M. Arnaboldi  ICPNe as probes of diffuse light in clusters July 2 nd, 2005 Magda Arnaboldi, PNe as Astronomical Tools July 2 nd, 2005 Intracluster Planetary Nebulae as Dynamical Probes of the Diffuse Light in Galaxy Clusters Magda Arnaboldi INAF, Observatory of Turin Observations of Diffuse Light Intracluster Light in Cosmological Simulations ICPNe in the Virgo Cluster: projected phase-space distribution Future prospects

M. Arnaboldi  ICPNe as probes of diffuse light in clusters July 2 nd, 2005  Zwicky claimed the discovery of diffuse light in the regions between galaxies belonging to the Coma cluster.  Follow-up photographic surveys for diffuse light in Coma and rich clusters.  CCD photometry of diffuse light. First accurate measurements in Coma (Berstein et al. 1995). Problems  typical surface brightness of the ICL is less than 1% of sky brightness;  it is difficult to disentangle between diffuse light associated with the halo of the cD galaxy at the cluster centre and the diffuse light component Observations of ICL in clusters Since 1995, large CCD and mosaic cameras have allowed measurements of ICL in Abell clusters.

M. Arnaboldi  ICPNe as probes of diffuse light in clusters July 2 nd, 2005 Diffuse light measured in z ∼ 0.25 clusters from stacking of SDSS imaging data. SB measurements of the ICL ranges from 27.5 mag ” at 100 kpc to 32 mag ” at 700 kpc in the observed R band ( Zibetti et al. 2005). Measurements of  * in nearby clusters Presence of diffuse light is traced by existence of tails, arcs and/or plumes with typical  B = 27.8 mag ”, very narrow (~ 2 kpc ) and extended (~ 100 kpc) in Coma and Centaurus. (Gregg & West 1998, Threntam & Mobasher 1998, Calcáneo-Roldán et al. 2000) Diffuse light measured by deep CCD photometry out to large radii in clusters. (Abel 1651 : Gonzalez et al. 2000; Abell 1413 & MKW7: Feldmeier et al. 2002, 2004a; HGC 90: White et al. 2003; Gonzalez et al. 2004).

M. Arnaboldi  ICPNe as probes of diffuse light in clusters July 2 nd, 2005 An alternative method for probing intracluster light is through the direct detection and measurements of the stars themselves Direct detections of IC stars Intergalactic SupernovaeNovae Intergalactic Supernovae ( Gal-Yam et al ) & Novae ( Neil et al ). Intergalactic Globular Clusters Intergalactic Globular Clusters ( West et al. 1995, Jordàn et al ) UltraCompact Dwarfs UltraCompact Dwarfs ( Drinkwater et al ) Intracluster red giant stars (IRGB) Intracluster red giant stars (IRGB) ( Ferguson, Tanvir & von Hippel, 1998; Durrell et al ). Excess of red number counts in Virgo IC fields with respect to the HDF. Compact isolated HII region Compact isolated HII region ( Gerhard, Arnaboldi, Freeman, Okamura 2002 ). It will dissolve by internal process in 10 8 yr. Stars and metals will then be added to the diffuse stellar population nearby. IC HI cloud IC HI cloud ( Oosterloo & Van Gorkom 2005) IC stars and gas in Virgo cluster

M. Arnaboldi  ICPNe as probes of diffuse light in clusters July 2 nd, 2005 ICL smoothly distributed and dynamically old Merritt (1984): The ICL is removed from galaxies early during the cluster collapse and its distribution is predicted to follow closely that of galaxies. ICL smoothly distributed and dynamically old We expect different distribution functions f(x,v) for the ICL depending on the formation mechanism. ICL still distributed in tails or plumes, dynamically young. Moore et al. (1996): the ICL is produced during galaxy harassment and tidal stirring during late infall. ICL still distributed in tails or plumes, dynamically young. The ICL in cluster is relevant for the baryonic fraction condensed in stars, star formation efficiency, and the metal enrichment of ICM via IC stars, especially in the cluster centre. It contains a fossil record of galaxy evolution and interactions in the cluster. Importance of ICL in galaxy clusters

M. Arnaboldi  ICPNe as probes of diffuse light in clusters July 2 nd, 2005 Cosmological Simulations of Cluster Formation High-resolution resimulation of a part of a Universe that collapes into a galaxy cluster. Dark matter subhalos grow, fall into the cluster, may survive or merge into larger halos.  same processes may act on stars in galaxies, producing also ICL from Springel et al. (2001)

M. Arnaboldi  ICPNe as probes of diffuse light in clusters July 2 nd, 2005 Transvr. Velocities Radial Velocities R,V z x,V z y,V z Velocity distributions and projected phase space diagrams for the IC stars N. Napolitano et al. 2003, ApJ, 594, 172 The two-dimensional phase space diagrams in one cluster show filaments, clusters of particles, and empty regions, all of which indicate a young dynamical age!

