Evidence for Outflows in Rest-UV Spectra of z~1-2 ULIRGs

1. Manda Banerji FIR2011 The VISTA Hemisphere Survey (VHS) Evidence for Outflows in Rest-UV Spectra of z~1-2 ULIRGs Manda Banerji (IoA, Cambridge) Scott Chapman (IoA), Ian Smail (Durham), Susie Alaghband-Zadeh (IoA), Mark Swinbank (Durham), Jim Dunlop (Edinburgh), Rob Ivison (Edinburgh), Andrew Blain (Leicester) Manda Banerji (IoA, Cambridge)

2. Manda Banerji FIR2011 Outline • Use rest-UV spectroscopy to trace “cool” ISM in z~1-2 sub-mm galaxies (SMGs) and sub-mm faint radio galaxies (SFRGs) via various absorption lines • Already successfully done for low-z ULIRGs (Martin et al. 2005, 2006) as well as optically selected SF galaxies at z~1-2 (Weiner et al. 2009) • Look for dependence of outflow velocity on different galaxy properties e.g. SFR, stellar mass

3. Manda Banerji FIR2011 Key Questions • How do SMG/SFRGs at z~1-2 compare to lower redshift LIRGs and ULIRGs? • How do they compare to optically selected star-forming galaxies at similar redshifts?

4. Manda Banerji FIR2011 Sample • 19 SMGs (>5mJy at 850 micron) and 21 SFRGs (<5mJy at 850 micron) with KeckII-DEIMOS spectra. All have robust radio IDs. • [OII] + various combinations of [NeV], [NeIII], Hδ, Ca K&H for redshifts • Predominantly MgII and FeII trace cool ISM • Redshift range – 0.7 – 1.7 – median of 1.3 • Average bolometric luminosity of ~1×1012 L-> average SFR of ~100-200 M/yr

5. Manda Banerji FIR2011 Comparison to optical SF galaxies Weiner et al. (2009) Banerji et al. (2011)

6. Manda Banerji FIR2011 Comparison to Previous Studies of SMGs/SFRGs z~1.3 SMGs/SFRGs (Banerji et al. 2011) fill in the redshift desert in previous spectroscopic studies (Chapman et al. 2004,2005) while also probing a lower luminosity population.

7. Manda Banerji FIR2011 Galaxy Properties – IStar Formation Rates and Dynamical Masses Banerji et al. (2011) Large star formation rates of a few hundred solar masses per year (though considerably less than z~2 SMGs/SFRGs) Large nebular linewidths corresponding to large dynamical masses. Optical

8. Manda Banerji FIR2011 Galaxy Properties – IIStellar Masses

9. Manda Banerji FIR2011 Galaxy Properties – IIStellar Masses Large scatter in stellar mass estimates due to degeneracies between stellar mass, SFH and dust extinction in SED fits.

10. Manda Banerji FIR2011 Galaxy Properties – IIStellar Masses Evidence that z~1.3 SMGs have smaller stellar masses than those at z~2 ??

11. Manda Banerji FIR2011 Individual Spectra Banerji et al. (2011) Typical spectrum has a continuum S/N of ~1.7. Although [OII] is detected at high significance in all cases -> redshifts, studies of absorption features impossible

12. Manda Banerji FIR2011 Stacked Spectrum Banerji et al. (2011) Various FeII (2344,2374,2383,2600) and MgII (2796,2803) show up prominently in stacked spectra. Can measure their velocity relative to [OII]

13. Manda Banerji FIR2011 Outflows MgII terminal Doublet is clearly blueshifted MgII centroid OII redshift Banerji et al. (2011)

14. Manda Banerji FIR2011 Outflows MgII terminal Count pixels between -500 and -100 km/s to determine centroid MgII centroid OII redshift Banerji et al. (2011)

15. Manda Banerji FIR2011 Outflows MgII terminal Centroid velocity -240±50 km/s MgII centroid OII redshift Banerji et al. (2011)

16. Manda Banerji FIR2011 Outflows MgII terminal Count pixels between 90-100% of cont to determine terminal v MgII centroid OII redshift Banerji et al. (2011)

17. Manda Banerji FIR2011 Outflows MgII terminal Terminal v: -540±100 km/s MgII centroid OII redshift Banerji et al. (2011)

18. Manda Banerji FIR2011 Outflow Velocity & Stellar Mass No significant trend seen and the outflow velocities are consistent with optically selected star-forming galaxies at similar redshifts from Weiner et al. (2009)

19. Manda Banerji FIR2011 Outflow Velocity and SFR AGN ULIRGs with very large velocities LocalLIRGs/ULIRGs Banerji et al. (2011)

20. Manda Banerji FIR2011 Outflow Velocity and SFR No evidence for difference in outflow v between AGN and SB and AGN SMGs/SFRGs consistent with local SBs rather than local AGN ULIRGs Momentum-driven wind model from Martin et al. (2006) Local relation after correcting for projection effects Banerji et al. (2011)

21. Manda Banerji FIR2011 Outflow Velocity and SFR Slight increase in v with SFR but both high and low SFR samples are consistent with local relation and momentum-driven wind model Momentum-driven wind model from Martin et al. (2006) Local relation V α SFR0.3 after correcting for projection effects Banerji et al. (2011)

22. Manda Banerji FIR2011 Conclusions • Redshift 1.3 SMGs/SFRGs significantly less luminous with lower SFRs than those selected at redshift 2 • Typical outflow velocities of -240 km/s as traced by MgII and FeII ions relative to [OII] • AGN and SB dominated galaxies have similar outflows • Slight increase seen in outflow velocity with SFR • Outflows similar to optically selected star-forming galaxies of similar stellar mass at the same redshifts • Outflows indistinguishable from local LIRGs/ULIRGs

23. Manda Banerji FIR2011 Prospects for Herschel • AGN and SB dominated galaxies driving similar velocity winds. • Suggests that radiative pressure from AGN doesn’t accelerate winds and/or starburst is as bolometrically important as AGN • Herschel observations will help confirm the above

24. Manda Banerji FIR2011 Prospects forALMA • Low ionisation gas outflows of around -200-300 km/s seen in SMGs and SFRGs at z~1.3 • P-Cygni profiles in molecular lines from Arp220 (Sakamoto et al. 2009) – Molecular Outflows. • Predicted in high-z ULIRGs by theoretical simulations (Narayanan et al. 2008) • How do molecular outflows compare to rest-UV ionised gas outflows?