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Post Info TOPIC: Early-type Galaxies
Blobrana


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RE: Early-type Galaxies
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Title: Ultraviolet colour-colour relation of early-type galaxies at 0.05 < z < 0.12
Authors: Chang H. Ree (1), Hyunjin Jeong (1,2), Kyuseok Oh (2), Chul Chung (2), Joon Hyeop Lee (1), Sang Chul Kim (1), Jaemann Kyeong (1) ((1) Korea Astronomy and Space Science Institute, (2) Department of Astronomy, Yonsei University)

We present the ultraviolet (UV) colour-colour relation of early-type galaxies (ETGs) in the nearby universe (0.05 < z < 0.12) to investigate the properties of hot stellar populations responsible for the UV excess (UVX). The initial sample of ETGs is selected by the spectroscopic redshift and the morphology parameter from the Sloan Digital Sky Survey (SDSS) DR7, and then cross-matched with the Galaxy Evolution Explorer (GALEX) Far-UV (FUV) and Near-UV (NUV) GR6 data. The cross-matched ETG sample is further classified by their emission line characteristics in the optical spectra into quiescent, star-forming, and AGN categories. Contaminations from early-type spiral galaxies, mergers, and morphologically disturbed galaxies are removed by visual inspection. By drawing the FUV - NUV (as a measure of UV spectral shape) vs. FUV - r (as a measure of UVX strength) diagram for the final sample of ~3700 quiescent ETGs, we find that the "old and dead" ETGs consist of a well-defined sequence in UV colours, the "UV red sequence", so that the stronger UVX galaxies should have a harder UV spectral shape systematically. However, the observed UV spectral slope is too steep to be reproduced by the canonical stellar population models in which the UV flux is mainly controlled by age or metallicity parameters. Moreover, 2 mag of colour spreads both in FUV - NUV and FUV - r appear to be ubiquitous among any subsets in distance or luminosity. This implies that the UVX in ETGs could be driven by yet another parameter which might be even more influential than age or metallicity.

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Blobrana


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Posts: 131433
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Title: Towards a New Classification of Early-type Galaxies: An Integral-field View.
Authors: Falcon-Barroso, J. Bacon, R. Cappellari, M. Davies, R.L. de Zeeuw, P.T. Emsellem, E. Krajnovic, D. Kuntschner, H. McDermid, R.M. Peletier, R.F. Sarzi, M. van de Ven, G.
(2008)

In this proceedings paper we make use of the two-dimensional stel- lar kinematics of a representative sample of E and S0 galaxies obtained with the SAURON integral-field spectrograph to reveal that early-type galaxies appear in two broad flavours, depending on whether they exhibit clear large-scale rotation or not. We measure the level of rotation via a new parameter (R) and use it as a basis for a new kinematic classification that separates early-type galaxies into slow and fast rotators. With the aid of broad-band imaging we will reinforce this finding by comparing our kinematic results to the photometric properties of these two classes.

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Blobrana


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Posts: 131433
Date:
Chemical enrichment of early type galaxies
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Title: Stellar mass-loss, rotation and the chemical enrichment of early type galaxies
Authors: Antonio Pipino (USC), Cristina Chiappini (Geneve/INAF-Trieste), Genevieve Graves (UCSC), Francesca Matteucci (Dip. Astronomia, Univ. Trieste)

We present a comparison between the [Ca,C,N/Fe]-mass relations observed in local spheroids and the results of a chemical evolution model which already successfully reproduces the [Mg/Fe]-mass and the [Fe/H]-mass relations in these systems. We find that the [Ca/Fe]-mass relation is naturally explained by such a model without any additional assumption. In particular, the observed under-abundance of Ca with respect to Mg can be attributed to the different contributions from supernovae Type Ia and supernovae Type II to the nucleosynthesis of these two elements. For C and N, we consider new stellar yields that take into account stellar mass loss and rotation. These yields have been shown to successfully reproduce the C and N abundances in Milky Way metal-poor stars. The use of these new stellar yields produces a good agreement between the chemical evolution model predictions and the integrated stellar population observations for C. In the case of N, the inclusion of fast rotators and stellar mass-loss nucleosynthesis prescriptions improves our predictions for the slope of the [N/Fe] vs. sigma relation, but a zero point discrepancy of 0.3 dex remains. This work demonstrates that current stellar yields are unable to simultaneously reproduce the large mean stellar [<N/Fe>] ratios inferred from integrated spectra of elliptical galaxies and the low N abundance measured in the gas of high redshift spheroids from absorption lines. However, it seems reasonable to suggest that there may be uncertainties in either the inferred stellar or gas-phase N abundances at the level of 0.3 dex.

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Blobrana


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Posts: 131433
Date:
Early-type Galaxies
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Title: Chandra Observations of Early-type Galaxies
Authors: Alex E Athey

We have performed uniform analysis of a sample of 54 nearby, early-type galaxies observed with Chandra. In this work we present the spectral results for both the diffuse Interstellar Medium, ISM, and low-mass X-ray binaries, LMXBs. We determine the metallicity of the hot ISM in the 22 brightest galaxies and find a narrow range of abundance ratios relative to iron. The average iron metallicity of these bright galaxies is 0.96 ±0.33 relative to solar. By assuming these enrichment patterns continue to fainter galaxies, we are able to extend accurate ISM modelling down to the faintest galaxies in the sample. The sample of galaxies span 4.5 orders of magnitude in X-ray luminosity starting at L_X=10^{38} erg \cdot s^{-1} and the average gas temperature in the sample is 0.58 ±0.24 keV. We present the X-ray properties of these galaxies scaled to one effective radius as well as radial variations of gas and stellar binary luminosities, and radial variations of gas temperature, metallicity, mass, entropy and density.

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