J/ApJS/248/25 The SFRS: 3-33GHz VLA obs. of star-forming regions (Linden+, 2020)
The Star Formation in Radio Survey: 3-33GHz imaging of nearby galaxy nuclei and
extranuclear star-forming regions.
Linden S.T., Murphy E.J., Dong D., Momjian E., Kennicutt R.C., Meier D.S.,
Schinnerer E., Turner J.L.
<Astrophys. J. Suppl. Ser., 248, 25 (2020)>
=2020ApJS..248...25L 2020ApJS..248...25L
ADC_Keywords: Active gal. nuclei; Star Forming Region; Radio sources;
Galaxies, nearby; Galaxies, IR; Photometry, H-alpha; Ultraviolet
Keywords: Star formation ; H II regions ; Radio continuum emission ; Star-
forming regions ; Radio interferometry ; Radio astronomy ; Galaxies ;
Galaxy evolution ; Spiral galaxies ; Extragalactic radio sources
Abstract:
We present 3, 15, and 33GHz imaging toward galaxy nuclei and
extranuclear star-forming regions using the Karl G. Jansky Very Large
Array as part of the Star Formation in Radio Survey (SFRS). With
3-33GHz radio spectra, we measured the spectral indices and
corresponding thermal (free-free) emission fractions for a sample of
335 discrete regions having significant detections in at least two
radio bands. After removing 14 likely background galaxies, we find
that the median thermal fraction at 33GHz is 92%±0.8% with a median
absolute deviation of 11%, when a two-component power-law model is
adopted to fit the radio spectrum. Limiting the sample to 238 sources
that are confidently identified as star-forming regions and not
affected by potential AGN contamination (i.e., having galactocentric
radii rG≥250pc) results in a median thermal fraction of 93%±0.8%
with a median absolute deviation of 10%. We further measure the
thermal fraction at 33GHz for 163 regions identified at 7" resolution
to be 94%±0.8% with a median absolute deviation of 8%. Together,
these results confirm that free-free emission dominates the radio
spectra of star-forming regions on scales up to ∼500pc in normal
star-forming galaxies. We additionally find a factor of ∼1.6 increase
in the scatter of the measured spectral index and thermal fraction
distributions as a function of decreasing galactocentric radius. This
trend is likely reflective of the continuous star formation activity
occurring in the galaxy centers, resulting in a larger contribution of
diffuse nonthermal emission relative to star-forming regions in the
disk.
Description:
The Star Formation in Radio Survey (SFRS) sample includes targeted
observations from 56 nearby galaxies (dL<30Mpc) in the Spitzer
Infrared Nearby Galaxies Survey (SINGS; Kennicutt+ 2003PASP..115..928K 2003PASP..115..928K)
and Key Insights on Nearby Galaxies: a Far-Infrared Survey (KINGFISH;
Kennicutt+ 2011PASP..123.1347K 2011PASP..123.1347K) legacy programs (Table 1).
The full sample over the entire sky consists of 118 star-forming
complexes (56 nuclei and 62 extranuclear regions), 112 of which (50
nuclei and 62 extranuclear regions; see Tables 2 and 3, respectively)
are observable with the VLA (i.e., having δ>-35°).
The observational setup and reduction procedure for the Ka-band
(29-37GHz) data (11B-032,13A-129) is described in detail in M18a
(Murphy+, 2018, J/ApJS/234/24). Observations in the S band (2-4GHz)
were taken during the 2013 VLA B-configuration cycle (13B-215) and
utilized the 8-bit sampler. Observations in the Ku band (12-18GHz)
were taken in 2014 November in the C configuration (13B-215) using the
3-bit samplers. Both sets of observations utilized the full available
bandwidth of the respective receivers.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 50 50 Galaxy properties
table2.dat 76 50 *Nuclear source positions and imaging characteristics
enuc.dat 80 62 Extranuclear source positions and imaging
characteristics (Table 3)
table4.dat 128 377 Region photometry and derived parameters
table5.dat 127 180 Region photometry and derived parameters at 7"
angular resolution
tablea1.dat 84 180 Ancillary source photometry at 7" angular resolution
tablea2.dat 61 377 Local background measurements
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Note on table2.dat: See Murphy+ (2018, J/ApJS/234/24) for the 33GHz imaging
characteristics.
