J/AJ/144/78 Spectroscopy of early-type galaxies in A262 (Wegner+, 2012)
Further evidence for large central mass-to-light ratios in early-type galaxies:
the case of ellipticals and lenticulars in the A262 cluster.
Wegner G.A., Corsini E.M., Thomas J., Saglia R.P., Bender R., Pu S.B.
<Astron. J., 144, 78 (2012)>
=2012AJ....144...78W 2012AJ....144...78W
ADC_Keywords: Abundances ; Spectroscopy ; Galaxies, spectra ; Morphology ;
Rotational velocities ; Velocity dispersion
Keywords: galaxies: abundances - galaxies: elliptical and lenticular, cD -
galaxies: formation - galaxies: kinematics and dynamics -
galaxies: stellar content
Abstract:
We present new radially resolved spectroscopy of eight early-type
galaxies in the A262 cluster. The measurements include stellar
rotation, velocity dispersion, H3 and H4coefficients of the
line-of-sight velocity distribution along the major and minor axes and
an intermediate axis as well as line-strength index profiles of Mg,
Fe, and Hβ. The ionized-gas velocity and velocity dispersion is
measured for six sample galaxies along different axes. We derive
dynamical mass-to-light ratios and dark matter densities from
orbit-based dynamical models, complemented by the galaxies' ages,
metallicities, and α-element abundances from single
stellar-population models. The ionized-gas kinematics give a valuable
consistency check for the model assumptions about orientation and
intrinsic shape of the galaxies. Four galaxies have a significant
detection of dark matter and their halos are about 10 times denser
than in spirals of the same stellar mass. By calibrating dark matter
densities to cosmological simulations we find assembly redshifts of
zDM~1-3, as previously reported for the Coma Cluster. The
dynamical mass that follows the light is larger than expected for a
Kroupa stellar initial mass function (IMF), especially in galaxies
with high velocity dispersion σeff inside the effective radius
reff. This could indicate a "massive" IMF in massive galaxies.
Alternatively, some of the dark matter in massive galaxies could
follow the light very closely. In combination with our comparison
sample of Coma early-type galaxies, we now have 5 of 24 galaxies where
(1) mass follows light to 1-3reff, (2) the dynamical mass-to-light
ratio of all the mass that follows the light is large (~8-10 in
the Kron-Cousins R band), and (3) the dark matter fraction is
negligible to 1-3reff. Unless the IMF in these galaxies is
particularly "massive" and somehow coupled to the dark matter content,
there seems to be a significant degeneracy between luminous and dark
matter in at least some early-type galaxies. The role of violent
relaxation is briefly discussed.
Description:
All the sample galaxies in A262 were studied within the EFAR
(Ellipticals FAR away) project. The EFAR project was aimed at
constructing an accurate and homogeneous photometric and spectroscopic
database for a large sample of early-type galaxies at redshifts
between 6000 and 15000km/s and distributed in 85 clusters in the
Hercules-Corona Borealis and Perseus-Pisces-Cetus regions. Details
about the selection of the EFAR galaxy and cluster sample are given by
Wegner et al. (1996, Cat. J/ApJS/106/1). Saglia et al. (1997, Cat.
J/MNRAS/292/499) and Wegner et al. (1999, Cat. J/MNRAS/305/259)
presented the photometric and spectroscopic databases, respectively.
The galaxies studied here were selected to be round and were
classified as early-type (cD, E, and E/S0) in Wegner et al. (1996,
Cat. J/ApJS/106/1).
As part of the HST Snapshot Proposal 10884 (P.I.: G. A. Wegner), the
galaxies NGC 679, NGC 687, NGC 708, NGC 759, and UGC 1308, were
observed with the Wide Field Planetary Camera 2 (WFPC2) on board the
Hubble Space Telescope (HST) between 2007 July 14 and 2008 September
27. For each galaxy, two 300s exposures were taken with the filter
F622W.
Long-slit spectroscopic data of the sample galaxies were obtained with
the 2.4m Hiltner telescope of the MDM Observatory at Kitt Peak, AZ on
2003 November 14-23 (run 1), 2005 October 25-31 (run 2), and 2006
November 10-16 (run 3). In runs 1 and 2 the telescope was mounted on
the Moderate Resolution Spectrograph. The "Echelle" CCD was adopted as
detector. In run 3 the Boller & Chivens CCD Spectrograph was mounted.
