J/AJ/150/81 CHANG-ES. IV. VLA D-configuration observations (Wiegert+, 2015)
CHANG-ES. IV. Radio continuum emission of 35 edge-on galaxies observed with the
Karl G. Jansky Very Large Array in D Configuration--Data Release 1.
Wiegert T., Irwin J., Miskolczi A., Schmidt P., Mora S.C.,
Damas-Segovia A., Stein Y., English J., Rand R.J., Santistevan I.,
Walterbos R., Krause M., Beck R., Dettmar R.-J., Kepley A., Wezgowiec M.,
Wang Q.D., Heald G., Li J., MacGregor S., Johnson M., Strong A.W.,
DeSouza A., Porter T.A.
<Astron. J., 150, 81 (2015)>
=2015AJ....150...81W 2015AJ....150...81W (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, radio ; Radio continuum
Keywords: galaxies: magnetic fields - galaxies: star formation -
ISM: magnetic fields - radio continuum: galaxies
Abstract:
We present the first part of the observations made for the Continuum
Halos in Nearby Galaxies, an EVLA Survey (CHANG-ES) project. The aim
of the CHANG-ES project is to study and characterize the nature of
radio halos, their prevalence as well as their magnetic fields, and
the cosmic rays illuminating these fields. This paper reports
observations with the compact D configuration of the Karl G. Jansky
Very Large Array (VLA) for the sample of 35 nearby edge-on galaxies of
CHANG-ES. With the new wide bandwidth capabilities of the VLA, an
unprecedented sensitivity was achieved for all polarization products.
The beam resolution is an average of 9.6" and 36" with noise levels
reaching approximately 6 and 30µJy/beam for C- and L-bands,
respectively (robust weighting). We present intensity maps in these
two frequency bands (C and L), with different weightings, as well as
spectral index maps, polarization maps, and new measurements of star
formation rates (SFRs). The data products described herein are
available to the public in the CHANG-ES data release available at
http://www.queensu.ca/changes. We also present evidence of a trend
among galaxies with larger halos having higher SFR surface density,
and we show, for the first time, a radio continuum image of the median
galaxy, taking advantage of the collective signal-to-noise ratio of 30
of our galaxies. This image shows clearly that a "typical" spiral
galaxy is surrounded by a halo of magnetic fields and cosmic rays.
Description:
This is the fourth paper in the series "Continuum Halos in Nearby
Galaxies, an EVLA Survey" (CHANG-ES).
With CHANG-ES, we have observed 35 nearby edge-on galaxies in the
radio continuum in L- and C-bands (centered at approximately 1.5 and
6GHz, respectively), in three array configurations (B, C, D; in the B
configuration only L-band was observed) of the Karl G. Jansky Very
Large Array (hereafter VLA). We refer to Table1 of Irwin et al.
(2012AJ....144...43I 2012AJ....144...43I; Paper I) for details of the galaxy sample.
Two other papers, Irwin et al. (2012AJ....144...44I 2012AJ....144...44I; Paper II) and
Irwin et al. (2013AJ....146..164I 2013AJ....146..164I; Paper III), present the detailed
results of CHANG-ES observations of NGC 4631 and UGC 10288,
respectively.
In this, the fourth CHANG-ES paper, we present all observations that
were carried out in the shortest baseline array configuration, D. The
data products (including intensity maps, spectral index maps, and
polarization maps) are part of our Data Release 1, located at
http://www.queensu.ca/changes.
