J/ApJ/761/97 Star Formation in Radio Survey (SFRS): 33GHz obs. (Murphy+, 2012)
The Star Formation in Radio Survey: GBT 33 GHz observations of nearby galaxy
nuclei and extranuclear star-forming regions.
Murphy E.J., Bremseth J., Mason B.S., Condon J.J., Schinnerer E.,
Aniano G., Armus L., Helou G., Turner J.L., Jarrett T.H.
<Astrophys. J., 761, 97 (2012)>
=2012ApJ...761...97M 2012ApJ...761...97M
ADC_Keywords: Radio continuum; Surveys; Active gal. nuclei; Galaxies, nearby;
Photometry, infrared; Photometry, ultraviolet
Keywords: cosmic rays; galaxies: nuclei; H II regions; radio continuum: general;
stars: formation
Abstract:
We present 33GHz photometry of 103 galaxy nuclei and extranuclear
star-forming complexes taken with the Green Bank Telescope (GBT) as
part of the Star Formation in Radio Survey (SFRS). Among the sources
without evidence for an active galactic nucleus, and also having lower
frequency radio data, we find a median thermal fraction at 33GHz of
~76% with a dispersion of ~24%. For all sources resolved
on scales ≲0.5kpc, the thermal fraction is even larger, being ≳90%.
This suggests that the rest-frame 33GHz emission provides a sensitive
measure of the ionizing photon rate from young star-forming regions,
thus making it a robust star formation rate (SFR) indicator. Taking
the 33 GHz SFRs as a reference, we investigate other empirical
calibrations relying on different combinations of warm 24µm dust,
total infrared (IR; 8-1000µm), Hα line, and far-UV continuum
emission. The recipes derived here generally agree with others found
in the literature, albeit with a large dispersion that most likely
stems from a combination of effects. Comparing the 33GHz to total IR
flux ratios as a function of the radio spectral index, measured
between 1.7 and 33GHz, we find that the ratio increases as the radio
spectral index flattens which does not appear to be a distance effect.
Consequently, the ratio of non-thermal to total IR emission appears
relatively constant, suggesting only moderate variations in the
cosmic-ray electron injection spectrum and ratio of synchrotron to
total cooling processes among star-forming complexes. Assuming that
this trend solely arises from an increase in the thermal fraction sets
a maximum on the scatter of the non-thermal spectral indices among the
star-forming regions of σαNT≲0.13.
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 Spitzer Infrared Nearby Galaxies Survey
(SINGS, Kennicutt et al. 2003PASP..115..928K 2003PASP..115..928K) and Key Insights on
Nearby Galaxies: a Far-Infrared Survey with Herschel (KINGFISH,
Kennicutt et al. 2011PASP..123.1347K 2011PASP..123.1347K) legacy programs. Each of these
nuclear and extranuclear star-forming complexes have ∼1'x0.5' sized
mid-IR (i.e., low resolution from 5 to 14um and high resolution from
10 to 37um) spectral mappings carried out by the Infrared Spectrograph
instrument on board Spitzer, and 47"x47" sized Herschel/PACS far-IR
spectral mappings for a combination of the principal atomic ISM
cooling lines of [OI]63um, [OIII]88um, [NII]122,205um, and [CII]158um.
Observations in the Ka band (26-40GHz) were taken using the Caltech
Continuum Backend (CCB) on the 100m Robert C. Byrd Green Bank
Telescope (GBT) over a two year period spanning 2009 March through
2011 January. The CCB simultaneously measures the entire Ka bandwidth
over four equally spaced frequency channels (i.e., 27.75, 31.25,
34.75, and 38.25GHz) and synchronously reads out and demodulates the
beam-switched signal to remove atmospheric fluctuation and/or gain
variations. The FWHM of the GBT beam across the full Ka band was
typically ∼25" among our sets of observations.
The Hα imaging used in the analysis is taken from Leroy et al.
