J/MNRAS/448/3731 Local Group dSph radio survey with ATCA (Regis+, 2015)
Local Group dSph radio survey with ATCA -
I: observations and background sources.
Regis M., Richter L., Colafrancesco S., Massardi M., De Blok W.J.G.,
Profumo S., Orford N.
<Mon. Not. R. Astron. Soc., 448, 3731-3746 (2015)>
=2015MNRAS.448.3731R 2015MNRAS.448.3731R (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Radio sources
Keywords: catalogues - galaxies: dwarf - radio continuum: galaxies
Abstract:
Dwarf spheroidal (dSph) galaxies are key objects in near-field
cosmology, especially in connection to the study of galaxy formation
and evolution at small scales. In addition, dSphs are optimal targets
to investigate the nature of dark matter. However, while we begin to
have deep optical photometric observations of the stellar population
in these objects, little is known so far about their diffuse emission
at any observing frequency, and hence on thermal and non-thermal
plasma possibly residing within dSphs. In this paper, we present deep
radio observations of six local dSphs performed with the Australia
Telescope Compact Array (ATCA) at 16cm wavelength. We mosaicked a
region of radius of about 1° around three 'classical' dSphs,
Carina, Fornax, and Sculptor, and of about half of degree around three
'ultrafaint' dSphs, BootesII, Segue2, and Hercules. The rms noise
level is below 0.05 mJy for all the maps. The restoring beams full
width at half-maximum ranged from 4.2"x2.5" to 30.0"x2.1" in the most
elongated case. A catalogue including the 1392 sources detected in the
six dSph fields is reported. The main properties of the background
sources are discussed, with positions and fluxes of brightest objects
compared with the FIRST, NVSS, and SUMSS observations of the same
fields. The observed population of radio emitters in these fields is
dominated by synchrotron sources. We compute the associated source
number counts at 2GHz down to fluxes of 0.25mJy, which prove to be
in agreement with AGN count models.
Description:
We present a catalogue of radio sources detected in the fields of six
dwarf spheroidal galaxies of the Local Group, which are Carina,
Fornax, Sculptor, BootesII, Segue2, and Hercules.
Observations were performed during July/August 2011 with the six 22-m
diameter Australia Telescope Compact Array antennae operating at 16cm
wavelength.
We mosaicked a region of radius of about one degree around the first
three dwarfs, and of about half of degree around the last three
dwarfs.
The rms noise level is below 0.05mJy. The restoring beams FWHM ranged
from 4.2x2.5-arcseconds to 30.0x2.1-arcseconds in the most
elongated case.
The catalogue includes different parameters describing 1835 entries
which, in our classification, correspond to 1392 sources.
See the publication for more details.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 72 1834 Catalogue of radio sources in the fields of the
dwarf spheroidal galaxies Carina, Fornax,
Sculptor, Bootes II, Segue 2, and Hercules
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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- 2 I2 h RAh Right ascension (J2000)
4- 5 I2 min RAm Right ascension (J2000)
7- 10 F4.1 s RAs Right ascension (J2000) (1)
12 A1 --- DE- Declination sign (J2000)
13- 14 I2 deg DEd Declination (J2000)
16- 17 I2 arcmin DEm Declination (J2000)
19- 22 F4.1 arcsec DEs Declination (J2000) (1)
24- 29 F6.2 mJy Fp Peak flux density at 2GHz (un-tapered map) (2)
31- 36 F6.2 mJy Fint Integrated flux density at 2GHz (un-tapered map)
38- 42 F5.2 mJy e_Fint Error on integrated flux density (3)
44- 47 F4.2 arcmin bmaj FWHM major axis of the source (4)
49- 52 F4.2 arcmin bmin FWHM minor axis of the source (4)
54- 59 F6.2 deg PA [] Source position angle (north to east) (4)
61- 66 F6.2 deg Fgt Integrated flux density at 2GHz in the
tapered map
68- 72 A5 --- MFlag Flag for multiple component sources (5)
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Note (1): The positional uncertainty amounts to about 1 arcsec.
Note (2): Peak flux densities are not corrected for possible systematic effects,
which are estimated to be negligible (see discussion in the publication).
Note (3): Errors on integrated flux density are obtained summing in quadrature
the local rms, the fit error, and a 5% of the flux density (to account for
possible inaccuracy in the calibration model and process, especially due to
RFI).
Note (4): When F/Fp<1.3, the source is not successfully deconvolved and these
values should not be considered.
Note (5): Flag for multiple component sources as follows:
S = single component source
M = multiple component source, followed by a number, identifying the
multiple source to which the component belongs, and a letter identifying
the field
(a=Carina, b=Fornax, c=Sculptor, d=BootesII, e=Hercules, f=Segue2)
* = Source present in the tapered map, but not in the un-tapered map.
In this case, all the properties in the other columns are derived from
the tapered map.
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History:
From electronic version of the journal
Acknowledgements:
Marco Regis, University of Turin and INFN, Italy
References:
Regis et al., Paper II 2015MNRAS.448.3747R 2015MNRAS.448.3747R
(End) Marco Regis [Turin Univ & INFN, Italy], Patricia Vannier [CDS] 17-Sep-2015