# CosmoBias: International Meeting on Physical Bias in Cosmology

When: May 22-25, 2012

Where: Laboratoire d'Astrophysique de Marseille (LAM), Marseille

...you don't know Marseille?! Visit us!

*How to arrive at LAM? See "Practical Informations" at the bottom of this page!*

### Rationale

The galaxies and intergalactic gas we see in all the wavelengths from radio to X-ray constitute a tiny fraction of the total matter of the Universe. Most of the gravitating matter is indeed dark, i.e. it does not interact with the radiation and the baryonic components while being detectable only through its gravitational effects. The bias between the “luminous” and dark matter components represents one of the more striking problems of modern cosmology.

Objects like galaxy clusters, galaxies, Lyman-alpha emitters or the intergalactic gas trace the underlying (dark) matter field in a different way; the study of the spatial statistics of the different tracers as function of the cosmic epoch (redshift), scale, and intrinsic properties of the tracers themselves (mass, luminosity, color, etc.) provides a mean to describe in an effective way the complex, non-linear history of structures’ formation from galactic to cosmological scale. For a fixed distribution of dark matter, which mainly depends on gravitational interactions, proper modeling the bias function accounting for stochasticity, time-dependence, etc. usually allows for a coarse-grain picture of the intricate, astrophysical processes occurring on small scale.

The structure and dynamics of cosmic structures can also keep track of possible and very likely small non-standard features of the primordial and late-time Universe: the presence of primordial non-Gaussianities in the initial matter fluctuations; the mixture of different kinds of dark matter such as cold, warm, and hot components (sterile and massive neutrinos, etc.); the dynamics of dark energy; the coupling between dark matter and dark energy; the departure from general relativity on large scales; etc. The (direct or indirect) dependence of the observables on the cosmic bias is a mandatory step in the light of the forthcoming “precision cosmology”, which is called to unveil the aforementioned fundamental issues exploiting extraordinary ground-based and spatial observational programs such as VIPERS, BOSS, DES, Big-BOSS or EUCLID.

Several techniques are currently used and continuously developed to investigate cosmic bias: spatial clustering, redshift space distortions, weak gravitational lensing, Lyman-alpha forest, etc., as well as combinations thereof through cross-correlations.

In the same spirit of the very successful, previous international meetings hosted at Marseille/LAM since 2008 (CosmoTools in 2008, CosmoClusters in 2009, CosmoZsurvey in 2010, CosmoFirstObjects in 2011), Cosmo-Bias is intended as an informal 3/4-days conference with only invited speakers to discuss about the most recent modeling and observations of the mass-luminosity relation on cosmological scales. As in the previous Cosmo- meeting editions, the greatest interaction between participants will be assured by alternating talks and several free and leaded discussions, including keynotes at the end of each day. With the purpose of fostering new ideas and collaborations, the major actors at the forefront of these fields are invited, and the attendance of undergraduate (master) and PhD students is highly encouraged. Aiming to offer an informal and productive ambience, the attendance is limited to 50 people.

### Topics

*Theoretical modeling of cosmic bias*– global, local, deterministic, stochastic, time-dependent, luminosity-dependent, color-dependent, ...*Mass bias: from dark matter to halos*– use of galaxy clusters, degeneracy bias-primordial non-gaussianities, 3-point correlation functions, ...*Luminosity bias (I): from halos to galaxies*– the halo occupation distribution modeling as function of spectral-type, colors, ...*Luminosity bias (II): the cosmic web of the first stars*– bias of intergalactic gas, Lyman systems, first objects, ...*Feedback of astrophysical processes on LSS*– the link between large-scale structures and small-scale structures accounting for radiative processes, stellar winds, ...*Bias by cross-correlations and higher-order statistics*– the combined use of galaxy clustering, weak gravitational lensing, etc. at 2-3-*n*order

