Alfredo Carpineti, S. Kaviraj, D. L. Clements, D. Darg, A. K. Hyde, C. Lintott

The Infrared Properties Of

Local Mergers

The Merger catalogue

• Blind Infrared Study

• 3003 mergers from SDSS with z < 0.1 (Darg et al. 2010)

• Cross-matched with the IIFSCz(Wang & Rowan-Robinson 2009)

• 18% IRAS detected, 98% of which LTGs

• Poor IRAS resolution is an advantage

The UnDetected Mergers

• SFR(2*Ha) is a good approximation to SFRFIR

• From that we can extract an expected FIR flux

• Our IR detected mergers are the bright end of the bell curve

The Infrared properties

• Median Luminosity for IRAS-detected mergers is 1011 L⦿

• Median SFR (Kennicut et al.1998) 15 M⦿yr-1

SFR and Environments

• SFR independent of environment

• Environment density calculated using Schawinski et al. 2007

SFR and Mass/Mass Ratio

• SFR doesn’t depend on mass ratio but only on the total stellar mass of the system

Emission Line Activity

• AGN Fraction rises with L(IR)

• All the ULIRGs have AGN and are in a late merger state (c.f. Mirabel & Sanders 1996)

LIRG to ULIRG timescale

• How long does it take for a LIRG evolve?

• Morphological difference between LIRGs and ULIRGs

• All ULIRGs have core separation <5Kpc (4/10 already coalesced)

• 98% LIRGs have a core separation > 5Kpc

• Merger bias? ULIRGs from IIFSCz: 73% are post-mergers

LIRG to ULIRG timescale

• Newtonian approach -> how fast can a LIRG turn into a ULIRG?

• Median timescale 46 ± 16 Myr

Conclusions• 606 matches with the IIFSCz (18% GZ SDSS mergers)

• On average they have LIRG luminosity

• Prefer low density environment, SFR constant respect to environment

• SFR depends on the total mass, independent of mass ratio

• AGN fraction increases with L(FIR), agreement with LIRGs/ULIRGs studies

• LIRG to ULIRG timescale has a lower limit of 46 Myr

Conclusions

The average infrared bright merger is a minor spiral-spiral LIRG, which lives in a low density environment, has a moderate star-formation rate and possibly some form of AGN activity

Carpineti et al. (in preparation)