Star formation histories and environment Bianca M. Poggianti INAF – Osservatorio Astronomico di Padova WE ARE ALL AFTER THE BIG PICTURE: 1)To what extent, environment To what extent intrinsic/galaxy mass or else 2) When environment, what physical mechanism (hence, where & when)

Dressler 1980, as in Dressler et al MORPHOLOGY-DENSITY RELATION in clusters projected surface density (log) Fraction of galaxies E Spirals S0 How to measure environment? One way is to measure the local galaxy density Number of neighbours, brighter than a certain mag limit, per unit of projected area or volume Observationally rather easy, even with just photometry –

Another way is to measure the mass of the host structure (cluster and group) Cluster velocity dispersion X-ray luminosity Cluster total luminosity/richness Weak-lensing Sunyaev-Zeldovich… Popesso et al Optical luminosity Virial mass X-ray luminosity Limitation of general field studies until recently: dont discriminate environment (groups/isolated) – so the evolution in the field could be driven by the growth of structure (environment) - now starting (DEEP2, zCOSMOS etc) Location in a cluster, group, filament, void In clusters, clustercentric distance (with respect to virial or stripping radius), substructure etc ….usefulness of single, very well studies cases where physics becomes evident

OUTLINE StarFormation and Local Density StarFormation and Cluster/Group Mass Evolution of the StarFormation in Clusters (red sequence, blue/emission line galaxies, post- starburst galaxies) Star Formation and Galaxy Morphology the big picture (?)

IMPORTANT TO ASK TWO SEPARATE QUESTIONS: a)The fraction of star-forming (or passive) galaxies: Often this is done checking blue vs red fraction: Butcher-Oemler effect ---- red sequence build-up Quantify the evolution of red% as a function of environment b) SFR in SFing galaxies depends on environment? If not, either changes are intrinsic (NOT-environmentally driven) OR changes are abrupt/fast

The evolution of the star formation-density relation

Low-z SDSS Baldry et al Bundy et al DEEP2 + Simon Lillys talk zCOSMOS and posters Log M (stellar mass) Mass fraction per dex Galaxy stellar mass function itself varies with density

SDSS Baldry et al. 2006, also Kauffmann et al Red galaxy fraction depends on both local density and galaxy stellar mass Low redshift Local density Galaxy mass

The red galaxy fraction-density relation at higher-z DEEP2 Cooper et al. 2007, Gerke et al VVDS Cucciati et al Galaxies turning from blue to red preferentially in overdense regions (groups??) at z below 1.5 – the establishment of the SFing fraction-density relation at z = ? (More massive environments, higher-z – clusters are the tail of a distribution…) 0.4<z< <z< <z<1.01.0<z<1.3

Low redshift Halpha equivalent width Fraction of galaxies Balogh et al. 2004a So, the SF-ing % depends on density. The SF in SF-ing galaxies doesnt ?

COSMOS Cassata et al – also Noeskes 2007 Letters WHAT CHANGES WITH ENVIROMENT IS ONLY THE STARFORMING FRACTION (higher-z)? Color-mass diagram, at different local densities Z~ 0.7

Black z= (ESO Distant Cluster Survey) Red z= (SDSS clusters) Poggianti et al Star-forming fraction Local density Mean(EW) of OII galaxies Local density STAR FORMATION-LOCAL DENSITY RELATION Clusters at z=0 & ?

Average SFR per galaxy vs density: field at z=1 Elbaz et al Cooper et al The relation between the average star formation rate per galaxy and the local density is reversed compared to the local Universe. (is it?) Z=0 Z=1 And for just star-forming galaxies? With same mass distributions? higher density

ESO Distant Cluster Survey Poggianti et al All galaxies (black) SFing galaxies (blue) Clusters + groups at z~ Average SFR vs density (sSFR same way) Seems to imply the SFR in SF-ing galaxies depends on density – while the EW-density relation seems to imply it doesnt

The evolution of the star formation activity as a function of cluster/group mass

The oldest galaxies at any redshift Color-Magnitude sequence: zero-point, slope and scatter consistent with passive evolution of stellar populations formed at z>2-3 (Bower, Ellis, Kodama…). Fundamental plane, mass-to-light ratios and Mg-sigma relation, bright-end of K-band (mass) luminosity function Z = 1.24 ACS team Z= Mei et al. 2008