M. Arnaboldi  ICPNe as probes of diffuse light in clusters July 2 nd, 2005 Cosmological Hydrodynamic Simulations with Star Formation and Feedback Studies of ICL in cosmological simulations require a model of star formation from cold gas, including cooling and feedback effects. Recent studies are by Murante+2004, Willman+2004, Sommer- Larsen Here we use Gadget-2 with the two-phase model of Springel & Hernquist (2003). Current hydrodynamic simulations have significantly lower particle number than dark matter only simulations. Thus they cannot resolve small galaxies in clusters, probably causing overestimate of predicted ICL fraction. Recent high-resolution simulations obtain correct half- mass radii for galaxies above few M . The large galaxies contribute a substantial part of the ICL; this part can be studied. Galaxies must be identified by a substructure-finding algorithm; here we use SKID (Stadel 2001).

M. Arnaboldi  ICPNe as probes of diffuse light in clusters July 2 nd, 2005 ICL in a Cosmological Tree+SPH Simulation Gadget-2 ( V. Springel ) Star Formation Cooling (Z=0) 2x480 3 particles Mass Resolution: DM: h -1 M  Gas: h -1 M  Softening: 7.5 h -1 Box Size: 192 h -1 Mpc  CDM Concordance model (  8 =0.8) G. Murante et al. 2004, ApJ, 607, L83 We identified 117 clusters with M>10 14 h -1 M  Stars in clusters were divided in two classes: bound & unbound. we evaluated radial density profiles of the two components

M. Arnaboldi  ICPNe as probes of diffuse light in clusters July 2 nd, 2005 “stacked” 2D star profile used. Fit range: from center to central surface density Sersic fit is critically sensitive to the range at large radii!  =3.66 ( total average ), 4.37 ( low-luminosity objects ), 1.24 ( high luminosity objects ) Clear evidence for ICL at large radii! Sersic fits ICL more centrally concentrated than galaxy light (see also Zibetti et al. 2005) Galaxies ICL Sersic fit

M. Arnaboldi  ICPNe as probes of diffuse light in clusters July 2 nd, 2005 ICL fractions, star ages More massive clusters show greater ICL fractions Stars in field are older than stars in galaxies (“slow” tidal effects?). Murante et al. 2004; see also Sommer-Larsen et al. 2005

M. Arnaboldi  ICPNe as probes of diffuse light in clusters July 2 nd, 2005 High resolution cosmological simulations Gadget-2 ( V. Springel ) Star Formation Cooling (Z=0) Feedback particles in Cluster Mass Resolution: DM: h -1 M  Gas: h -1 M  Softening: 2.1 h -1 Mass h -1 M  Virial R: 1.1 h -1 Mpc  CDM Concordance model (  8 =0.8, h=0.7) Borgani et al. (2005)

M. Arnaboldi  ICPNe as probes of diffuse light in clusters July 2 nd, 2005 Distribution of Dark Matter and Stars z=3 z=1 z=0 Murante et al. 2005, in prep.

M. Arnaboldi  ICPNe as probes of diffuse light in clusters July 2 nd, 2005 Galaxies and Intracluster Stars z=3 z=1 z=0

M. Arnaboldi  ICPNe as probes of diffuse light in clusters July 2 nd, 2005 PNe trace light because the luminosity-specific stellar death rate should be independent of the precise state of the underlying stellar population (Renzini & Buzzoni 1986). The [OIII] line emission at 5007Å is the strongest emission from a PN; it allows the identification & the measurement of its radial velocity We obtain PN number density distribution and 2D radial velocity fields in regions where the stellar surface brightness is too faint with respect to the night sky! ICPNe in the Vigo cluster: projected phase-space distribution ON-H  ON-[OIII] OFF-(V+R)

M. Arnaboldi  ICPNe as probes of diffuse light in clusters July 2 nd, 2005 ICPNe as light tracers ICPNe as light tracers : 1.Narrow band imaging surveys with large field mosaic cameras 2.2m tel. + 2.Development+tests of selection criteria based on photometric catalogs from Sextractor (Arnaboldi et al. 2003, ESO Messenger 112, 37) for the identification of the ICPNe associated with the ICL (Arnaboldi et al. 1996, 2002, 2003; Okamura et al. 2002; Feldmeier et al. 1998, 2002, 2003, 2004; Aguerri et al. 2005, AJ, 129, 2585 ). Planetary Nebulae as tracers of cluster evolution ICPNe as kinematical tracers ICPNe as kinematical tracers : 1.Follow up studies aiming at measuring spectra from multi-slit spectrograph ( ESO VLT ; Gerhard et al. 2002, ApJ, 580, L121, Arnaboldi et al. 2003, AJ, 125, 514 ) 2. First spectra from multi-fiber spectrograph for a statistical significant sample of ICPN ESO VLT; Arnaboldi et al. 2004, ApJ, 614, L33 ; ESO PR 24/04)

