Minor Galaxy Interactions: Star Formation Rates and Galaxy Properties

Deborah Freedman Woods; Margaret J. Geller

doi:10.1086/519381

paper

Minor Galaxy Interactions: Star Formation Rates and Galaxy Properties

arXiv:astro-ph/0703729 · doi:10.1086/519381

Abstract

We study star formation in a sample of 1204 galaxies in minor (| Δm_z | \geq 2) pairs and compact groups, drawn from the Sloan Digital Sky Survey Data Release 5 (SDSS DR5). We analyze an analogous sample of 2409 galaxies in major (| Δm_z | < 2 $) p ai r s an d co m p a c t g r o u p s t oe n s u r e t ha t o u r se l ec t i o n r e p r o d u ces p r e v i o u sr es u l t s, an d w e u se a ‘‘ f i e l d^{''} s am pl eo f 65, 570 g a l a x i es f or co m p a r i so n . O u r maj or an d min or p ai r ss am pl es in c l u d eo n l y g a l a x i es in s p ec t r osco p i c a l l y co n f i r m e d p ai r s, w h er e t h er ecess i o na l v e l oc i t y se p a r a t i o n$ ΔV < 500 $k m / s an d t h e p r o j ec t e d s p a t ia l se p a r a t i o n$ ΔD < 50 $k p c / h . T h er e l a t i v e ma g ni t u d e (a p r o x y f or t h e ma ssr a t i o) o f t h e p ai r i s anim p or t an tp a r am e t er in t h ee f f ec t i v e n esso f t h e t i d a l l y t r i g g er e d s t a r f or ma t i o ninmin or in t er a c t i o n s . A se x p ec t e d, t h eseco n d a r y g a l a x i es inmin or p ai r ss h o w e v i d e n ce f or t i d a l l y t r i g g er e d s t a r f or ma t i o n, w h er e a s t h e p r ima r y g a l a x i es in t h e min or p ai r s d o n o t . T h e g a l a x y co l or i s a l so anim p or t an tp a r am e t er in t h ee f f ec t i v e n esso f t r i g g er e d s t a r f or ma t i o nin t h e maj or g a l a x y p ai r s . I n t h e maj or p ai r ss am pl e, t h er e i s a cor r e l a t i o nb e tw ee n t h es p ec i f i cH$ α $s t a r f or ma t i o n r a t e (S S F R) an d$ ΔD$ in the blue primary and blue secondary galaxies; for the red primary and red secondary galaxies, there is none. Galaxies in pairs have a higher mean SSFR at every absolute magnitude compared to matched sets of field galaxies, and the relative increase in mean SSFR becomes larger with decreasing intrinsic luminosity. We also detect a significantly increased AGN fraction in the pair galaxies compared to matched sets of field galaxies.

29 pages, 31 figures, submitted to AJ

Minor Galaxy Interactions: Star Formation Rates and Galaxy Properties

Abstract

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