The origin of EA galaxies Tomo Goto Japan

The origin of E+A galaxies Tomo Goto Japan Aerospace Exploration Agency Tomo Goto 1

January In Japan In Chile Tomo Goto

The origin of E+A galaxies Strong Balmer absorption No [OII], no Hα ÞPost-starburst A star + absorption lines ÞE+A galaxies ÞK+A galaxies Tomo Goto Japan Aerospace Exploration Agency Tomo Goto 3

Two puzzles on E+A(post-starburst) What caused star burst? What stopped it? n n n Cluster related. Found to live in cluster region (MORPHS, Dressler & Gunn 83) Dust enshrouded star formation. (Poggianti et al. 1999; Smail et al. 1999) Merger/Interaction (Zabludoff et al 1996) 　 n n Still puzzles Very rare(21/11113 in LCRS). Phase is short(1 Gyr). Million spectra of SDSS provide good opportunity to address this 20 -year-old puzzle. Galaxy evolution in action. Tomo Goto 4

Tomo Goto

color morphology Morphological Butcher-Oemler effect in CE (Goto, et al. 2003, PASJ, 55, 755) More blue galaxies in higher redshift The Morphological BO Effect Tomo Goto 6

Sloan Digital Sky Survey (SDSS) n SDSS will produce u Imaging of 10, 000 sq. deg r~23. 1 In 5 optical bands (ugriz) u Spectra of and in 5 years Using 2. 5 m telescope at APO. Tomo Goto 7

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Evolution is difficult to observe. Elliptical Galaxy@z=0 Important Transition Stage pop. III galaxy@z=10 ? Spiral galaxy@z=0 It is important to observe galaxy evolution in action. => E+As Tomo Goto 10

n Not much information on past SFH Tomo Goto Truncation of SF: galaxy evolution in action n 11

How to find E+As Goto, T. et al. 2003, PASJ, 55, 771 Goto, T. 2005, MNRAS, 357, 937 n n HδEW>4Å (2. 42%) 4 categories. • E+A: Hα<1σ, [OII]<1σ, No emission lines. (0. 04%) • HDS+[OII]: Hα<1σ, [OII]≧ 1σ (0. 09%) • HDS+Hα: Hα≧ 1σ, [OII]<1σ (0. 04%) • HDS+em: Hα≧ 1σ, [OII]≧ 1σ, Significant emission lines. (2. 25%) The largest catalog of 564 E+As out of 650, 000 galaxies. Tomo Goto 12

E+A Spectra Tomo Goto 13

E+A Atlas Images Tomo Goto 14

HDS+em Spectra Tomo Goto 15

HDS+em Sample Atlas Images Tomo Goto 16

HDS+Hα Spectra n n n [OII] has been used as SF indicator. Could be dust? Metallicity effect? 　 Possible 52% contamination in high-z work Tomo Goto 17

HDS+Hα Atlas Images Tomo Goto 18

HDS+[OII] Spectra • Could be self-absorption? • HI gas cloud? Tomo Goto 19

HDS+[OII] Atlas Images Tomo Goto 20

Three Scenarios for E+A 1. Cluster Related (ram pressure, tidal interaction with cluster potential, …etc; Dressler et al. 1999; Poggianti et al. 1999) 2. Dusty Starburst (2/15 of E+As have radio SF; Miller et al. 2002; Smail et 3. Interaction/Merger (tidal features in 5/21 E+As in Zabludoff et al. 1996) al. 1997; ) Tomo Goto 21

E+A is K+A E+A “E+A” is sometime called “K+A” because of its disklike morphology. However, … Previous sample might be contaminated by HDS+Hα Tomo Goto 22

Environment of E+A Galaxies Goto, T. 2005, MNRAS, 357, 937 Not by cluster, not by large-scale structure Tomo Goto 23

Three Scenarios for E+A 1. Cluster related (ram pressure, tidal interaction, merging…etc; Dressler et al. 1999; Poggianti et al. 1999) 2. Dusty Starburst (2/15 of E+As have radio SF; Miller et al. 2002; Smail et al. 1997; ) 3. Interaction/Merger (tidal features in 5/21 E+As in Zabludoff et al. 1996) Tomo Goto 24

Optical-Infrared color: r-K E+As are not dustier. (c. f. , 5 dusty starbursts in Smail et al. are ~1 mag redder. ) Tomo Goto 25

Radio Estimated SFR Goto, T. 2004, A&A, 427, 125 No evidence that E+As are not dusty starbursts. Tomo Goto 26

Three Scenarios for E+A 1. Cluster related (ram pressure, tidal interaction, merging…etc; Dressler et al. 1999; Poggianti et al. 1999) 2. Dusty Starburst (2/15 of E+As have radio SF; Miller et al. 2002; Smail et al. 1997; ) 3. Interaction/Merger (tidal features in 5/21 E+As in Zabludoff et al. 1996) Tomo Goto 27

Hδ_EW vs Time Tomo Goto 28

u-g vs HδEW (current SF vs recent SF) Young E+As: closer to burst (130 -470 Myrs) Tomo Goto 29

Young E+A Spectra (HδEW>7Å) Tomo Goto 30

Atlas Image of Young E+As Tomo Goto 31

Naccompanying galaxies More accompanying galaxies for young E+As at <100 kpc scale. Goto, T. 2005, MNRAS, 357, 937 Tomo Goto 32

Three Scenarios for E+A 1. Cluster related (ram pressure, tidal interaction, merging…etc; Dressler et al. 1999; Poggianti et al. 1999) 2. Dusty Starburst (2/15 of E+As have radio SF; Miller et al. 2002; Smail et al. 1997; ) 3. Interaction/Merger (tidal features in 5/21 E+As in Zabludoff et al. 1996) Tomo Goto 33

178 Ultra Luminous Infrared Galaxy (ULIRG) 1012 Lsun< Lir<1013 Lsun Largest Sample of ULIRG before ASTROF Goto, T. 2005, MNRAS, 360, 322 Tomo Goto 34

Not every meger is E+A. Goto, T. 2005, MNRAS, 360, 322 Tomo Goto 35

color morphology Morphological Butcher-Oemler effect in CE (Goto, et al. 2003, PASJ, 55, 755) More blue galaxies in higher redshift The Morphological BO Effect Tomo Goto 41

Passive Spiral Galaxies in the SDSS (Goto et al. 2003, PASJ, 55, 757) Spiral but no star formation. What are these? Tomo Goto 42

Optical-IR color --- not dustier PS do not look like dusty star forming galaxies. Yamauchi & Goto 2004 MNRAS, 352, 815 Tomo Goto 43

The Environment of Passive Spirals (Goto et al. 2003, PASJ, 55, 757) Passive spirals may be a smoking gun in cluster galaxy evolution. Tomo Goto 44

Morphology Radius Relation (Goto et al. 2003, MNRAS, 346, 601, ) SFR : Gomez et al. 2003 Tomo Goto 45

The Origin of E+As ü E+As are in all environment including the field. èE+As are not cluster/LSS origin. ü Optical-IR color is not redder; radio SFR<10 Msun/yr. èE+As are not likely to be Dusty Starburst. ü Excess in Naccompanying galaxies. èMerger/interaction is most likely to be responsible for the E+As. Consistent with E morphology. Tomo Goto 48