Of the 405hr that were awarded for the entire CHANG-ES project, 65hr
were set apart for the D-configuration observations in two frequency
bands, L and C. The observations were divided up into 13 scheduling
blocks. The bulk of the data were observed during 2011 December. Two
scheduling blocks were reobserved in 2013 March. The details of the
observations are presented in Table1.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 81 81 Observations
table4.dat 90 70 Imaging results for the C band
table5.dat 90 70 Imaging results for the L band
table6.dat 51 35 Star formation rates
table7.dat 37 35 Flux densities
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See also:
http://www.queensu.ca/changes : CHANG-ES
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Galaxy name
10 A1 --- f_Name [*] Flag "*" indicates large galaxies observed
in two pointings in C-band (1)
12- 13 I2 h RAh Hour of Right Ascension (J2000)
15- 16 I2 min RAm Minute of Right Ascension (J2000)
18- 22 F5.2 s RAs Second of Right Ascension (J2000)
24 A1 --- DE- Sign of the Declination (J2000)
25- 26 I2 deg DEd Degree of Declination (J2000)
28- 29 I2 arcmin DEm Arcminute of Declination (J2000)
31- 34 F4.1 arcsec DEs Arcsecond of Declination (J2000)
36- 40 F5.2 Mpc Dist [4.4/42] Distance
41 A1 --- f_Dist [V*] Flag on Dist: *=updated distance (see
Section 2.1.2) derived with TGRB;
V=Virgo cluster galaxy)
43 A1 --- Band [CL] Band (C or L) (G1)
45- 50 I6 "YYMMDD" Date Date of observation (yymmdd)
52- 58 I7 --- SB [4806011/6621021] Scheduling Block
identification number (3)
60- 64 A5 --- Cal1 Primary leakage calibrator (4)
66- 70 A5 --- Cal0 Zero polarization leakage calibrator (4)
72- 81 A10 --- Cal2 Secondary leakage calibrator
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Note (1): Eight galaxies in the sample are too large to fit inside the primary
beam of 7.5' FWHM at C-band (see Section 2.2.1 for more details).
Note (3): The observations were divided up into 13 scheduling blocks, each of
which contained scans of one primary gain and phase calibrator (hereafter
referred to as the primary calibrator) and one zero polarization calibrator
to calibrate polarization leakage from the instrumentation. Additionally,
complex gain calibrations were performed using a source (hereafter the
secondary calibrator) less than 10° from the target galaxy (see
Section 2.2 for additional details).
Note (4): Alternate name for primary and leakage calibrators:
3C84 = J0319+4130;
3C286 = J1331+305;
3C48 = OQ208 = QSO B1404+2841 or J1407+2827.
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Byte-by-byte Description of file: table[45].dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Galaxy name
11 A1 --- f_Name [a] Flag "a" on Name indicates that map peak
and polarization peak values given for
UGC10288 are of the background source
13- 17 A5 --- Weight Weighting (rob 0 or uvtap) (1)
19- 21 A3 --- f_Weight Flag on Weight (n/a)
23- 27 F5.2 arcsec Bmaj [8.8/76.6]? Synthesized beam major axis
29- 33 F5.2 arcsec Bmin [8/51.2]? Synthesized beam minor axis
35- 42 F8.3 deg BPA [-180/88.1]? Synthesized beam position angle
44- 50 F7.5 GHz v0 ? Band central frequency
(varying due to differences in flagging)
52- 56 F5.1 uJy/beam rmsI [5/150]? Stokes I rms noise (2)
58- 64 F7.3 mJy/beam IPk1 [0.2/614]? Map peak intensity of the
galaxy (3)
66- 71 F6.2 mJy/beam IPk2 [1.3/296.2]? Second value of galaxy peak
intensity (3)
73- 77 I5 --- DR [42/70116]? Dynamic range in image (map peak
intensity over noise)
79- 82 F4.1 uJy/beam rmsQU [5/65]? Stokes Q and U average rms noise (4)
83 A1 --- f_rmsQU [b] Flag "b" on rmsQU indicates a previous
observation (5)
85- 90 F6.1 uJy/beam IPk3 [14.3/3027]? Peak intensity of the
polarization map (measured from non primary
beam corrected maps)
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Note (1): Weighting defined as below:
rob 0 = Briggs (1995 PhD thesis New Mexico Institute of Mining and
Technology) weighting with robust value set to 0. See Section 3.3.1
for additional details;
uvtap = An uv-tapered version of the former (see details in Section 3.3.1).
Note (2): Each imaging run was cleaned down to a flux density level of
2.5-3σ. With few exceptions, we imaged the entire field
(i.e., without specifying regions) because a lower rms could be obtained
with this strategy. See Section 3.3.2 for details about the Stokes I
imaging.
