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Date and Time of the Query: 2019-06-24 T11:31:55 PDT
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For refcode 2005A&A...433..497R:
Retrieve 50 NED objects in this reference.
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NED Abstract

Copyright by European Southern Observatory (ESO). Reproduced by permission
2005A&A...433..497R Nearby early-type galaxies with ionized gas I. Line-strength indices of the underlying stellar population R. Rampazzo, F. Annibali, A. Bressan, M. Longhetti, F. Padoan and W. W. Zeilinger Received 28 January 2003 / Accepted 1 December 2004 With the aim of building a data-set of spectral propertiesof well studied early-type galaxies showing emission lines, we present intermediate resolution spectra of 50 galaxies in the nearby Universe. The sample, which covers several of the E and S0 morphologicalsub-classes, is biased toward objects that might be expected to have ongoing and recent star formation, at least in small amounts, because of the presenceof the emission lines. The emission is expected to come from the combinationof active galactic nuclei and star formation regions within the galaxies. Sample galaxies are located in environments corresponding to a broad range of local galaxy densities, although predominantly in low density environments. Our long-slit spectra cover the 3700-7250 {Angstrom} wavelength range with aspectral resolution of ~7.6 {Angstrom} at 5550 {Angstrom}. The specific aim of this paper, and our first step in the investigation, is to map the underlying galaxy stellar population by measuring, along the slit positioned along the galaxy major axis, line-strength indices at several, homogeneous galacto-centric distances. For each object we extracted 7 luminosity-weighted apertures (with radii 1.5, 2.5, 10, r_e_/10, r_e_/8, r_e_/4 and r_e_/2) corrected for the galaxy ellipticity and 4 gradients (0 <=q r <=q r_e_/16, r_e_/16 <=q r <=q r_e_/8, r_e_/8 <=q r <=q r_e_/4 and r_e_/4 <=q r <=q r_e_/2). For each aperture and gradient we measured 25 line-strength indices: 21 of the set defined by the Lick-IDS "standard" system (Trager et al. 1998, ApJS, 116, 1) and 4 introduced by Worthey & Ottaviani (1997, ApJS, 111, 377). Line-strength indices have been transformed to the Lick-IDS system. Indices derived then include H{beta}, Mg_1_, Mg_2_, Mgb, MgFe, Fe5270, Fe5335 commonly used in classic index-index diagrams. The paper introduces the sample, presents the observations, describes the data reduction procedures, the extraction of apertures andgradients, the determination and correction of the line-strength indices, the procedure adopted to transform them into the Lick-IDS System and the procedures adopted for the emission correction. We finally discuss the comparisons between our dataset and line-strength indices available in the literature. A significant fraction, about 60%, of galaxies in the present sample has one previous measurement in the Lick-IDS system but basically restricted within the r_e_/8 region. Line-strength measures obtained both from apertures and gradients outside this area and within ther_e_/8 region, with the present radial mapping, are completely new. Keywords: galaxies: elliptical and lenticular, cD, galaxies: fundamental parameters, galaxies: formation, galaxies: evolution
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