evidence for outflows in rest-uv spectra of z~1-2 ulirgs
DESCRIPTION
Manda Banerji. FIR2011. The VISTA Hemisphere Survey (VHS). Evidence for Outflows in Rest-UV Spectra of z~1-2 ULIRGs. Manda Banerji (IoA, Cambridge) - PowerPoint PPT PresentationTRANSCRIPT
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The VISTA Hemisphere Survey (VHS)
Manda Banerji (IoA, Cambridge)
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)
FIR2011Manda Banerji
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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
FIR2011Manda Banerji
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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?
FIR2011Manda Banerji
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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
FIR2011Manda Banerji
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Comparison to optical SF galaxies
Weiner et al. (2009)
FIR2011Manda Banerji
Banerji et al. (2011)
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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.
FIR2011Manda Banerji
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Galaxy Properties – IStar Formation Rates and Dynamical
MassesLarge 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.
FIR2011Manda Banerji
Optical
Banerji et al. (2011)
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Galaxy Properties – IIStellar Masses
Median Stellar Mass
Reference
z~1.3 SMGs (SED fitting)
(3±0.2)×1010 M Banerji et al. (2011)
z~1.3 SFRGs (SED fitting)
(6±0.8)×1010 M Banerji et al. (2011)
z~1.3 SMGs (constant M/L)
(4±0.2)×1010 M Banerji et al. (2011)
z~1.3 SFRGs (constant M/L)
(2±0.2)×1010 M Banerji et al. (2011)
z~2 SMGs (Photo-z) (9±0.9)×1010 M Wardlow et al. (2011)
z~2 SMGs (Spec-z) (7±1.0)×1010 M Hainline et al. (2011)
FIR2011Manda Banerji
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Galaxy Properties – IIStellar Masses
Median Stellar Mass
Reference
z~1.3 SMGs (SED fitting)
(3±0.2)×1010 M Banerji et al. (2011)
z~1.3 SFRGs (SED fitting)
(6±0.8)×1010 M Banerji et al. (2011)
z~1.3 SMGs (constant M/L)
(4±0.2)×1010 M Banerji et al. (2011)
z~1.3 SFRGs (constant M/L)
(2±0.2)×1010 M Banerji et al. (2011)
z~2 SMGs (Photo-z) (9±0.9)×1010 M Wardlow et al. (2011)
z~2 SMGs (Spec-z) (7±1.0)×1010 M Hainline et al. (2011)
Large scatter in stellar mass estimates due to degeneracies between stellar mass, SFH and dust extinction in SED fits.
FIR2011Manda Banerji
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Galaxy Properties – IIStellar Masses
Median Stellar Mass
Reference
z~1.3 SMGs (SED fitting)
(3±0.2)×1010 M Banerji et al. (2011)
z~1.3 SFRGs (SED fitting)
(6±0.8)×1010 M Banerji et al. (2011)
z~1.3 SMGs (constant M/L)
(4±0.2)×1010 M Banerji et al. (2011)
z~1.3 SFRGs (constant M/L)
(2±0.2)×1010 M Banerji et al. (2011)
z~2 SMGs (Photo-z) (9±0.9)×1010 M Wardlow et al. (2011)
z~2 SMGs (Spec-z) (7±1.0)×1010 M Hainline et al. (2011)
Evidence that z~1.3 SMGs have smaller stellar masses than those at z~2 ??
FIR2011Manda Banerji
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Individual Spectra
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
FIR2011Manda Banerji
Banerji et al. (2011)
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Stacked SpectrumFIR2011Manda Banerji
Various FeII (2344,2374,2383,2600) and MgII (2796,2803) show up prominently in stacked spectra. Can measure their velocity relative to [OII]
Banerji et al. (2011)
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Outflows
OII redshift
MgII terminal
MgII centroid
FIR2011Manda Banerji
Doublet is clearly blueshifted
Banerji et al. (2011)
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Outflows
OII redshift
MgII terminal
MgII centroid
FIR2011Manda Banerji
Count pixels between -500 and -100 km/s to determine centroid
Banerji et al. (2011)
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Outflows
OII redshift
MgII terminal
MgII centroid
FIR2011Manda Banerji
Centroid velocity -240±50 km/s
Banerji et al. (2011)
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Outflows
OII redshift
MgII terminal
MgII centroid
FIR2011Manda Banerji
Count pixels between 90-100% of cont to determine terminal v
Banerji et al. (2011)
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Outflows
OII redshift
MgII terminal
MgII centroid
FIR2011Manda Banerji
Terminal v: -540±100 km/s
Banerji et al. (2011)
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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)
FIR2011Manda Banerji
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Outflow Velocity and SFRFIR2011Manda Banerji
Local LIRGs/ULIRGs
AGN ULIRGs with very large velocities
Banerji et al. (2011)
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Outflow Velocity and SFRFIR2011Manda Banerji
No evidence for difference in outflow v between AGN and SB and AGN SMGs/SFRGs consistent with local SBs rather than local AGN ULIRGs
Banerji et al. (2011)
Local relation after correcting for projection effects
Momentum-driven wind model from Martin et al. (2006)
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Outflow Velocity and SFRFIR2011Manda Banerji
Slight increase in v with SFR but both high and low SFR samples are consistent with local relation and momentum-driven wind model
Banerji et al. (2011)
Local relation V α SFR0.3 after correcting for projection effects
Momentum-driven wind model from Martin et al. (2006)
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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
FIR2011Manda Banerji
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Prospects for Herschel• AGN and SB dominated galaxies driving similar
velocity winds.
FIR2011Manda Banerji
• Herschel observations will help confirm the above
• Suggests that radiative pressure from AGN doesn’t accelerate winds and/or starburst is as bolometrically important as AGN
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Prospects for ALMA• Low ionisation gas outflows of around -200-300
km/s seen in SMGs and SFRGs at z~1.3
FIR2011Manda Banerji
• 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?