Note (3): When two values are given, the first value is the peak intensity of
the galaxy, and the second higher value is the peak of the map when this
occurs outside of the galaxy.
Note (4): Stokes Q and U images were produced similarly to I. These maps were
used to create polarization intensity and polarization angle maps.
See further details in Section 3.3.3.
Note (5): A previous observation (an extra 10 minutes on source) was included
in the L-band Stokes Q and U imaging to increase sensitivity. It was,
however, excluded from Stokes I imaging due to artifact contamination.
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Galaxy name
11- 14 F4.2 Jy S22 [0.06/7.7] Flux density at 22µm
16- 19 F4.2 10-13W/m2 F22 [1/10] Flux at 22µm (1)
21- 25 F5.2 arcmin Diam1 [0.7/11.6] Angular diameter
27- 31 F5.2 kpc Diam2 [3.9/36.1] Diameter
33- 36 F4.2 Msun/yr SFR [0.02/7.3] Star Formation Rate (2)
38 A1 --- f_SFR [ab] Flag on SFR (3)
40- 44 F5.2 mMsun/yr/kpc2 SigSFR [0.1/30] Star Formation Rate surface
density (2)
46 A1 --- f_SigSFR [ab] Flag on SigSFR (a or b) (3)
48- 51 F4.2 mMsun/yr/kpc2 e_SigSFR [0.02/0.05] Fractional error on surface
density
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Note (1): These values were used for Figure3 in the paper.
Note (2): SFRs and "surface densities" are based largely on Wide-field Infrared
Survey Explorer (WISE; see cat. II/328) 22µm images. See Section 5.2 for
additional details.
Note (3): Flag defined as follows:
a = The SFR and SFR surface density values of NGC 3735 were adjusted from 4.71
and 0.005, respectively, to the values given here (lower limits), in order
to account for the central AGN (see Section 5.2.1);
b = The SFR and SFR surface density values of NGC 4388 were adjusted from 1.91
and 0.020, respectively, to the values given here (lower limits), in order
to account for the central AGN (see Section 5.2.1).
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Galaxy name
11- 16 F6.2 mJy SC Flux density C-band (central frequency 6GHz) (4)
18- 21 F4.1 mJy e_SC Uncertainty of flux density C-band (5)
23 A1 --- f_SC Flag "a" indicates that the error between
the two weightings is larger than the 2%
calibration error (6)
25- 30 F6.1 mJy SL Flux density L-band
(central frequency 1.575GHz) (4)
32- 35 F4.1 mJy e_SL Uncertainty of flux density L-band (5)
37 A1 --- f_SL Flag "a" indicates that the error between
the two weightings is larger than the 2%
calibration error (6)
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Note (4): The flux densities are the average of measurements taken at the two
weightings (robust 0 and the robust 0 with a uv tapering applied).
See Section 5.1 for more details.
Note (5): In most cases 2% calibration error.
Note (6): And in this case, we use the former.
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Global Notes:
Note (G1): The two bands are defined as below:
C = The C-band (central frequency 6.000GHz) cover a bandwidth of 2GHz
(4.979-7.021GHz) in 16 spectral windows and 1024 spectral channels
(64 in each spectral window);
L = The L-band (central frequency 1.575GHz) observations cover a bandwidth
of 512MHz (1.247-1.503GHz, 1.647-1.903GHz) in 32 spectral windows and
2048 spectral channels. In L-band, we placed the two base bands, of 16
spectral windows each, 144MHz apart in order to avoid a region of
particularly strong and contaminating Radio Frequency Interference (RFI).
History:
From electronic version of the journal
References:
Irwin et al. Paper I 2012AJ....144...43I 2012AJ....144...43I
Irwin et al. Paper II 2012AJ....144...44I 2012AJ....144...44I
Irwin et al. Paper III 2013AJ....146..164I 2013AJ....146..164I
(End) Sylvain Guehenneux [CDS] 11-Apr-2016