The "Ohio State University Loral C" CCD was the detector. The
wavelength range was from 4670 to 6541Å in run 1, from 4675 to
6530Å in run 2, and from 6270 to 7175Å in run 3.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 58 8 Properties of the sample galaxies
table2.dat 30 38 Log of the spectroscopic observations
table5.dat 120 463 Photometric parameters of the sample galaxies
table6.dat 70 293 Stellar kinematics of the sample galaxies
table7.dat 45 106 Ionized-gas kinematics of the sample galaxies
table8.dat 81 293 Line-strength indices of the sample galaxies
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
VII/237 : HYPERLEDA. I. Catalog of galaxies (Paturel+, 2003)
VII/110 : Rich Clusters of Galaxies (Abell+ 1989)
J/A+A/509/A61 : Long slit spectroscopy in M31 (Saglia+, 2010)
J/A+A/516/A4 : NGC1600, NGC4125, NGC7619 extended spectroscopy (Pu+, 2010)
J/ApJ/705/1099 : The Sloan Lens ACS (SLACS) Survey. IX. (Auger+, 2009)
J/ApJS/175/462 : Spectroscopy of Coma early-type galaxies (Corsini+, 2008)
J/ApJ/621/673 : Line indices for 124 early-type galaxies (Thomas+, 2005)
J/A+A/407/423 : Coma cluster early-type galaxies. III. (Mehlert+, 2003)
J/AJ/126/2268 : Velocity dispersions & Mg2 index of galaxies (Wegner+, 2003)
J/A+A/395/753 : Spectroscopy of Coma early-type galaxies. II. (Wegner+, 2002)
J/MNRAS/321/277 : EFAR Catalog. VII. (Colless+, 2001)
J/A+AS/141/449 : Coma cluster early-type galaxies (Mehlert+, 2000)
J/MNRAS/305/259 : EFAR redshifts & velocity dispersions (Wegner+, 1999)
J/AJ/116/2738 : Spectroscopy of early-type galaxies (Scodeggio+ 1998)
J/MNRAS/292/499 : EFAR photometric data (Saglia+, 1997)
J/ApJS/106/1 : EFAR cluster and galaxy selection (Wegner+, 1996)
J/A+AS/120/489 : Galaxies morphology and IR photometry I. (Gavazzi+ 1996)
J/A+AS/74/315 : 327 MHz Survey of the A262 cluster region (Righetti+, 1988)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Name Galaxy name
10- 15 A6 --- OName Other name (from Wegner et al., 1996,
Cat. J/ApJS/106/1)
17- 20 A4 --- MType Morphological type (from Wegner et al.,
1996, Cat. J/ApJS/106/1)
22 A1 --- n_MType a = In spite of the cD classification, the
properties of NGC 708 are not particularly
extreme with respect to the other A262
galaxies listed here)
24- 28 F5.2 arcsec Rad Effective radius obtained by Saglia et
al. (1997, cat. J/MNRAS/292/499) in the
Kron-Cousins R band
30- 34 F5.2 mag/arcsec2 Average surface brightness within the
effective radius obtained by Saglia et al.
(1997, cat. J/MNRAS/292/499) in the
Kron-Cousins R band (1)
36- 40 F5.2 mag Rmag Total magnitude measured by Saglia et al.
(1997, cat. J/MNRAS/292/499) in the
Kron-Cousins R band (2)
42- 44 I3 deg PA ? Major-axis position angle measured north
through east from the HyperLeda catalog of
galaxies (Paturel et al., 2003, VII/237)
46- 49 I4 km/s Vsys Heliocentric systemic velocity from
Wegner et al. (1999, Cat. J/MNRAS/305/259)
51- 53 I3 km/s sigma Velocity dispersion σ measured by
Wegner et al. (1999, J/MNRAS/305/259) (3)
55- 58 F4.2 Mpc dist Projected distance from NGC 708
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Note (1): After applying the Galactic absorption, KR and cosmological
dimming corrections.
Note (2): After applying the Galactic absorption and KR corrections.
Note (3): After applying the correction to the standard metric aperture of
0.54h-1kpc in radius.
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Name Galaxy name
10 I1 --- R Observing run (G1)
12- 14 I3 deg PA Slit position angle measured north through east
16- 17 A2 --- S Slit position (MJ = major axis, or close to the
major axis; MN = minor axis, or close to the
minor axis; DG = diagonal axis)
19 I1 --- N Number of exposures
21- 24 I4 s Exp1 Exposure time (of the single exposures)
26- 28 F3.1 h Exp2 Total exposure time
30 I1 --- Q Estimated quality of the resulting spectrum
(1=excellent; 2=very good; 3=good; 4=fair).
See Figure 3 in this paper.
