Hostname: page-component-848d4c4894-89wxm Total loading time: 0 Render date: 2024-07-07T14:39:30.306Z Has data issue: false hasContentIssue false

Star Formation History of Early-Type Galaxies with Tidal Debris in the S4G

Published online by Cambridge University Press:  05 March 2015

Beatriz H. F. Ramos
Affiliation:
Instituto de Biociências, Departamento de Ciências Naturais, Universidade Federal do Estado do Rio de Janeiro, Rio de Janeiro, Brazil email: ramos@astro.ufrj.br Observatório do Valongo, Universidade Federal de Rio de Janeiro, Rio de Janeiro, Brazil
Karín Menéndez-Delmestre
Affiliation:
Observatório do Valongo, Universidade Federal de Rio de Janeiro, Rio de Janeiro, Brazil
Taehyun Kim
Affiliation:
European Southern Observatory, Santiago, Chile Dept. Physics & Astronomy, Seoul National University, Seoul, Republic of Korea
Kartik Sheth
Affiliation:
National Radio Astronomy Observatory, Charlottesville, VA, USA
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Local early-type galaxies (ETGs), despite typically being associated to old stellar populations and passive evolution, have been in some cases observed to present peculiarities in their stellar structure, like disks and shells (e.g., Kormendy et al.1997, Rix, Carollo & Freeman 1999). Moreover, it has been observed that ETGs with such tidal features may present UV emission (Rampazzo et al.2007, Salim & Rich 2010). These properties make them relevant constraints to galaxy formation models. We are analysing the structure of nearby ETGs observed in the Spitzer Survey of Stellar Structure in Galaxies (S4G; Sheth et al.2010), which comprises the largest mid-IR survey of galaxies in the local Universe. We perform a 2D GALFIT decomposition of the 3.6μm images of 146 ETGs and examine their residual images. We identify tidal features in 17% of these, suggesting that a non-negligible ETGs fraction may have experienced (after the formation of the bulk of their stellar budget) merger events that have left signatures (Canalizo et al.2007). For 6 of these peculiar ETGs, we also applied GALFIT decomposition to public GALEX/UV and SDSS/optical images. With measurements in multiple bands, we applied SED fitting techniques to estimate star formation rates (SFR) and stellar masses for the galaxies and their tidal features. We find that these 6 peculiar ETGs present masses in agreement with the population of non-peculiar ETGs. However, SFRs are higher than what has been measured for the average ETG population (Shapiro et al.2010, SDSS MPA-JHU catalog). Based on the Kaviraj (2010) relation, we find that for these peculiar ETGs the estimated age of the most recent star formation event is less than 3Gyrs. Despite this indication of recent star formation, we have not found evidence of prominent UV emission in the tidal features (Marino et al.2010). We are currently extending our work to the full sample of peculiar ETGs identified in our sample.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2015 

References

Canalizo, G., et al. 2007, ApJ 669, 801CrossRefGoogle Scholar
Kaviraj, S. 2010, MNRAS 408, 170Google Scholar
Kormendy, J., et al. 1997, ApJ 482, L139Google Scholar
Marino, A., et al. 2011, MNRAS 411, 311CrossRefGoogle Scholar
Rampazzo, R., et al. 2007, MNRAS 381, 245Google Scholar
Rix, H.-W., Carollo, C. M., & Freeman, K. 1999, ApJ 513, L25Google Scholar
Salim, S. & Rich, R. M. 2010, ApJ 714, L290Google Scholar
Shapiro, K. L., et al. 2010, MNRAS 402, 2140CrossRefGoogle Scholar
Sheth, K., et al. 2010, PASP 122, 1397CrossRefGoogle Scholar