J/A+A/646/A146 VVV galaxies behind Galactic bulge overdensity (Galdeano+, 2021)
Overdensity of VVV galaxies behind the Galactic bulge.
Galdeano D., Pereyra L., Duplancic F., Coldwell G., Alonso S., Ruiz A.N.,
Cora S., Perez N., Vega-Martinez C., Minniti D.
<Astron. Astrophys. 646, A146 (2021)>
=2021A&A...646A.146G 2021A&A...646A.146G (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, photometry ; Photometry, infrared
Keywords: catalogs - Galaxy: bulge - surveys - galaxies: photometry -
galaxies: statistics - methods: numerical
Abstract:
The extragalactic vision we have through the Milky Way is very
unclear. There is significant extinction of the optical emission from
objects located in the region called the Zone of Avoidance (ZOA). NIR
wavelengths are less affected by extinction, and therefore the
infrared surveys in this zone are a potential source of astronomical
discoveries. Nevertheless, these observations need to be compared with
cosmological simulations in order to carry out high-accuracy studies.
Our aim is to identify extragalactic sources in the ZOA, using
infrared images of the VVV survey. We consider mock galaxy catalogues
in order to interpret observational results.
We studied a region of 1.636 square degrees corresponding to the VVV
tile b204. Using SExtractor, we analysed photometric data generating a
catalogue of extended sources in this area. In order to confirm these
sources as galaxy candidates we visually inspected RGB images looking
for typical galaxy features. Using 2MASX and GCMW catalogued sources
we tested completeness and contamination of our catalogue and define
suitable colour cuts to select galaxies. We also compared the
observational results with those obtained from two semi-analytical
models on Dark Matter simulations. One galaxy catalogue was
constructed with the SAG semi-analytic model of galaxy formation, and
the other one was constructed with the L-Galaxies semi-analytic model.
By adopting CLASS_STAR<0.5, r1/2>0.7 arcsec and specific colour cuts
(J-Ks>0.97, J-H>0 and H-Ks>0) we generated an automatic catalogue of
extended sources. After visual inspection we identified 624 sources
with 10<Ks<17 as galaxy candidates.The contamination of the automatic
catalogue is 28% when considering visually confirmed galaxies as
reliable objects. The estimated completeness is 87% up to magnitude
Ks=13.5. We analysed the spatial distribution of galaxy candidates,
finding a high concentration of galaxies in a small region of 15
arcmin radius. This region has three times higher density than similar
areas in the tile. We compared the number of galaxies in this small
area with the mean density values obtained from a suitable sample of
galaxies from semi-analytic models finding that our results are
consistent with an overdensity region.
Using VVV near-infrared data and mock catalogues we detect new
extragalactic sources that have not been identified by other
catalogues. We demonstrate the potentiality of the VVV survey in
finding and studying a large number of galaxy candidates and
extragalactic structures obscured by the Milky Way.
Description:
In the present work, we use data from the tile b204 located in the
Galactic bulge at l=355.182° and b=-9.68974°
(α=273.72° and β=-37.87°). This tile was selected
because of its position at the edge of the bulge, which implies a low
stellar density and also low extinction, relative to the tiles in the
center of the bulge and disc, within the VVV survey area. Searching
for extragalactic sources in the tile b204 allows us to test a
reliable method for galaxy identification in the bulge area of the VVV
survey.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
catalog.dat 145 624 Catalogue of VVV galaxies behind the Milky Way
(corrected version, 05-Jul-2022)
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See also:
J/AJ/144/127 : 204 galaxy cand. from VVV infrared photometry (Amores+, 2012)
J/AJ/155/46 : Extragalactic candidates in the VVV survey (Baravalle+, 2018)
Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
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1- 22 A22 --- VVV Unique identifier in IAU naming convention
VVVJHHMMSS.ss+DDMMSS.s
24- 25 I2 h RAh Right Ascension (J2000)
27- 28 I2 min RAm Right Ascension (J2000)
30- 34 F5.2 s RAs Right Ascension (J2000)
36 A1 --- DE- Declination sign (J2000)
37- 38 I2 deg DEd Declination (J2000)
40- 41 I2 arcmin DEm Declination (J2000)
43- 46 F4.1 arcsec DEs Declination (J2000)
48- 52 F5.2 mag Ksmagap3 [11.97/17.38] Aperture magnitude
within 3 pixels in Ks
54- 57 F4.2 mag e_Ksmagap3 Error on Aperture magnitude
within 3 pixels in Ks
59- 63 F5.2 mag Hmagap3 [12.31/18.38] Aperture magnitude
within 3 pixels in H
65- 68 F4.2 mag e_Hmagap3 Eror on Aperture magnitude
within 3 pixels in H
70- 74 F5.2 mag Jmagap3 [13.02/19.35] Aperture magnitude
within 3 pixels in J
76- 79 F4.2 mag e_Jmagap3 Error on Aperture magnitude
within 3 pixels in J
81- 85 F5.2 mag Ksmag [9.99/17.02] Total magnitude Ks
87- 90 F4.2 mag e_Ksmag Error on Total magnitude Ks
92- 96 F5.2 mag Hmag [10.29/17.93] Total magnitude H
98-101 F4.2 mag e_Hmag Error on Total magnitude H
103-107 F5.2 mag Jmag [10.49/18.95] Total magnitude J
109-112 F4.2 mag e_Jmag Error on Total magnitude J
114-117 F4.2 --- S/G [0/0.5] Stellarity parameter (0 for galaxy)
119-122 F4.2 arcsec R1/2 Half light radius
124-145 A22 --- OName Source name in other surveys
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Acknowledgements:
Daniela Galdeano, dgaldeano(at)unsj-cuim.edu.ar
History:
19-Feb-2021: on-line version
05-Jul-2022: corrected version (from author)
(End) Daniela Galdeano [UNSJ], Patricia Vannier [CDS] 26-Dec-2020