RC3;
de Vaucouleurs et al. 1991, VII/155).
Note (2): Redshift-independent distance taken from the list compiled by
Kennicutt+ (2011PASP..123.1347K 2011PASP..123.1347K), except for the two non-KINGFISH
galaxies NGC 5194 (Ciardullo+ 2002, J/ApJ/577/31) and
NGC 2403 (Freedman+ 2001ApJ...553...47F 2001ApJ...553...47F).
Note (3): Nuclear type based on optical spectroscopy as given in Table 5 of
Moustakas+ (2010, J/ApJS/190/233) as follows:
SF = star-forming;
AGN = non-thermal emission.
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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- 14 A14 --- Name Extranuclear source identifier
16- 17 I2 h RAh Hour of right ascension (J2000)
19- 20 I2 min RAm Minute of right ascension (J2000)
22- 25 F4.1 s RAs Second of right ascension (J2000)
27 A1 --- DE- Sign of declination (J2000)
28- 29 I2 deg DEd Degree of declination (J2000)
31- 32 I2 arcmin DEm Arcminute of declination (J2000)
34- 35 I2 arcsec DEs Arcsecond of declination (J2000)
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Name Field identifier (galaxy nuclei or
extranuclear HII regions)
15 A1 --- m_Name [A-N] Source identifier (blank if
only one source in the field)
17- 18 I2 h RAh Hour of Right Ascension (J2000)
20- 21 I2 min RAm Minute of Right Ascension (J2000)
23- 27 F5.2 s RAs Second of Right Ascension (J2000)
29 A1 --- DE- Sign of the Declination (J2000)
30- 31 I2 deg DEd Degree of Declination (J2000)
33- 34 I2 arcmin DEm Arcminute of Declination (J2000)
36- 39 F4.1 arcsec DEs Arcsecond of Declination (J2000)
41 A1 --- l_S33 Limit flag on S33
43- 48 F6.2 mJy S33 [0.03/73.8] VLA 33GHz flux density
50- 53 F4.2 mJy e_S33 [0.01/2.3]? Uncertainty in S33
55 A1 --- l_fHa Limit flag on fHa
57- 62 F6.2 10-16W/m2 fHa [0.02/26]? Hα flux; 1e-13ergs/cm2/s
64- 67 F4.2 10-16W/m2 e_fHa [0.01/5.2]? Uncertainty in fHa
69- 74 F6.3 kpc rG [0.01/24] Galactocentric radius
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- Name Field identifier (galaxy nuclei or
extranuclear HII regions)
15 A1 --- m_Name [a-h] Source identifier (blank if
only one source in the field)
17- 18 I2 h RAh Hour of Right Ascension (J2000)
20- 21 I2 min RAm Minute of Right Ascension (J2000)
23- 27 F5.2 s RAs Second of Right Ascension (J2000)
29 A1 --- DE- Sign of the Declination (J2000)
30- 31 I2 deg DEd Degree of Declination (J2000)
33- 34 I2 arcmin DEm Arcminute of Declination (J2000)
36- 39 F4.1 arcsec DEs Arcsecond of Declination (J2000)
41 A1 --- l_S33 Limit flag on S33
43- 48 F6.2 mJy S33 [0.03/36.6] VLA 33GHz flux density
50- 53 F4.2 mJy e_S33 [0.01/1.1]? Uncertainty in S33
55 A1 --- l_fHa Limit flag on fHa
57- 62 F6.2 10-16W/m2 fHa [0.01/7.5]? Hα flux; 1e-13 ergs/cm2/s
64- 67 F4.2 10-16W/m2 e_fHa [0/1.5]? Uncertainty in fHa
69- 75 F7.2 mJy f24 [0.3/2161] Spitzer/MIPS 24um band flux density
77- 82 F6.2 mJy e_f24 [0.02/108.1] Uncertainty in f24
84- 89 F6.3 kpc rG [0/24] Galactocentric radius
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 19-Mar-2018