J/A+A/618/A172 Stellar populations of fossil galaxy groups (Corsini+, 2018)
Fossil group origins.
IX. Probing the formation of fossil galaxy groups with stellar population
gradients of their central galaxies.
Corsini E.M., Morelli L., Zarattini S., Aguerri J.A.L., Costantin L.,
D'Onghia E., Girardi M., Kundert A., Mendez-Abreu J., Thomas J.
<Astron. Astrophys. 618, A172 (2018)>
=2018A&A...618A.172C 2018A&A...618A.172C (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies ; Morphology ; Stellar distribution
Keywords: galaxies: elliptical and lenticular, cD - galaxies: formation -
galaxies: individual: NGC 6482 - galaxies: individual: NGC 7556 -
galaxies: kinematics and dynamics - galaxies: stellar content
Abstract:
Fossil groups (FGs) are galaxy aggregates with an extended and
luminous X-ray halo, which are dominated by a very massive early-type
galaxy and lack of L* objects. FGs are indeed characterized by a large
magnitude gap between their central and surrounding galaxies. This is
explained by either speculating that FGs are failed groups which
formed without bright satellite galaxies and did not suffer any major
merger, or suggesting that FGs are very old systems which had enough
time to exhaust their bright satellite galaxies through multiple major
mergers. Since major mergers leave signatures in the stellar
populations of the resulting galaxy, we study the stellar population
parameters of the brightest central galaxies (BCGs) of FGs as a
benchmark against which the formation and evolution scenarios of FGs
can be compared. We present long-slit spectroscopic observations along
the major, minor, and diagonal axis of NGC 6482 and NGC 7556, which
are the BCGs of two nearby FGs. The measurements include spatially
resolved stellar kinematics and radial profiles of line-strength
indices, which we converted into stellar population parameters using
single stellar-population models. NGC 6482 and NGC 7556 are very
massive (M*∼1*1011.5M☉) and large (D25∼50kpc) galaxies. They
host a centrally-concentrated stellar population, which is
significantly younger and more metal rich than the rest of the galaxy.
The age gradients of both galaxies are somewhat larger than those of
the other FG BCGs studied so far, whereas their metallicity gradients
are similarly negative and shallow. Moreover, they have negligible
gradients of alpha-element abundance ratio. The measured metallicity
gradients are less steep than those predicted for massive galaxies
which formed monolithically and evolved without experiencing any major
merger. We conclude that the observed FGs formed through major mergers
rather than being failed groups missing bright satellite galaxies
since the beginning.
Description:
Table A.1 (tablea1.dat) gives the r-band isophotal parameters of
NGC 7556 (mu, epsilon, PA). Table A.2 (tablea2.dat) gives the stellar
kinematic parameters (v, sigma, H3, H4) of NGC 6482 and NGC 7556 while
Table A.3 (tablea3.dat) gives their measured line-strength indices
(Hbeta, Mg2, Mgb, Fe5270, Fe5335).
Objects:
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RA (2000) DE Designation(s)
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17 51 48.83 +23 04 18.9 NGC 6482 = UGC 11009
23 15 44.47 -02 22 53.6 NGC 7556 = LEDA 70855
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 47 266 r-band isophotal parameters of NGC 7556
tablea2.dat 67 174 Kinematic parameters of NGC 6482 and NGC 7556
tablea3.dat 78 172 Line-strength indices of NGC 6482 and NGC 7556
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See also:
J/A+A/527/A143 : RX J105453.3+552102 cluster SDSS photometry (Aguerri+, 2011)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 6 F6.2 arcsec a Semimajor axis
8- 13 F6.3 mag/arcsec2 mu r-band surface brightness
15- 19 F5.3 mag/arcsec2 e_mu Error on mu (-1σ)
21- 25 F5.3 mag/arcsec2 E_mu Error on mu (+1σ)
27- 31 F5.3 --- ell Ellipticity
33- 37 F5.3 --- e_ell Error of ell
39- 43 F5.1 deg PA Major-axis position angle measured from
north to east
45- 47 F3.1 deg e_PA Error of PA
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- --- [NGC]
5- 8 I4 --- NGC NGC number
10- 14 F5.1 arcsec r Distance from galaxy center
16- 21 F6.1 km/s v Line of sight mean velocity
23- 26 F4.1 km/s e_v Error of v
28- 32 F5.1 km/s sigma Line of sight velocity dispersion
34- 37 F4.1 km/s e_sigma Error of sigma
39- 44 F6.3 --- H3 3rd order coeff. of Gaussian Hermite
decomposition of the line of sight velocity
distribution (LOSVD)
46- 50 F5.3 --- e_H3 Error of H3
52- 57 F6.3 --- H4 4th order coeff. of Gaussian Hermite
decomposition of the LOSVD
59- 63 F5.3 --- e_H4 Error of H4
65- 67 I3 deg PA Slit position angle measured from north to
east
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Byte-by-byte Description of file: tablea3.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- --- [NGC]
5- 8 I4 --- NGC NGC number
10- 14 F5.1 arcsec r Distance from galaxy center
16- 20 F5.3 0.1nm Hbeta Line-strength index Hbeta
22- 26 F5.3 0.1nm e_Hbeta Error of Hbeta
28- 32 F5.3 mag Mg2 Line-strength index Mg2
34- 38 F5.3 mag e_Mg2 Error of Mg2
40- 44 F5.3 0.1nm Mgb Line-strength index Mgb
46- 50 F5.3 0.1nm e_Mgb Error of Mgb
52- 56 F5.3 0.1nm Fe5270 Line-strength index Fe5270
58- 62 F5.3 0.1nm e_Fe5270 Error of Fe5270
64- 68 F5.3 0.1nm Fe5335 Line-strength index Fe5335
70- 74 F5.3 0.1nm e_Fe5335 Error of Fe5335
76- 78 I3 deg PA Slit position angle measured from north to
east
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Acknowledgements:
Enrico Maria Corsini, enricomaria.corsini(at)unipd.it
References:
Aguerri et al., Paper I 2011A&A...527A.143A 2011A&A...527A.143A, Cat. J/A+A/527/A143
Mendez-Abreu et al., Paper II 2012A&A...537A..25M 2012A&A...537A..25M
Girardi et al., Paper III 2014A&A...565A.115G 2014A&A...565A.115G
Zarattini et al., Paper IV 2014A&A...565A.116Z 2014A&A...565A.116Z
Zarattini et al., Paper V 2015A&A...581A..16Z 2015A&A...581A..16Z
Kundert et al., Paper VI 2015MNRAS.454..161K 2015MNRAS.454..161K
Zarattini et al., Paper VII 2016A&A...586A..63Z 2016A&A...586A..63Z
Aguerri et al., Paper VIII 2018A&A...609A..48A 2018A&A...609A..48A
(End) Patricia Vannier [CDS] 21-Sep-2018