#SMG20 – Durham 2017 Understanding Submillimetre Galaxies: Lessons from Low Redshifts Paul van der Werf Leiden: Marissa Rosenberg Rowin Meijerink Saskia van den Broek Edo Loenen Kirsty Butler Cardiff/ESO :Padelis Papadopoulos ESTEC: Kate Isaak Groningen: Marco Spaans Madrid: Santiago Garcia-Burillo MPIfR: Axel Weiß UCL: Thomas Greve
Know your classics • Casey, Narayanan, & Cooray 2014, Phys Rep , 541, 45 • Carilli & Walter 2013, ARA&A , 51, 105 • Blain, Smail, Ivison, Kneib & Frayer, 2002, Phys Rep , 369, 111 • Scoville, 2012, Canary Winter School, arXiv/1210.6990
Outline • ULIRGs vs. SMGs • Local physical conditions from FIR-submm spectra • Molecular gas mass • Gas outflows
From IRTRONs to ULIRGs • 1984- 1985: IRAS (“ultra - high luminosity”: Houck et al ., 1985)
Local ULIRGs are major mergers (GOALS - Evans et al .) At L IR > 5×10 12 L ʘ , all (U)LIRGs show merging signatures
Babies or monsters? Cool ULIRG Warm ULIRG QSO (Sanders et al ., 1988)
Extreme star formation L IR / L CO SFR/ M H2 SFE (Gao & Solomon, 2001) L 1 ULIRGs : FIR 100 L M M H 2 1 Milky Way : 1 . 5 L M L IR SFR 1 Galactic GMCs : 1 . 8 L M 1 OMC - 1 : 54 L M 1 Orion BN - KL : 400 L M
Strong evolution (Casey et al ., 2014)
ULIRGs vs. SMGs Where does the analogy break down? • At same L IR , T d is lower at high z • CO disks in SMGs are larger than in ULIRGs • Position with respect to Galaxy Main Sequence? (Casey et al ., 2014)
ULIRGs vs. SMGs CO ladders (Greve et al ., 2014) NB: selection, diversity
Outline • ULIRGs vs. SMGs • Local physical conditions from FIR-submm spectra • Molecular gas mass • Gas outflows
Mrk 231 Herschel SPIRE FTS (Van der Werf et al ., 2010)
Mrk 231 CO ladder 2 PDRs + XDR 6.4:1:4.0 n=10 4.2 , F X =28 * n=10 3.5 , G 0 =10 2.0 n=10 5.0 , G 0 =10 3.5 * 28 erg cm -2 s -1 G 0 =10 4.2 (Van der Werf et al ., 2010)
XDRs vs. PDRs Physical differences • X-rays penetrate much larger column densities than UV photons • Gas heating efficiency in XDRs is ≈10— 50%, compared to <1% in PDRs • Dust heating much more efficient in PDRs than in XDRs • CO/[CII] elevated in XDRs compared to PDRs
XDRs vs. PDRs CO ladder Identical total incident energy (Spaans & Meijerink, 2008)
CO cooling fraction as AGN tracer HerCULES sample PAH 6.2 EW traces starburst fraction Mrk231 (Rosenberg et al ., 2015) IRASF05198-2524
CO ladders of local (U)LIRGs Herschel SPIRE/FTS data from HerCULES Identical total incident energy α > 0.66 0.33 < α < 0.66 α < 0.33 α = CO(12−11)+CO(13−12) (Rosenberg et al ., 2015) CO(5−4)+CO(6−5)
Starburst and AGN tracers Principal component analysis of HerCULES lines starbursts CO excitation is the best AGN indicator AGNs ([CII]+[OI])/FIR high in starbursts OH + and H 2 O + do not prefer AGNs (Van den Broek et al ., in prep .)
MPDRs and CRDRs CO ladder • For almost all starbursts, UV heating (PDR) is insufficient. • MPDRs or CRDRs are needed. • Extreme MPDRs are hard to distinguish from XDRs. (Kazandjian et al ., 2015)
Fine-structure line deficits GOALS sample - [CII] 158 μ m, [NII] 122/204 μ m, [OI] 63 μ m, [OIII] 88 μ m (Casey et al ., 2014) (Diaz-Santos et al ., 2017) offset only due to larger size?
[CII] line deficit at for SMGs SPT sample (Spilker et al ., 2016)
Line deficits and physical conditions PDR modeling based on [CII], [OI] and [NII] Transition in properties at ∑ IR = 5×10 10 L ʘ /kpc 2 (Diaz-Santos et al ., 2017)
Outline • ULIRGs vs. SMGs • Local physical conditions from FIR-submm spectra • Molecular gas mass • Gas outflows
H 2 mass from observations of other tracers the invisible molecule H 2 observe excitation of other species = observe H 2 through its collisions Modeling excitation yields conversion factor to H 2 mass
Star formation laws and α CO (Casey et al ., 2014)
α CO from improved data and modeling See talk by Weiß Weiß et al., in prep.
Outline • ULIRGs vs. SMGs • Local physical conditions from FIR-submm spectra • Molecular gas mass • Gas outflows
Self-regulated galaxy buildup Theoretical paradigm star feedback gas outflow gas inflow forming gas observable Infrared, H α , CO, observable HCN, dust, etc CO, H α , X-rays, observable etc. extremely Supernova remnants, AGNs difficult to observe
Mrk 231 outflow in CO (Feruglio et al ., 2010) H 2 O H 2 O absorption emission
Mrk 231 outflow in CO and HCN (Aalto et al ., 2014) The outflowing molecular gas is dense!
Multi-phase outflows CO ladder • Complex structure and velocity field • Out-of-equilibrium chemistry • Relative and total masses? • Observations of multiple phases needed (Wada, Schartmann, & Meijerink, 2016)
H α supernebulae around (U)LIRGs NGC6240 R H α (Armus et al ., 1990)
Ubiquity of molecular outflows Do galaxies where the integrated spectrum does not show wings have no outflows? (García-Burillo et al ., 2014) NGC1068, ALMA
NGC1068 velocity field
NGC1068 outflow
IRAS 17208-0014
IRAS 17208-0014 outflow (García-Burillo et al ., 2015)
Driving (García-Burillo et al ., 2015)
Outflow tracers Can we use OH + and CO(9−8) to trace high -z outflows?
OH + outflow at z = 2.41
OH + in Arp220 Herschel/SPIRE, Rangwala et al., 2012
Hot off the press: OH + in Arp220 with ALMA Band 10 OH+ NH 2 red wing OH + blue wing OH + main absorption
Open questions • CO ladder: what is the role of mechanical and cosmic ray heating and what can we learn from it? • Fine-structure lines: are there deviations from the low-z relation? What happens at low metallicities? • Outflows: how do outflow properties depend on galaxy properties? What is the mass outflow rate? What happens to the outflowing gas? • Extreme star formation: Is Eddington-limited star formation really relevant? • Arp220: What is happening in the obscured nuclei? How can we tell? • SMGs vs . ULIRGs: what do the differences mean? • IMF: universal? Top-heavy? How can we tell?
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