Passive and star-forming galaxies at $1.4 \leq z \leq2.5$ in the Aegis field

Guanwen Fang; Xu Kong; Yang Chen; Xuanbin Lin

doi:10.1088/0004-637X/751/2/109

paper

Passive and star-forming galaxies at $1.4 \leq z \leq 2.5$ in the Aegis field

arXiv:1204.5354 · doi:10.1088/0004-637X/751/2/109

Abstract

Using a simple two-color selection based on $g$ -, $z$ -, and $K$ -band photometry, we pick out 1609 star-forming galaxies (sgzKs) and 422 passively evolving galaxies (pgzKs) at z\sim2 $f r o ma$ K $- ban d - se l ec t e d s am pl e ($ K_{\rm AB} < 22.0 $) inana r e a o f$ \sim 0.44 $d e g$ ^{2} $o f t h e A l l - w a v e l e n g t h E x t e n d e d G r o t h S t r i p I n t er na t i o na l S u r v ey . T h e n u mb er co u n t so f p g z K s in o u r s am pl e t u r n o v er a t$ K_{\rm AB} \sim 21.0 $, an d b o t h t h e n u mb er o f f ain t an d b r i g h t o bj ec t s (in c l u d in g s g z K s an d p g z K s) e x cee d t h e p r e d i c t i o n so f a r ece n t se mi - ana l y t i c m o d e l o f g a l a x y f or ma t i o n, am or es u ccess f u l m o d e l i s n ee d t oe x pl ain t hi s d i v er s i t y . W e a l so f in d t ha tt h es t a r f or ma t i o n r a t e (S F R) an d s p ec i f i c S F R (s S F R) o f s g z K s in cr e a ses w i t h r e d s hi f t a t a l l ma sses, im pl y in g t ha t s t a r - f or min g g a l a x i es w er e m u c hm or e a c t i v eo na v er a g e in t h e p a s t . M or eo v er, t h es S F R o f ma ss i v e g a l a x i es i s l o w er a t a l l r e d s hi f t s, s ug g es t in g t ha t s t a r f or ma t i o n co n t r ib u t es m or e t o t h e ma ss g r o w t h o f l o w - ma ss g a l a x i es t han t o hi g h - ma ss g a l a x i es . F r o m HubbleSpaceTelescope W i d e F i e l d C am er a 3 n e a r - in f r a r e d ima g in g d a t a, w e f in d t ha t m or p h o l o g i eso f$ z\sim2 $g a l a x i es n o t o n l y ha v e d i f f u ses t r u c t u r es w i t h l o w er$ G $an d hi g h er$ M_{20} $v a l u es, b u t a l so ha v es in g l e - o bj ec t m or p h o l o g i es (hi g h er$ G $an d l o w er$ M_{20} $), im pl y in g t ha tt h er e a r e m or p h o l o g i c a l v a r i e t y an dd i f f er e n t f or ma t i o n p r ocess f or t h ese g a l a x i es a t$ z\sim2 $. F ina l l y, w e a l sos t u d y t h e f r a c t i o n o f a c t i v e g a l a c t i c n u c l e i (A GN s) in t h e g z K s, 82 o f 828 g z K s w i t h f o u r I R A C ban d sc anb ec l a ss i f i e d a s A GN s ($ \sim $10$ L_{\rm 0.5-10\ keV}>10^{41}\,\rm erg\,s^{-1}$.

13 pages, 11 figures, accepted for publication in the Astrophysical Journal

Passive and star-forming galaxies at 1.4≤z≤2.5 in the Aegis field

Abstract

Passive and star-forming galaxies at $1.4 \leq z \leq 2.5$ in the Aegis field