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See also:
VII/155 : Third Reference Cat. of Bright Galaxies (RC3) (de Vaucouleurs+ 1991)
J/ApJ/577/31 : PNe in six galaxies (Ciardullo+, 2002)
J/ApJ/586/794 : Multiwavelength luminosities of galaxies (Bell, 2003)
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/745/95 : Herschel FIR & submm photom. of KINGFISH sample (Dale+, 2012)
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 : SEDs of radio continuum from KINGFISHER (Tabatabaei+, 2017)
J/ApJS/234/24 : VLA 33GHz obs. of star-forming regions (Murphy+, 2018)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Name Galaxy name
12- 17 A6 --- Type Morphological type from RC3 (VII/155)
19- 23 F5.2 Mpc Dist [3.05/30.6] Redshift-independent distance (1)
25- 30 A6 --- Nuc Nuclear type (2)
31 A1 --- f_Nuc [*] Flag on Nuc (3)
33- 41 A9 arcmin D25 Diameter from RC3 (VII/155)
43- 44 I2 deg inc [21/83] Inclination
46- 48 I3 deg PA [10/173] Position angle from RC3 (VII/155)
50 A1 --- f_PA [d] d: PA from Jarrett+ (2003AJ....125..525J 2003AJ....125..525J)
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Note (1): 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 (2): Nuclear type based on optical spectroscopy. Code as follows:
SF = star-forming;
AGN = nonthermal emission as given in Table 5 of Moustakas+ J/ApJS/190/233
Note (3):
* = Nuclear type based on Table 4 of
Lonsdale Persson & Helou (1987ApJ...314..513L 1987ApJ...314..513L).
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
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- 41 A9 arcsec Beam3GHz FWHM of the synthesized beam at 3GHz
43- 46 F4.1 uJy/beam Sig3GHz [12.8/45] 3GHZ point source sensitivity
σ
48- 54 F7.2 mK Tb3GHz [239/1431] 3GHz brightness temperature
sensitivity σTb
56- 64 A9 arcsec Beam15GHz FWHM of the synthesized beam at 15GHz
66- 69 F4.1 uJy/beam Sig15GHz [7.8/51] 15GHZ point source sensitivity
σ
71- 76 F6.2 mK Tb15GHz [10/133] 15GHz brightness temperature
sensitivity σTb
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Byte-by-byte Description of file: enuc.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Name Extranuclear source name
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)
37- 45 A9 arcsec Beam3GHz FWHM of the synthesized beam at 3GHz
47- 50 F4.1 uJy/beam Sig3GHz [12.8/45] 3GHZ point source sensitivity
σ
52- 58 F7.2 mK Tb3GHz [239/1431] 3GHz brightness temperature
sensitivity σTb
60- 68 A9 arcsec Beam15GHz FWHM of the synthesized beam at 15GHz
70- 73 F4.1 uJy/beam Sig15GHz [7.8/51] 15GHZ point source sensitivity
σ
75- 80 F6.2 mK Tb15GHz [9.8/133] 15GHz brightness temperature
sensitivity σTb
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Byte-by-byte Description of file: table[45].dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- OT Source type (G1)
5- 18 A14 --- Name Field identifier (galaxy nuclei or
extranuclear HII regions)
20 A1 --- m_Name Source identifier (blank if only one source
in the field)
22 A1 --- f_Name [a] Flag on Name (G2)
24- 25 I2 h RAh Hour of right ascension (J2000)
27- 28 I2 min RAm Minute of right ascension (J2000)
30- 35 F6.3 s RAs Second of right ascension (J2000)
37 A1 --- DE- Sign of declination (J2000)
38- 39 I2 deg DEd Degree of declination (J2000)
41- 42 I2 arcmin DEm Arcminute of declination (J2000)
44- 49 F6.3 arcsec DEs Arcsecond of declination (J2000)
