J/A+A/560/A9 AMIGA. Revision of the isolation degree (Argudo-Fernandez+, 2013)
The AMIGA sample of isolated galaxies.
XII. Revision of the isolation degree for AMIGA galaxies using the SDSS.
Argudo-Fernandez M., Verley S., Bergond G., Sulentic J., Sabater J.,
Fernandez Lorenzo M., Leon S., Espada D., Verdes-Montenegro L.,
Santander-Vela J.D., Ruiz J.E., Sanchez-Exposito S.
<Astron. Astrophys. 560, A9 (2013)>
=2013A&A...560A...9A 2013A&A...560A...9A
ADC_Keywords: Galaxies, photometry ; Spectroscopy
Keywords: galaxies: general - galaxies: fundamental parameters -
galaxies: formation - galaxies: evolution
Abstract:
To understand the evolution of galaxies, it is necessary to have a
reference sample where the effect of the environment is minimized and
quantified. In the framework of the AMIGA project (Analysis of the
interstellar Medium of Isolated GAlaxies), we present a revision of
the environment for galaxies in the Catalogue of Isolated Galaxies
(CIG, Karachentseva 1973, Cat. VII/82) using the ninth data release of
the Sloan Digital Sky Survey (SDSS-DR9).
The aims of this study are to refine the photometric-based AMIGA
sample of isolated galaxies and to provide an improvement of the
quantification of the isolation degree with respect to previous works,
using both photometry and spectroscopy.
We developed an automatic method to search for neighbours within a
projected area of 1Mpc radius centred on each primary galaxy to revise
the CIG isolation criteria introduced by Karachentseva (1973, Cat.
VII/82). The local number density at the fifth nearest neighbour and
the tidal strength affecting the CIG galaxy were estimated to quantify
the isolation degree.
Of the 636 CIG galaxies considered in the photometric study, 426
galaxies fulfil the CIG isolation criteria within 1Mpc, taking into
account projected neighbours. Of the 411 CIG galaxies considered in
the spectroscopic study, 347 galaxies fulfil the CIG isolation
criteria when a criterion about redshift difference is added. The
available redshifts allow us to reject background neighbours and thus
improve the photometric assessment. On average, galaxies in the AMIGA
sample show lower values in the local number density and the tidal
strength parameters than galaxies in denser environments such as
pairs, triplets, compact groups, and clusters.
For the first time, the environment and the isolation degree of AMIGA
galaxies are quantified using digital data. The use of the SDSS
database permits one to identify fainter and smaller-size satellites
than in previous AMIGA works. The AMIGA sample is improved by this
study, because we reduced the sample of isolated galaxies used in
previous AMIGA works by about 20%. The availability of the
spectroscopic data allows us to check the validity of the CIG
isolation criteria, which is not fully efficient. About 50% of the
neighbours considered as potential companions in the photometric study
are in fact background objects. We also find that about 92% of the
neighbour galaxies that show recession velocities similar to the
corresponding CIG galaxy are not considered by the CIG isolation
criteria as potential companions, which may have a considerable
influence on the evolution of the central CIG galaxy.
Description:
Result of the revision of the CIG isolation criteria and
quantification of the isolation degree for 636 CIG galaxies in the
photometric study, and 411 CIG galaxies in the spectroscopic study,
using data from the Ninth Data Release of the Sloan Digital Sky
Survey.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 30 636 Revision of the isolation degree using
photometric database
table4.dat 50 411 Revision of the isolation degree using
spectroscopic database
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See also:
VII/82 : Catalogue of Isolated Galaxies (Karachentseva+ 1986)
J/A+A/411/391 : AMIGA project Revised positions for CIG galaxies (Leon+ 2003)
J/A+A/436/443 : AMIGA I. Velocities of CIG galaxies (Verdes-Montenegro+ 2005)
J/A+A/449/937 : AMIGA II. Morphological refinement (Sulentic+, 2006)
J/A+A/462/507 : AMIGA III. IRAS data (Lisenfeld+, 2007)
J/A+A/470/505 : AMIGA IV. Neighbours around CIG galaxies (Verley+, 2007)
J/A+A/472/121 : AMIGA V. Isolation parameters (Verley+, 2007)
J/A+A/485/475 : AMIGA VI. Radio fluxes of the isolated galaxies (Leon+ 2008)
J/A+A/486/73 : AMIGA VII. FIR and radio study (Sabater+, 2008)
J/A+A/532/A117 : AMIGA VIII. Flux ratio asymmetry parameter (Espada+, 2011)
J/A+A/534/A102 : AMIGA IX. Molecular gas properties (Lisenfeld+, 2011)
J/A+A/540/A47 : AMIGA X. Isolated galaxy colors (Fernandez Lorenzo+, 2012)
J/A+A/545/A15 : AMIGA XI. Optical nuclear activity (Sabater+, 2012)
J/MNRAS/397/1756 : Fourier-derived parameters of CIG sample (Durbala+, 2009)
J/MNRAS/434/325 : 452 AMIGA galaxies physical param. (Fernandez Lorenzo+, 2013)
http://amiga.iaa.es : AMIGA Home Page
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- CIG CIG (VII/82) number, <K73 NNNN> in Simbad
6- 11 F6.2 arcmin r1Mpc Projected angular radius r1Mpc equal to the
adopted distance at 1 Mpc
14- 17 F4.2 --- ratio Ratio r1Mpc/r80Dp between the projected
angular radius at 1Mpc over the original field
radius used in the CIG isolation criteria
19 I1 --- isol [0/1] Result of the CIG isolation criteria:
"1" if the galaxy passes, "0" if it fails
21- 25 F5.2 --- Q [-4.2/809] Tidal strength estimate QKar,p
of similar-size neighbours
27- 30 F4.2 --- eta Local number density ηk,p of
similar-size neighbours
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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- 4 I4 --- CIG CIG (VII/82) number, <K73 NNNN> in Simbad
6 I1 --- isol [0/1] Result of the CIG isolation criteria
for neighbours within 1Mpc and
|Δv|≤500km/s (1=passes, 0=fails)
8- 9 I2 --- k500 [0/35] Number of neighbours within 1Mpc and
|Δv|≤500km/s
11- 15 F5.2 --- Q500 ?=- Tidal strength Q500 estimation using
neighbours within 1Mpc and |Δv|≤500km/s
17 I1 --- f_Q500 [0/2] Flag in Q500: 2 if k500=0, 0 if k500≥1
19- 23 F5.2 --- eta ?=- Local number density ηk,500 using
neighbours within 1Mpc and |Δv|≤500km/s
25 I1 --- f_eta [0/2] Flag in eta: 2 if k500=0, 1 if k500=1,
0 if k500≥2
27- 31 F5.2 % zcomp [0/100] Redshift completeness in the field
33- 34 I2 --- k500u [0/35] Number of neighbours within 1Mpc and
|Δv|≤500km/s using upper limits
36- 40 F5.2 --- Q500u ?=- Tidal strength Q500,ul upper limit
estimation using neighbours within 1Mpc and
|Δv|≤500km/s
42 I1 --- f_Q500u [0/2] Flag in Q500u: 2 if k500u=0, 0 if k500u≥1
44- 48 F5.2 --- eta.u ?=- Local number density ηk,500,ul upper
limit using neighbours within 1Mpc and
|Δv|≤500km/s
50 I1 --- f_eta.u [0/2] Flag in eta.u: 2 if k500u=0, 1 if k500u=1,
0 if k500u≥1
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Acknowledgements:
Maria del Carmen Argudo Fernandez, margudo(at)iaa.es
(End) Patricia Vannier [CDS] 27-Nov-2013