The interaction-driven modelfor the starburst galaxies and AGNs

Alessandra LamastraCollaborators:

N. Menci, F. Fiore, P. Santini, A. Bongiorno

Outline

• The interaction-driven model for the starburst galaxies and AGNs

• The contribution of the SB galaxies to the cosmic SFRD

• SFR in AGN host

The SFR-M* relation

Z≈0

Star forming galaxies follow a tight correlation (σ≈0.3 dex) between their stellar mass and the SFR from z=0 to z=6 (Brinchmann et al. 2004, Noeske et al. 2007, Elbaz et al. 2007, Daddi et al. 2007, Santini et al. 2009, Salim et al. 2007, Strak et al. 2009, Gonzalez et al. 2011)

Starburst galaxies

“Main sequence” galaxies

Elbaz et al. (2011)

Disk-like systems Extended SF Large gas depletion time scale (2 Gyr)

Interacting systems SF in the nuclear region low gas depletion time scale (10-few Myr)

Rodighiero et al. (2011)Elbaz et al. (2011)

The contribution of starburst galaxies to the SFRD at z≈2

Rodighiero et al. (2011)

Herschel-PACS COSMOS

Herschel-PACS GOODS

BzK COSMOS

BzK GOODS

Starburst galaxies: SSFR> 4×SSFRMS

SB account for ≈10% of the cosmic SFRD at z≈2

The SFR-M* relation of AGN hosts

Santini et al. (2012) Rovilos et al. (2012)Mullaney et al. (2012)

AGN hosts follow the distribution of SF inactive galaxies

Angela’s talk

The semi-analytic model

DM merging trees

+gas cooling, star formationSN feedback,…

Baryonic processes

• DM merging trees: Monte Carlo realizations• Dynamical processes involving galaxies within DM haloes• Cooling, Disc properies, Star formation and SNae feedback• Starbursts triggered by merging and fly-by events• Growth of SMBH from BH merging + accretion of galactic gas destabilized by galaxy encounters (merging and fly-by events) • Feedback from the AGN associated to the active, accretion phase

+

SMBH growth

(Menci et al. 04,05,06,08)

Star formation and BH accretion

Kennicutt 1998

Quiescient star formation

Starburst driven by (major+minor) merging and fly-by events

Frequent galaxy interactionsRapid cooling (high gas density)Starbursts with large fraction of gas converted into stars

Drop of interaction rateDecline of cooling rateQuiescent and declining star formation

z>2

z<2

SMBH accretion rate

The predicted SFR-M* relation

SAM

Rodighiero et al. (2011)

Santini et al. (2009)

(see also Daddi et al. 2004, Davè 2008, Fontanot et al. 2009, Santini et al. 2009)

Offset between the observed and predicted SFR-M* relation

GOODS-MUSIC catalog

GOODS /COSMOS Herschel-PACS/BzK galaxies

SSFR-cut used by Rodighiero et al. (2011) to identify starburst galaxies: SSFR > 4 x SSFRMS

The SSFR distribution

SFRq>SFRb

SFRb>SFRq

SSFR>tH-1

SSFR>SSFRMS/4

Rodighiero et al. (2011)

The contribution of MS and SB galaxies to the cosmic SFRD

Quiescent SF

Burst-like SF

The contribution of the burst-dominated SF systems increases with redshift, rising from 1%-5% at z≈0 to 25%-27% at z=5-6

The interaction-driven scenario for the starburst galaxies is consistent with the observational constraints indicating that starburst galaxies contribute for ≈ 10% of the cosmic SFRD at 1.5<z<2.5

1.5<z<2.5

AGNs in starburst galaxies

The fraction of AGN hosted in starburst galaxies is an increasing function of the AGN luminosity

Summary

• The interaction-driven scenario for the starburst galaxies is consistent with the observational constraints indicating that starburst galaxies contribute for ≈ 10% of the cosmic SFRD at 1.5<z<2.5.

• The interaction-driven model provides strict predictions for the evolution of the starburst contribution to the cosmic SFRD and for the number of AGN hosted in starburst galaxies as a function of the AGN luminosity.