51 A1 --- l_S3GHz Limit flag on S3GHz
53- 58 F6.2 mJy S3GHz [0.03/248.5] VLA 3GHz flux density
60- 63 F4.2 mJy e_S3GHz [0.01/1.2]? S3GHz uncertainty
65 A1 --- l_S15GHz Limit flag on S15GHz
67- 71 F5.2 mJy S15GHz [0.02/45.4] VLA 15GHz flux density
73- 76 F4.2 mJy e_S15GHz [0.01/1.4]? S15GHz uncertainty
78 A1 --- l_S33GHz Limit flag on S33GHz
80- 84 F5.2 mJy S33GHz [0.02/61.8] VLA 33GHz flux density
86- 89 F4.2 mJy e_S33GHz [0.01/1.1]? S33GHz uncertainty
91- 96 F6.1 pc Size [44/1556] Aperture size dap
98-103 F6.3 kpc rG [0/24] Deprojected galactocentric radius
105-110 F6.3 --- alpha [-1.4/0.9]? Observed slope α
from 3 to 33GHz
112-116 F5.3 --- e_alpha [0.001/0.5]? alpha uncertainty
118-122 F5.3 --- tfrac [0.05/1]? Thermal fraction at 33GHz
124-128 F5.3 --- e_tfrac [0.002/0.9]? tfrac uncertainty
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- OTa Source type, ancillary (G1)
5- 18 A14 --- Name Field identifier (galaxy nuclei or
extranuclear HII regions)
20 A1 --- m_Name Source identifier (blank if only one
source in the field)
22 A1 --- l_F1528 Limit flag on F1528
24- 30 F7.2 uJy F1528 [0.2/1733]? GALEX FUV (1528Å) flux
(fν)
32- 37 F6.2 uJy e_F1528 [0.4/260]? F1528 uncertainty
39 A1 --- l_F2271 Limit flag on F2271
41- 47 F7.2 uJy F2271 [0.4/2033]? GALEX NUV (2271Å) flux
(fν)
49- 54 F6.2 uJy e_F2271 [1/305]? F2271 uncertainty
56 A1 --- l_FHa Limit flag on FHa
58- 62 F5.3 10-16W/m2 FHa [0.01/8.2]? Hα flux
in 10-13erg/s/cm2 units (1)
64- 68 F5.3 10-16W/m2 e_FHa [0.003/1.7]? FHa uncertainty
70- 76 F7.2 mJy F24 [0.3/2076]? Spitzer/MIPS 24um flux (fν)
78- 83 F6.2 mJy e_F24 [0.02/104]? F24 uncertainty
84 A1 --- f_F24 [a] Flag on F24 (2)
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Note (1): The Hα data used in this analysis are taken from the
compilation presented in Leroy+ (2012AJ....144....3L 2012AJ....144....3L) as well as the
SINGS archive. See section 3.1.
Note (2):
a = Photometry unreliable and not reported owing to saturation by the
nucleus in the 24um image.
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Byte-by-byte Description of file: tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- OT Source type (G1)
5- 18 A14 --- Name Field identifier (galaxy nuclei or
extranuclear HII regions)
20 A1 --- m_Name Source identifier (blank if only one
source in the field)
22 A1 --- f_Name [a] Flag on Name (G2)
24- 29 F6.3 mJy bg3GHz [-0.14/16.8]? 3GHz local background value
31- 36 F6.3 mJy bg15GHz [-0.06/1.5]? 15GHz local background value
38- 43 F6.3 mJy bg33GHz [-0.2/1.4]? 33GHz local background value
45- 49 F5.3 --- f3GHzbg [0/0.37]? 3GHz fractional contribution (1)
51- 55 F5.3 --- f15GHzbg [0/0.33]? 15GHz fractional contribution (1)
57- 61 F5.3 --- f33GHzbg [0/0.26]? 33GHz fractional contribution (1)
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Note (1): The fractional contribution of the absolute value of the local
background measurement to the aperture flux density.
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Global notes:
Note (G1): Type as follows:
SFR = Star-forming regions;
bgG = likely background galaxies;
SNe = likely associated with supernovae;
AME = likely anomalous microwave emission (AME) candidates.
Note (G2): Flag as follows:
a = The aperture used for this star-forming region contained multiple
smaller individual regions.
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 20-Jul-2020