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.