### Program

**Schedule:**start at 2:20pm, end around 6pm.**Tue 22:**start at 9:10am, end around 6 pm.**Wed 23 and Thu 24:**start at 9:10am, end at noon.**Fri 25:***Reviews:*30 min,*Talks*: 25 min (all including questions, 5 min),*Daily keynote sessions*: 40+ min

### Participants

➣ *Invited review talks*:

Rennan Barkana (Tel Aviv University), Carlton Baugh (ICC, Durham), Benedetta Ciardi (MPA, Garching), Enrique Gaztañaga (IEEC Barcelona), Ofer Lahav (UCL, London), Cristiano Porciani (AIfA, Bonn)

➣ *Contributed talks*:

Ummi Abbas (INAF - OA Torino), Julien Bel (CPT, Marseille), Christopher Bonnett (CSIC/IEEC, Barcelona), Marcello Cacciato (Racah Institute of Physics, Jerusalem), Gabriel Caminha (LAM, Marseille & CBPF Brazil), Andrea Cattaneo (LAM, Marseille), Johan Comparat (LAM, Marseille), Jean Coupon (Institute of Astronomy and Astrophysics, Taipei), Cinzia Di Porto (INAF - OA Bologna), Anna Elia (AIfA, Bonn), Anastasia Fialkov (Tel Aviv University), Violeta Gonzalez-Perez (ICC, Durham), Ben Granett (INAF - OA Brera), Nico Hamaus (University of Zürich), Eric Jullo (LAM), Kai Hoffmann (IEEC, Barcelona), Lars Koens (IfA Edinburgh), Marc Manera (ICG, Portsmouth), Federico Marulli (Università di Bologna), Takamitsu Miyaji (IA-UNAM Ensenada & UC San Diego), Jennifer Pollack (AIfA, Bonn), Arnau Pujol (IEEC, Barcelona), Nina Roth (AIfA, Bonn), Holger Schlagenhaufer (MPE, Garching), Huan Yuan Shan (Tsinghua Center for Astrophysics, Beijing), Fergus Simpson (IfA, Edinburgh), Marcel van Daalen (Leiden Observatory), Idit Zehavi (Case Western Reserve University, Cleveland)

➣ *Other participants*:

Stéphanie Escoffier (CPPM, Marseille), Sylvain De La Torre (IfA, Edinburgh), Fabien Lacasa (IAS, Orsay), Vincent Le Brun (LAM, Marseille), Alain Mazure (LAM, Marseille), Francesco Montanari (Université de Genève), Aurelie Penin (LAM, Marseille), T. Schucker (CPT, Marseille), Laurence Tresse (LAM, Marseille)...

➣ *LOC/SOC*:

O. Cucciati (INAF - OA Trieste), J.-P. Kneib (LAM, Marseille), C. Marinoni (CPT, Marseille), C. Schimd (LAM, Marseille)

➮➮➮➮ *If interested to come (and give a talk) please contact one of us:* carlo.schimd@oamp.fr , jean-paul.kneib@oamp.fr , cucciati@oats.inaf.it, chris.marinoni@gmail.com

### Practical informations

Lunch:

**offered**by LAM Cosmology Group to confirmed participants.Marseille/Nice/Lyon airport, then shuttle/train (TGV) to Marseille. In particular:**How to arrive at LAM:**Nice airport ➠ Marseille downtown ("St. Charles" railway station): train or shuttle

Marseille airport ➠ Marseille downtown ("St. Charles" railway station): shuttle, more general

Marseille downtown ➠ LAM by public transportations (~25 min): metro line n.1 until terminus "La Rose - Technopole Château-Gombert", then bus line n.1 (on the right at the metro’s exit) till "I.M.T." stop, OAMP-LAM is the red-blue building; see the map.

Marseille airport ➠ LAM by taxi: from 30 min to hours... (50-60 euro).

Reservation Here -- suggestions: Vieux Port area, Prefecture area**Hotels:**