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Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Name Galaxy name
10- 15 F6.3 arcsec a Semi-major axis
17- 21 F5.3 arcsec e_a Uncertainty in a
23- 28 F6.3 mag/arcsec2 muR Azimuthally-averaged R band surface
brightness
30- 34 F5.3 mag/arcsec2 e_muR Uncertainty in muR
36- 40 F5.3 --- e Ellipticity
42- 46 F5.3 --- e_e Uncertainty in e
48- 52 F5.1 deg PA Position angle
54- 58 F5.1 deg e_PA Uncertainty in PA
60- 65 F6.3 arcsec Xpos X position offset from center coordinate
67- 72 F6.3 arcsec Ypos Y position offset from center coordinate
74- 78 F5.3 arcsec ePos Error in center coordinate position (1)
80- 85 F6.2 % a3/a ? 3rd cosine Fourier coefficient ratio (2)
87- 91 F5.2 % b3/a ? 3rd sine Fourier coefficient ratio (2)
93- 97 F5.2 % a4/a ? 4th cosine Fourier coefficient ratio (2)
99-103 F5.2 % b4/a ? 4th sine Fourier coefficient ratio (2)
105-109 F5.2 % a6/a ? 6th cosine Fourier coefficient ratio (2)
111-115 F5.2 % b6/a ? 6th sine Fourier coefficient ratio (2)
117-120 F4.2 --- Err Error in the Fourier coefficients (3)
--------------------------------------------------------------------------------
Note (1): Derived from the residual rms of the ellipse fit to the isophotes:
epos=rmsfit/(N0.5) with N≤128 the number of fitted points of
the isophote.
Note (2): Fourier coefficient (x100) describing the deviation of isophotal
shape from perfect ellipse.
Note (3): Defined as
Err=[(Σi=10N/2(ai2+bi2))/(N/2-10)]0.5*100/a.
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Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Name Galaxy name
10- 15 F6.2 arcsec Rad [-20.54/16.98] Radius
17- 22 F6.1 km/s vsini Stellar rotation velocity
24- 27 F4.1 km/s e_vsini Uncertainty in vsini
29- 33 F5.1 km/s sigma Velocity dispersion
35- 38 F4.1 km/s e_sigma Uncertainty in sigma
40- 45 F6.3 --- H3 Third order Gauss-Hermite moment
47- 51 F5.3 --- e_H3 Uncertainty in H3
53- 58 F6.3 --- H4 Fourth order Gauss-Hermite moment
60- 64 F5.3 --- e_H4 Uncertainty in H4
66- 68 I3 deg PA Position angle
70 I1 --- R Run number (G1)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table7.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Name Galaxy name
10- 15 F6.2 arcsec Rad [-18.86/20.09] Radius
17- 22 F6.1 km/s vsini Stellar rotation velocity
24- 27 F4.1 km/s e_vsini Uncertainty in vsini
29- 33 F5.1 km/s sigma Velocity dispersion
35- 39 F5.1 km/s e_sigma Uncertainty in sigma
41- 43 I3 deg PA Position angle
45 I1 --- R Run number
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table8.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Name Galaxy name
10- 15 F6.2 arcsec Rad [-20.54/16.98] Radius
17- 21 F5.3 0.1nm Hb ? The Hβ line-strength index; in Å
23- 27 F5.3 0.1nm e_Hb ? Uncertainty in Hb
29- 33 F5.3 0.1nm [MgFe] The [MgFe] line-strength index; in Å
35- 39 F5.3 0.1nm e_[MgFe] Uncertainty in [MgFe]
41- 45 F5.3 0.1nm <Fe> The <Fe> line-strength index; in Å
47- 51 F5.3 0.1nm e_<Fe> Uncertainty in <Fe>
53- 57 F5.3 0.1nm Mgb The Mgb line-strength index; in Å
59- 63 F5.3 0.1nm e_Mgb Uncertainty in Mgb
65- 69 F5.3 mag Mg2 The Mg2 line-strength index
71- 75 F5.3 mag e_Mg2 Uncertainty in Mg2
77- 79 I3 deg PA Position angle
81 I1 --- R Run number (G1)
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Global notes:
Note (G1): Run number as follows:
1 = Run 1 (wavelength range from 4670 to 6541Å) obtained on 2003 November
14-23 with the 2.4m Hiltner telescope of the MDM Observatory at Kitt Peak,
AZ. The telescope was mounted on the Moderate Resolution Spectrograph. The
"Echelle" CCD was adopted as detector.
2 = Run 2 (wavelength range from 4675 to 6530Å) obtained on 2005 October
25-31 with the 2.4m Hiltner telescope of the MDM Observatory at Kitt Peak,
AZ. The telescope was mounted on the Moderate Resolution Spectrograph. The
"Echelle" CCD was adopted as detector.
3 = Run 3 (wavelength range from 6270 to 7175Å) obtained on 2006 November
10-16 with the 2.4m Hiltner telescope of the MDM Observatory at Kitt Peak,
AZ. The Boller & Chivens CCD Spectrograph was mounted.
The "Ohio State University Loral C" CCD was the detector.
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 14-Oct-2013