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The distribu,on of massive compact relics in the nearby universe Aldée Charbonnier1, Marc Huertas-‐Company2, Huanyuan Shan3, Kevin Bundy4, Thiago S. Goncalves1, CS82 collabora,on
1Observatório do Valongo -‐ UFRJ, Rio de Janeiro, Brazil 2University Paris 7, Observatoire de Paris-‐Meudon, Paris, France
3LASTRO, EFPL, Switzerland 4Kavli, IPMU – University of Tokyo, Japan
IAU Symposium 311 – Galaxy Masses as Constraints of Forma 2. The cross correla,on is shown as a func,on of the correla,on length θ. Conclusion: we do not see currently any cross-‐correla,on between peaks of the mass maps and massive compact quiescent candidates. We note that we have observed a contamina,on by stars in our sample.
The Canada-‐France-‐Hawaii Telescope Stripe-‐82 (CS82) project consists in an i-‐band survey, covering 173 deg2 of the SDSS equatorial Stripe 82 (Erben et al., in prep). Data have been obtained in excellent seeing condi,ons (between 0.4 and 0.8 arcsec with a median of 0.59 arcsec), down to a 5σ limi,ng magnitude of iAB≈24.0. CS82 survey was designed primarily for lensing analysis, probing mass distribu,on with redshij < 0.7. The SDSS Stripe-‐82 equatorial region is currently one of the richest region of the sky in terms of mul,-‐wavelength coverage associated to a large area. An interna,onal effort is going on to join all efforts. Primarily, SDSS has scanned repeatedly this area, providing photometric data in ugriz down to r23.5 for galaxies (Annis et al. 2011). Furthermore, data are also available in op,cal (DES, HSC, GALEX, Pan-‐STARRS), near-‐infrared (IR; UKIDSS, VHS, NEWFIRM, 2MASS), mid-‐IR (Shela, SpIES, WISE, VICS82), far-‐IR (HELMS, HerS), radio (VLA, ACT, Planck) and X-‐ray (Chandra, XMM, Swij, NuSTAR) wavelengths. Various spectroscopic surveys have been conducted so far (SDSS, HETDEX, Wigglez, VVDS, DEEP2, PRIMUS…). This setup allows unique sta,s,cal studies of galaxy popula,ons.
0.2 < z < 0.3 0.3 < z < 0.4
0.4 < z < 0.5 0.5 < z < 0.6
‘quiescent’
stars
With the excep,onal quality of CS82 images, it is possible to calculate morphological proper,es of a large sample of objects, reaching current limit of large scale surveys. We have used two sojwares developed to be run together: SExtractor (Ber,n & Arnouts, 1996, v2.18.8) for the detec,on and the morphometric es,ma,on, and PSFEx (Ber,n 2011, v3.15.0) for the Point Spread Func,on (PSF) reconstruc,on. Different profiles have been fi\ed to the en,re survey: de Vaucouleurs, general Sersic, and exponen,al (Moraes et al. in prep). Stellar masses and redshijs were derived using SYNMAG photometry tool (Bundy et al. 2012). The catalogue is based on Annis et al. (2011) work on the coadds of the SDSS Stripe-‐82,and taking advantage of IR data provided by UKIDSS. Priority is given to spectroscopic redshijs when available. Some regions were masked to avoid bright stars and cosmic rays and also regions were the PSF is poorly constrained. Only galaxies with stellar mass > 5x1010 M⨀, magnitude i < 21, and redshijs 0.2 < z < 0.6 are considered.
galaxies
compact
The star/galaxy classifica,on is performed using the SPREAD_MODEL parameter, produced by SExtractor. It takes into account the shape of the PSF. The star branch appears clearly in the SPREAD_MODEL vs. Kron magnitude plan.
Matched objects with the SDSS star catalogue of Ivezic et al. (2007), despite a contamina,on by galaxies, are indeed located on the iden,fied stellar locus.
It is now well accepted the presence of a popula,on of massive/passive very compact galaxies at high redshijs. Whether this primordial popula,on evolves to match the proper,es of today’s massive ellip,cals (e.g van der Wel et al. 2014) or simply remains as a marginal popula,on of relics in the local universe is s,ll an open debate in the literature (Carollo et al. 2013, Poggian, et al. 2013a). In par,cular, li\le is known on how the abundance of these objects in the local universe correlates with environment. Given that they are massive and formed at very early epochs, one might naturally think that they will end up in massive dark ma\er structures today (e.g Poggian, et al. 2013b) We use the SDSS/Stripe-‐82 Megacam imaging (seeing ~0.6”) to perform a systema,c search of compact galaxies in the redshij range 0.2 < z < 0.6 and compute the correla,on between their spa,al distribu,on and the dark ma\er density peaks.
We take advantage of the bimodality of the color histogram, when choosing the adequate bands around the 4000 Å break, according to the bin of redshij considered. An example is shown above for 0.3 < z < 0.4 (following Strateva et al. 2001).
The next steps of our study mainly take advantage of the large amount of data available on the Stripe-‐82 (e.g. Stripe-‐82 Princeston Workshop, March 2014), they include:
• Reconsider the star/galaxy separa