(2012AJ....144....3L 2012AJ....144....3L). Like the archival GALEX UV data, Hα
images were corrected for foreground stars. The typical resolution of
the Hα images is ∼2".
Ancillary radio data at 1.365 and 1.697GHz for 24 of the sample
galaxies are available from the Westerbork Synthesis Radio Telescope
SINGS survey (Braun et al. 2007A&A...461..455B 2007A&A...461..455B).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 82 46 Nuclear source positions and 33GHz photometry
table2.dat 82 57 Extranuclear source positions and 33GHz photometry
table3.dat 102 46 Nuclear photometry from ancillary data
table4.dat 102 57 Extranuclear photometry from ancillary data
table6.dat 71 46 Nuclear photometry for individual Caltech Continuum
Backend (CCB) ports
table7.dat 71 57 Extranuclear photometry for individual Caltech
Continuum Backend (CCB) ports
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See also:
J/A+A/552/A19 : Radio-farIR correlation in NGC 6946 (Tabatabaei+, 2013)
J/ApJ/757/52 : UV and IR observations for SINGS galaxies. I. (Mao+, 2012)
J/ApJS/190/233 : Spectroscopy & abundances of SINGS galaxies (Moustakas+, 2010)
J/ApJ/714/1256 : Far-IR star formation rate indicators (Calzetti+, 2010)
J/ApJ/704/1433 : 31GHz survey of low-frequency radio sources (Mason+, 2009)
J/ApJ/703/1672 : Far-IR and Hα fluxes in galaxies (Kennicutt+, 2009)
J/ApJ/703/517 : The Spitzer Local Volume Legacy: IR photometry (Dale+, 2009)
J/ApJ/692/556 : Star forming galaxy templates (Rieke+, 2009)
J/ApJ/671/333 : Aperture photometry in NGC 5194 (Kennicutt+, 2007)
J/ApJ/648/987 : UV through far-IR analysis of M81 (Perez-Gonzalez+, 2006)
J/ApJS/164/38 : UV & FIR data for nearby galaxies (Iglesias-Paramo+, 2006)
J/ApJ/633/871 : Positions and photometry of HII knots in M51 (Calzetti+, 2005)
J/ApJ/577/31 : PNe in six galaxies (Ciardullo+, 2002)
J/ApJS/112/315 : Spectroscopic parameters of Seyfert nuclei (Ho+ 1997)
Byte-by-byte Description of file: table[12].dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Galaxy Galaxy name
13- 14 I2 --- Enuc [1/11]? Extranuclear ID number
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- 42 A6 --- Type Morphological type from NED (only for table 1)
44- 48 F5.2 Mpc Dist [3/30.6]? Distance (only for table 1) (1)
50- 55 A6 --- NType Nucleus type (only for table 1) (2)
57 A1 --- r_NType Reference for NType (3)
59 A1 --- l_S33 Limit flag on S33
61- 65 F5.2 mJy S33 [0.1/76.2] GBT/CCB 33GHz flux density
67- 70 F4.2 mJy e_S33 [0.02/4]? S33 uncertainty
72 A1 --- l_S33b Limit flag on S33b
74- 77 F4.2 mJy S33b [0.09/2.9]? Uncorrected 33GHz flux density (4)
79- 82 F4.2 mJy e_S33b [0.02/0.3]? S33b uncertainty
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Note (1): Redshift-independent distance taken from the list compiled by
Kennicutt et al. (2011PASP..123.1347K 2011PASP..123.1347K), except for the two
non-KINGFISH galaxies NGC 5194 (Ciardullo et al. 2002, J/ApJ/577/31)
and NGC 2403 (Freedman et al. 2001ApJ...553...47F 2001ApJ...553...47F).
