ON THE RADIAL STELLAR CONTENT OF EARLY-TYPE GALAXIES AS A FUNCTION OF MASS AND ENVIRONMENT

Journal Article · Thu Oct 20 04:00:00 EDT 2011 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/740/2/L41· OSTI ID:21565369

La Barbera, F ^[1]; Ferreras, I ^[2]; De Carvalho, R R ^[3]; Lopes, P A. A. ^[4]; Pasquali, A ^[5]; De la Rosa, I G ^[6]; De Lucia, G ^[7]

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1. INAF-Osservatorio Astronomico di Capodimonte, Napoli (Italy)
2. MSSL, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT (United Kingdom)
3. Instituto Nacional de Pesquisas Espaciais/MCT, S. J. dos Campos (Brazil)
4. Observatorio do Valongo/UFRJ, Rio de Janeiro (Brazil)
5. Astronomisches Rechen Institut, Zentrum fuer Astronomie der Universitaet Heidelberg, Moenchhofstr. 12-14, 69120 Heidelberg (Germany)
6. Instituto de Astrofisica de Canarias (IAC), E-38200 La Laguna, Tenerife (Spain)
7. INAF-Osservatorio Astronomico di Trieste, via G.B. Tiepolo 11, 1-34143 Triste (Italy)

Using optical-optical and optical-NIR colors, we analyze the radial dependence of age and metallicity inside massive (M{sub *} {approx}> 10{sup 10.5} M{sub sun}), low-redshift (z < 0.1), early-type galaxies (ETGs), residing in both high-density group regions and the field. On average, internal color gradients of ETGs are mainly driven by metallicity, consistent with previous studies. However, we find that group galaxies feature positive age gradients, {nabla} {sub t}, i.e., a younger stellar population in the galaxy center, and steeper metallicity gradients, compared to the field sample, whose {nabla} {sub t} ranges from negative in lower mass galaxies to positive gradients at higher mass. These dependencies yield new constraints on models of galaxy formation and evolution. We speculate that age and metallicity gradients of group ETGs result from (either gas-rich or minor-dry) mergers and/or cold-gas accretion, while field ETGs exhibit the characteristic flatter gradients expected from younger, more metal-rich stars formed inside-out by later gas cooling.

• OSTI ID: 21565369
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 2 Vol. 740; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
COLOR
COOLING
ELEMENTS
EVOLUTION
GALACTIC EVOLUTION
GALAXIES
GALAXY CLUSTERS
GAS COOLING
MASS
METALS
OPTICAL PROPERTIES
ORGANOLEPTIC PROPERTIES
PHYSICAL PROPERTIES