VIMOS mosaic integral-field spectroscopy of the bulge and disk of the early-type galaxy NGC 4697
Date Issued
2015
Author(s)
•
L. Coccato
•
V. Pota
•
A. J. Romanowsky
•
G. Covone
•
M. Capaccioli
•
•
Description
The use of the Penalized Pixel Fitting developed by Cappellari and Emsellem is gratefully acknowledged. Data were reduced using EsoRex and XSH pipeline by ESO Data Flow System Group. CS thanks S. C. Trager for the use of the code SPINDEX2 and C. Conroy for the precious help in understanding and using his stellar population models. CT has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 267251. We thank the referee for very constructive comments.
Abstract
We present an integral field study of the internal structure, kinematics and
stellar population of the almost edge-on, intermediate luminosity ($L_ {*}$)
elliptical galaxy NGC 4697. We build extended 2-dimensional (2D) maps of the
stellar kinematics and line-strengths of the galaxy up to $\sim 0.7 $ effective
radii (R$_{eff}$) using a mosaic of 8 VIMOS (VIsible Multi-Objects Spectrograph
on the VLT) integral-field unit pointings. We find clear evidence for a
rotation-supported structure along the major axis from the 2D kinematical maps,
confirming the previous classification of this system as a `fast-rotator'. We
study the correlations between the third and fourth Gauss-Hermite moments of
the line-of-sight velocity distribution (LOSVD) $h_3$ and $h_4$ with the
rotation parameter ($V/\sigma$), and compare our findings to hydrodynamical
simulations. We find remarkable similarities to predictions from gas-rich
mergers. Based on photometry, we perform a bulge/disk decomposition and study
the stellar population properties of the two components. The bulge and the disk
show different stellar populations, with the stars in the bulge being older
(age$_{\rm bulge}=13.5^{+1.4}_{-1.4}$ Gyr, age$_{\rm
disk}=10.5^{+1.6}_{-2.0}$Gyr) and more metal-poor ($\mathrm{[M/H]_{bulge}} =
-0.17^{+0.12}_{-0.1}$, $\mathrm{[M/H]_{disk}}=-0.03^{+0.02}_{-0.1}$). The
evidence of a later-formed, more metal-rich disk embedded in an older, more
metal-poor bulge, together with the LOSVD structure, supports a mass assembly
scenario dominated by gas-rich minor mergers and possibly with a late gas-rich
major merger that left a previously rapidly rotating system unchanged. The
bulge and the disk do not show signs of different stellar Initial Mass Function
slopes, and both match well with a Milky Way-like IMF.
Volume
452
Issue
1
Start page
99
Issn Identifier
0035-8711
Ads BibCode
2015MNRAS.452...99S
Rights
open.access
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