Note (2): Nuclear-type-based optical spectroscopy:
SF = star forming;
AGN = non-thermal emission
Note (3): Nuclear type as given in
* Table 5 of Moustakas et al. 2010 (J/ApJS/190/233)
* Table 4 of Ho et al. 1997 (J/ApJS/112/315) if flagged "*"
Note (4): Measured 33GHz flux densities before applying a correction for
the oversubtraction of emission due to reference nods falling on
bright regions of the galaxy. Corrections were only applied to cases,
where the estimated loss is >15%.
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Byte-by-byte Description of file: table[34].dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Galaxy Galaxy name
13- 14 I2 --- Enuc [1/11]? Extranuclear ID number
16- 21 F6.1 mJy F24 [14/9562] Spitzer/MIPS 24um flux
23- 28 F6.1 mJy e_F24 [2/1695] F24 uncertainty
30- 34 F5.1 10-14W/m2 FIR [1.8/892] Total infrared (8-1000um) flux
36- 40 F5.1 10-14W/m2 e_FIR [0.3/321] FIR uncertainty
42- 46 F5.1 mJy S1.7 [0.3/505]? 1.7GHz flux density
48- 51 F4.1 mJy e_S1.7 [0/90]? S1.7 uncertainty
53- 57 F5.1 mJy S1.4 [0.9/585]? 1.4GHz flux density
59- 63 F5.1 mJy e_S1.4 [0.2/104]? S1.4 uncertainty
65- 69 F5.2 mJy FFUV [0.02/20]? GALEX far-UV (1528Å) flux
71- 74 F4.2 mJy e_FFUV [0/5]? FFUV uncertainty
76- 81 F6.2 mJy FNUV [0.1/120]? GALEX near-UV (2271Å) flux
83- 87 F5.2 mJy e_FNUV [0.03/28]? FNUV uncertainty
89- 92 F4.1 10-16W/m2 FHa [0.3/32]? Hα flux
94- 96 F3.1 10-16W/m2 e_FHa [0.1/9]? FHa uncertainty
98-102 F5.3 mag E(B-V) [0.009/0.6] Galactic extinction (5)
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Note (5): Galactic extinction taken from Schlegel et al. (1998ApJ...500..525S 1998ApJ...500..525S)
used to correct the Hα and GALEX FUV and NUV flux densities
assuming AV/E(B-V)=3.1 and the modeled extinction curves of
Weingartner & Draine (2001ApJ...548..296W 2001ApJ...548..296W) and Draine (2003ARA&A..41..241D 2003ARA&A..41..241D)
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Byte-by-byte Description of file: table[67].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Galaxy Galaxy name
13- 14 I2 --- Enuc [1/11]? Extranuclear ID number
16- 19 F4.1 mJy S22.75 [-0.6/99.8] GBT/CCB 22.75GHz flux density
21- 24 F4.2 mJy e_S22.75 [0.04/1.1] S22.75 uncertainty
26- 29 F4.1 mJy S31.25 [-4.3/85.5] GBT/CCB 31.25GHz flux density
31- 34 F4.2 mJy e_S31.25 [0.03/1] S31.25 uncertainty
36- 39 F4.1 mJy S34.75 [-3.3/73.7] GBT/CCB S34.75Ghz flux density
41- 44 F4.2 mJy e_S34.75 [0.03/0.7] S34.75 uncertainty
46- 49 F4.1 mJy S38.25 [-0.9/65.4] GBT/CCB S38.25GHz flux density
51- 54 F4.2 mJy e_S38.25 [0.04/1.4] S38.25 uncertainty
56- 60 F5.2 GHz nu0 [31/34.7] Effective frequency (νeff)
62- 63 I2 --- Nu [1/70] Number of nods used
65- 66 I2 --- Nt [2/77] Number of nods taken
68- 71 F4.1 min Ton [0.7/47] Corresponding time spent on source
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Nomenclature note:
Tables 2,5,7: extranuclear star-forming regions are
<[MBM2012] NGCNNNN Enuc. NN> in Simbad.
History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 07-Aug-2014