Astronomy and Astrophysics, volume 611A, 28-28 (2018/3-1)
Hα imaging observations of early-type galaxies from the ATLAS3D survey.
GAVAZZI G., CONSOLANDI G., PEDRAGLIO S., FOSSATI M., FUMAGALLI M. and BOSELLI A.
Abstract (from CDS):
The traditional knowledge of the mechanisms that brought to the formation and evolution of early type galaxies (ETG) in a hierarchical Universe was challenged by the unexpected finding by ATLAS3D
that 86% ETGs show signs of a fast rotating disk at their interior, implying an origin common to most spiral galaxies, followed by a quenching phase, while only a minority of the most massive systems are slow rotators and were likely to be the products of merger events. Aims.
Our aim is to improve our knowledge on the content and distribution of ionised hydrogen and their usage to form stars in a representative sample of ETGs for which the kinematics and detailed morphological classification were known from ATLAS3D
Using narrow-band filters centered on the redshifted Hα line along with a broad-band (r-Gunn) filter to recover the stellar continuum, we observed or collected existing imaging observations for 147 ETG (including members of the Virgo cluster), representative of the whole ATLAS3D
55 ETGs (37%) were detected in the Hα line above our detection threshold (HαEW≤-1Å) and 21 harbour a strong source (HαEW≤-5Å) . Conclusions.
The strong Hα emitters appear associated with mostly low-mass (M*∼1010
) S0 galaxies which contain conspicuous stellar and gaseous disks, harbouring significant star formation at their interior, including their nuclei. The weak Hα emitters are almost one order of magnitude more massive, contain gas-poor disks and harbour an AGN at their centers. Their emissivity is dominated by [NII] and does not imply star formation. The 92 undetected ETGs constitute the majority in our sample and are gas-free systems which lack a disk and exhibit passive spectra even in their nuclei. These pieces of evidence reinforce the conclusion of Cappellari (2016ARA&A..54..597C
) that the evolution of ETGs followed the secular channel for the less massive systems and the dry merging channel for the most massive galaxies at the center of clusters of galaxies.
© ESO 2018
Galaxy: evolution - galaxies: - fundamental parameters - galaxies: star formation
VizieR on-line data:
<Available at CDS (J/A+A/611/A28): tablea1.dat tablea2.dat tablea3.dat tablea4.dat tablea5.dat tablea6.dat>
Paragraph. 4.1 Calibrator BD33 not identified, maybe BD +28 4211 from Massey et al. (1988).
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