STAR FORMATION DOWNSIZING: the cluster view 0.0 redshift 1 Red sequence faint-to-luminous ratio De Lucia et al. 2004, 2007, Kodama et al. 2004, Stott et al. 2007, Tanaka et al. 2005, but Andreon 2008 A deficiency of red galaxies at faint magnitudes in distant clusters compared to nearby clusters. Most massive galaxies are the first ones to conclude their SF activity - The more massive, the older their stellar populations,and the higher the redshift of their last SF V absolute magnitude U-V color Kodamas talk

STAR FORMING FRACTION vs z IN CLUSTERS Spectroscopy confirmed a widespread SF activity in z= clusters: Star-forming fraction 30-50%, compared to nearby similar clusters that contain few galaxies with ongoing or recent SF Fraction of blue galaxies versus redshift Butcher-Oemler 1984, Kodama & Bower 2001 Dressler & Gunn 1982, 1983, Couch & Sharples 1987, Poggianti et al. 1999, Dressler et al. 1999, Ellingson et al. 2001, Balogh et al. 1997…. 0.0 z 0.5

Trends with cluster/group mass: low-z Richer, more centrally concentrated, relaxed clusters have fewer star-forming/late-type galaxies. Early attempts with (e.g. Zabludoff & Mulchaey 1998, Biviano et al. 1997) and without (e.g. Smail et al. 1998, Andreon & Ettori 1999) success. But hard to quantify: Fractions of galaxy types versus system mass (vel.dispersion) Weinmann et al log M

Balogh et al Red galaxy % vs sigma Goto 2005 – also Tanaka et al Blue galaxy % vs sigma Trends with system mass at low-z II

Evolution of the % of SF-ing galaxies EDisCS z = Sloan z = Fraction of members with OII within R200 Velocity dispersion ESO Distant Cluster Survey Poggianti et al OUTLIERS!

Evolution of the star-forming fraction Change in star-forming fraction between 20 and 50% - stronger in lower mass systems How are these trends established? Note that the low-z trend HAD break at some sigma, otherwise the field today would be like the clusters/groups. A universal 3 X 10^12 halo mass threshold for quenching (within 3Gyr from infall) produces far too few starforming galaxies in clusters of any sigma today! Poggianti et al. 2006

How do galaxies turn from star-forming to passive in clusters, and why: well studied, individual clusters Evidence forenhancement slow decline sudden truncation Moran et al. 2005, 2006, 2007a,b,c Small bursts at virial radius Slow conversion of spirals to S0s in infalling groups in the outskirts (gentle gal.-gal. Interactions?) + additional fast truncation mechanism in inner regions (ram pressure? where ICM dense) Harassment, ram pressure and starvation? Cl0024 and MS0451 at z=0.4 starvationtruncation

A quenching timescale dependent on galaxy mass… STAGES Wolf et al Also Haines et al. 2006, 2007 Dusty red galaxies: logM=[10-11], low mean specific star formation rate (dust reddened), indicating quenching is slow – (see also Goto et al. 2003) – but could it be just that are more massive are earlier-type galaxies? In lower mass galaxies, fast quenching accompanied by morphological change (no cluster-specific red spirals phenomenon at logM<10) logMass Log SFR/M

If a truncation mechanism acts fast, it leaves a clear signature…. post-starburst galaxies

POST-STARBURST SPECTRA IN DISTANT CLUSTERS (z= ) post-starburst galaxies 25% of the distant cluster galaxy population Dressler & Gunn 1983, Couch & Sharples 1987, Dressler et al. 1999, Poggianti et al. 1999, Tran et al. 2001, 2004 Larger % in clusters than in field at similar zs (Dressler et al. 1999, Poggianti et al. 1999, Tran et al. 2003,2004, now Ediscs, Ma et al… – but Balogh et al. 1999) SF truncation in clusters strong Balmer absorption and no line detected in emission SF ended abruptly sometime during the last Gyr

EDisCS Poggianti et al At z= , post-starburst galaxies more frequent in more massive clusters and in some of the groups… …those groups with a low OII fraction for their sigma K+a fraction

Post-starburst downsizing in clusters In the Coma cluster – Rare among bright galaxies, but common (15%) among dwarfs (Poggianti et al. 2004) Evidence for ICM origin: In Coma, associated with X-ray substructure, pointing to impact with ICM shock fronts (Poggianti et al. 2004). In cluster at z=0.5, post-starbursts within the (projected) ram pressure stripping radius (Ma et al. 2008) M v - 18