M. Arnaboldi  ICPNe as probes of diffuse light in clusters July 2 nd, 2005 Mosaic image in [OIII] obtained at the 2.2m tel. Current surveys Layout of the fields already acquired within this project in the Virgo cluster (Map of Virgo from Binggelli et al. 1987). Mosaic image in [OIII] obtained with the 8.2m tel.

M. Arnaboldi  ICPNe as probes of diffuse light in clusters July 2 nd, 2005 Results from narrow band surveys The ICPNe number density distribution in the Virgo cluster is highly inhomogeneous: inhomogeneous distribution in single fields, field-to-field number density fluctuations. The distribution of ICPNe in the Subaru field is highly inhomogeneous No ICPN in LPC. Agreement with Kud+2000 HST RGBs. From Aguerri, Gerhard, Arnaboldi & al. 2005, AJ, 129, 2585

M. Arnaboldi  ICPNe as probes of diffuse light in clusters July 2 nd, 2005 Results from narrow band surveys (cont.) Significant field-to-field variation of the ICL in the Virgo cluster No clear number density trend with distance from cluster center in M87 Mean surface luminosity density of ICL in Virgo core : L  ’ (note the large rms = L  ’ due to field-to-field variations!) Mean surface brightness of ICL in Virgo core :  B =29 mag ” Mean fraction of light in ICL: <10 % (Aguerri et al. 2005; see also Feldmeier et al. 2004) Fraction of stars in the ICL increases with the density of the environment: <2% in loose groups (Castro-Rodriguez+2003, Durrel et al. 2004), <10% in Virgo-like (Arnaboldi et al. 2003, Feldmeier et al. 2004, Aguerri et al. 2005),  20% in rich clusters including cD halos (Gonzalez et al. 2000, Feldmeier et al. 2002, Zibetti et al. 2005).

M. Arnaboldi  ICPNe as probes of diffuse light in clusters July 2 nd, 2005 Results from spectroscopic follow-up…. April 2002 VLT & TNG (in the Subaru field only) March 2003 VLT for FCJ, Core and Subaru fields Flames FOV. FORS2 & Flames of ICPNe spectra show the [OIII] doublet! ICPN single spectra M.Arnaboldi et al. 2004, ApJ, 614, L33 Ly 

M. Arnaboldi  ICPNe as probes of diffuse light in clusters July 2 nd, 2005 ICPNe: they are brighter than the PNLF cut off for M87 M87 PN in the M87 halo v mean = 1280 km/s  =240 km/s M86 M84 NGC 4388

M. Arnaboldi  ICPNe as probes of diffuse light in clusters July 2 nd, Observed ICPN radial velocities in the Subaru field Flames FOV I34, I35, I36, I38 are over-luminous [OIII] emitters & are bound to M84 – Pop. Effects.

M. Arnaboldi  ICPNe as probes of diffuse light in clusters July 2 nd, 2005 Implications on adopted criteria We understand the selection biases that may lead to wrong identification, i.e. continuum objects erroneously classified as emission line, in on-off imaging surveys on mosaic frames. The fraction of spectroscopically confirmed targets is now f >80 % (down to the limiting magnitudes), while in Freeman et al. (2000) was 50%! Summary spectroscopic results! Giant galaxies in clusters are very extended - PNe still associated with M87 out to ~70 kpc & very extended halo also around M84 The velocity histograms show strong field-to field variations. Dynamical times at the location of these fields are from 2× 10 8 yr (FCJ) to 8×10 8 yr (SUB). Phase mixing to erase field-to-field variations would take few Gyr.

M. Arnaboldi  ICPNe as probes of diffuse light in clusters July 2 nd, 2005 Conclusions 1.Observations indicate that diffuse light is important in understanding cluster evolution, star formation history and the ICM enrichment. 2.Measuring the projected phase space constraints how and when this light originated and ICPNe are the only abundant stellar component of the ICL whose kinematics can be measured. 3.We can then explore the effect of low/dense environment on galaxy evolution with MSIS technique! (see O. Gerhard’s talk, this conference. )

M. Arnaboldi  ICPNe as probes of diffuse light in clusters July 2 nd, 2005