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The homogeneous properties of Hα-selected galaxies at (0.05 < z < 0.15)


Kranz, W D; Tran, K V H; Giordano, L; Saintonge, A (2010). The homogeneous properties of Hα-selected galaxies at (0.05 < z < 0.15). Astronomical Journal, 140(2):561-576.

Abstract

We show that the Hα line (6563 Å) alone is an extremely effective criterion for identifying galaxies that are uniform in color (red), luminosity-weighted age (old), and morphology (bulge-dominated). By combining the Sloan Digital Sky Survey (Data Release 6) with the New York University Value-Added Galaxy Catalog, we have photometric and spectroscopic indices for over 180,000 galaxies at (0.05 < z < 0.15). We separate the galaxies into three samples: (1) galaxies with Hα equivalent width, EW <0 Å (i.e., no emission), (2) galaxies with morphological Sérsic index n > 2 (bulge-dominated), and (3) galaxies with n > 2 that are also red in (g' - r'). We find that the Hα-selected galaxies consistently have the smallest color scatter: for example, at z ~ 0.05 the intrinsic scatter in apparent (g' - r') for the Hα sample is only 0.0287 ± 0.0007 compared to 0.0682 ± 0.0014 for the Sérsic sample. Applying a color cut to the n > 2 sample does decrease the color scatter to 0.0313 ± 0.0007, but a measurable fraction of star-forming and/or active galactic nucleus galaxies (up to 9.3%) remain. All of the EW(Hα) <0 Å galaxies have n > 2, i.e., they are bulge-dominated systems. The spectra for the three samples confirm that the Hα-selected galaxies have the highest D4000 values and are, on average, nearly twice as old as the Sérsic-selected samples. With the advent of multi-object near-infrared spectrographs, Hα alone can be used to reliably isolate truly quiescent galaxies dominated by evolved stellar populations at any epoch from z ~ 0 up to z ~ 2.

We show that the Hα line (6563 Å) alone is an extremely effective criterion for identifying galaxies that are uniform in color (red), luminosity-weighted age (old), and morphology (bulge-dominated). By combining the Sloan Digital Sky Survey (Data Release 6) with the New York University Value-Added Galaxy Catalog, we have photometric and spectroscopic indices for over 180,000 galaxies at (0.05 < z < 0.15). We separate the galaxies into three samples: (1) galaxies with Hα equivalent width, EW <0 Å (i.e., no emission), (2) galaxies with morphological Sérsic index n > 2 (bulge-dominated), and (3) galaxies with n > 2 that are also red in (g' - r'). We find that the Hα-selected galaxies consistently have the smallest color scatter: for example, at z ~ 0.05 the intrinsic scatter in apparent (g' - r') for the Hα sample is only 0.0287 ± 0.0007 compared to 0.0682 ± 0.0014 for the Sérsic sample. Applying a color cut to the n > 2 sample does decrease the color scatter to 0.0313 ± 0.0007, but a measurable fraction of star-forming and/or active galactic nucleus galaxies (up to 9.3%) remain. All of the EW(Hα) <0 Å galaxies have n > 2, i.e., they are bulge-dominated systems. The spectra for the three samples confirm that the Hα-selected galaxies have the highest D4000 values and are, on average, nearly twice as old as the Sérsic-selected samples. With the advent of multi-object near-infrared spectrographs, Hα alone can be used to reliably isolate truly quiescent galaxies dominated by evolved stellar populations at any epoch from z ~ 0 up to z ~ 2.

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1 citation in Web of Science®
1 citation in Scopus®
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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute for Computational Science
Dewey Decimal Classification:530 Physics
Language:English
Date:August 2010
Deposited On:03 Mar 2011 15:35
Last Modified:05 Apr 2016 14:33
Publisher:Institute of Physics Publishing
ISSN:0004-6256
Publisher DOI:10.1088/0004-6256/140/2/561
Related URLs:http://arxiv.org/abs/1006.2831
Permanent URL: http://doi.org/10.5167/uzh-41826

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