Post-starburst fractions among bright field galaxies In the field at z=0, mostly associated with mergers (Zabludoff et al. 1996, Yang et al. 2004, 2008, Goto 2005, Nolan et al. 2007). Confirmed by spectroscopy of companions (Goto 2005, Yamauchi et al. 2008, also Goto et al. 2008) Highly probable different origin in different environments Rare at all redshifts (Zabludoff et al. 1996, Goto 2005, Yan et al. 2009) AGN and SN feedback above/below 10^10 Msun – descendants of LIRGs and ULIRGs (Kaviraj et al. 07) Evolution of frequency also in the field: a factor of 230 between 0.07 and 0.7 (Wild et al. 2009) How relevant for the evolution of the star-forming fraction and of the cosmic SF history? Open question (eg Yan et al vs Wild et al – 40% of red sequence growth rate)

GROUP BIMODALITY ? THE KEY? Evidence: some groups look like mini-clusters, some look like field (at the same mass) for their star forming fraction, morphologies, post- starburst incidence etc Poggianti et al. 2006, 2008, 2009a, Wilman et al. 2005, 2009, Kautsch et al. 2008, Jeltema et al – also Zabludoff & Mulchaey 1998…. Not simply true vs false groups? (eg. X-ray groups Jeltema et al Rasmussens talk) – hard to explain as wrong mass estimate Difference between two types of groups ought to help to understand what is going on at the group level

Fritz et al. In prep. Red sequence build-up from secular SF histories Irr Sd Sc Sb Sa S0 E Log stellar mass (Msun)

Star formation and galaxy morphology (Hubble type)

Desai et al. (2007) (Dressler et al. 1997, Fasano et al. 2000, Postman et al. 2005, Smith et al – but also Andreon et al. 1998, Holden et al. 2009) MORPHOLOGICAL EVOLUTION IN CLUSTERS: from spiral to S0 GALAXIES Elliptical % S0 % Spiral+Irr %

Wide-field Nearby Galaxy-cluster Survey (WINGS) Poggianti et al ApJ Letter Evolution of the morphological fractions AGAIN, EVOLUTION IS STRONGER IN LESS MASSIVE CLUSTERS!! also Wilmans talk, Kautsch et al for S0s in groups (and Dressler 1980…) Also Dennis Justs poster

WINGSdatabase Wide Field (35, R500 in all) Sample: 76 clusters, complete in L X ; 0.04<z<0.07 Optical Imaging (BV;WINGS-OPT) Fiber Spectroscopy (WINGS-SPE); 48 clusters NIR Imaging (JK; WINGS-NIR); 28 clusters

WINGSdatabase Astro Pizza - Padova 4 Feb Follow-upimaging * U-band; 18 clusters (almost completed) * H a narrow-band few clusters so far (ongoing) * BV, Very Wide-Field ~50 clusters; (planned) AD HOC Software * GASPHOT automated automated surface surface photometry photometry * MORPHOT automated automated morphological morphological classification classification * SIMSPEC SFHs and SFHs and stellar masses stellar masses

Wings Catalogs Optical photometry (Fasano et al. 2006, Varela et al in press) Near-IR catalogs release (Valentinuzzi et al in press) Spectroscopic catalog release (Cava et al in press) Line measurements and star formation histories (Fritz et al. 2009a in prep., 2009b in prep.) Morphology and sur. phot. catalogs (Fasano et al. 2009, in prep., DOnofrio et al. in prep.) Lick Indices Release (Hansson et al in prep.) UV catalogs release (Omizzolo et al. 2009, in prep.)

FORMULATING A WORKING HYPOTHESIS What if what really matters is the primordial matter density (primordial environment, if you like) AND the primordial available mass That correlates with the distributions of local projected future density global environment galaxy mass + additional mechanisms on some galaxies required (eg. post- starbursts) – is there ANY evidence that a group-specific mechanism (=strangulation) is needed?? How different from common picture? FROM BLUE TO RED ON A COSMIC SCALE: either it happens in groups, or it is intrinsic – but it cannot happen in all groups, as testified by the large scatter in galaxy properties in groups – so, hard to be explained by strangulation