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Star formation relations across the CO ladder and redshift
Thomas R. Greve (University College London)
DeMoGas: Manolis Xilouris (NOA) Ioanna Leonid (NOA) Padelis Papadopoulos (Cardiff) Paul van der Werf (Leiden) Axel Weiss (MPIfR) Zhi-Yu Zhang (PMO/ROE)

http://demogas.astro.noa.gr/

Galaxy Evolution over five decades
Sunday, October 6, 2013

O

Cambridge September 2013


Why are star formation relations interesting?

IC 342 HI (atomic gas)
THINGS

1 kpc

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Why are star formation relations interesting?

IC 342 HI (atomic gas)
THINGS

CO J=1-0 (molecular gas)
12

NRAO 12m

1 kpc

Sunday, October 6, 2013


Why are star formation relations interesting?

IC 342 HI (atomic gas)
THINGS

CO J=1-0 (molecular gas)
12

NRAO 12m

Spitzer 70um

IR emission (star formation) 1 kpc
On kpc scales, SFR is related to H2 gas rather than HI
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Why are star formation relations interesting?

Extended ~ 10 pc scales low density ~ 102-103cm-3

1% 10 pc 1 kpc
Krumholz+10
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star formation (IR-CO) relations at high redshifts
Challenges: · Size measurements are difficult · CO-to-H2 gas mass conversion dubious

Extended ~ 10 pc scales low density ~ 10 -10 cm

· · · · ·

Greve+05 (12 SMGs + LIRGs): Iono+09 (SMGs+LIRGs, CO(3-2) only): Genzel+10 (10 SMGs + LIRGs): Bothwell+13 (>30 SMGs + LIRGs): 2 3 -3 Ivison+11 (SMGs+LIRGs, CO(1-0) only):

= = = = =

1.5 ± 0.3 1.10 ± 0.03 1.15 ± 0.12 1.20 ± 0.13 0.89 ± 0.04

· · · ·

Heterogenous samples Poorly sampled SEDs / LIR uncertain AGN contamination harder to assess Mixing J-transitions

1 kpc
Genzel+10

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star formation relations in the high density regime
12

CO J=1-0

Extended ~ 10 pc scales low density ~ 102-103cm-3

10 pc

1 kpc

Sunday, October 6, 2013


star formation relations in the high density regime

20 m

10 pc

1 kpc

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star formation relations in the high density regime

CS J=2-1

Compact ~ pc scales High density ~104-106cm-3

10 pc

1 kpc

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star formation relations in the high density regime

Critical density:

The CO ladder spans the full density regime encountered in the molecular ISM
CS(2-1) HCO+(1-0)

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LIR - Lmol models

CO(1-0)

HCN(1-0)

Krumholz & Thompson + 07
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star formation relations vs. critical density

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Observing the CO ladder in local (U)LIRGs
JCMT Herschel

A Ground-Based Multi-Line Survey of local (U)LIRGs 70 sources selected from IRAS BGS: CO 1-0, 2-1, 3-2, 4-3 HCN 1-0, 2-1, 3-2, 4-3 HCO+ 1-0 CS 2-1, 3-2, 5-4, 7-6

Molecular lines observed in Arp220

>350hrs of observing time. This is the largest multiline survey to date + literature data. Papadopoulso+12

· Full CO rotational ladder, dense+FIR lines · Comprehensive ISM characterization ! · Disentangling Starburst vs. AGN

Herschel Comprehensive (U)LIRG Emission Survey HERCULES (P.I.: van der Werf). 29 IRAS BGS sources CO 5-4 to 14-13 IRAM [CI] 369m and 609m H2O lines

ALMA

PdBI

Observed (100hrs). Van der Werf+10
Greve et al. (2009)
Sunday, October 6, 2013


Observing the CO ladder in local (U)LIRGs
JCMT Herschel

A Ground-Based Multi-Line Survey of local (U)LIRGs 70 sources selected from IRAS BGS: CO 1-0, 2-1, 3-2, 4-3 HCN 1-0, 2-1, 3-2, 4-3 HCO+ 1-0 CS 2-1, 3-2, 5-4, 7-6

>350hrs of observing time. This is the largest multiline survey to date + literature data. Papadopoulso+12

· Full CO rotational ladder, dense+FIR lines · Comprehensive ISM characterization ! · Disentangling Starburst vs. AGN

Herschel Comprehensive (U)LIRG Emission Survey HERCULES (P.I.: van der Werf). 29 IRAS BGS sources CO 5-4 to 14-13 IRAM [CI] 369m and 609m H2O lines

ALMA

PdBI

Van der Werf et al. (2010)
Sunday, October 6, 2013

Observed (100hrs). Van der Werf+10


Observing the CO ladder in local (U)LIRGs
JCMT Herschel

A Ground-Based Multi-Line Survey of local (U)LIRGs 70 sources selected from IRAS BGS: CO 1-0, 2-1, 3-2, 4-3 HCN 1-0, 2-1, 3-2, 4-3 HCO+ 1-0 CS 2-1, 3-2, 5-4, 7-6

>350hrs of observing time. This is the largest multiline survey to date + literature data. Papadopoulso+12

· Full CO rotational ladder, dense+FIR lines · Comprehensive ISM characterization ! · Disentangling Starburst vs. AGN

Herschel Comprehensive (U)LIRG Emission Survey HERCULES (P.I.: van der Werf). 29 IRAS BGS sources CO 5-4 to 14-13 IRAM [CI] 369m and 609m H2O lines

ALMA

PdBI

Observed (100hrs). Van der Werf+10
Sunday, October 6, 2013


Observing the CO ladder in local (U)LIRGs
IR luminosities · Careful compilation of pan-chromatic continuum data

· SED fitting performed using a modified CIGALE (Burgarella+05) code, which
employs Chary & Elbaz 2001 (CE01) and Dale & Helou 2002 (DH02) templates

· We adopt FIR (50-300m) luminosities (clean compared to 8-1000m)
Example SEDs:

Sunday, October 6, 2013


Observing the CO ladder in high-z (U)LIRGs
Dusty Star Forming Galaxies (DSFGs): · A compilation of all (sub)mm-selected z > 1 DSFGs with CO line detections
HERMES J105751.1+573027 z=2.95

· Obvious AGN discarded · Multiple observations of the same CO transition
were averaged, and intrinsic line luminosities recalculated

· A total of 58 unlensed DSFGs and 25 lensed
DSFGs (published as of Sep 2013)

· CIGALE fits, identical to local (U)LIRG fits · Only sources with >3 FIR/submm data
points across the dust peak, and with good CIGALE fits were included in the analysis

· Final sample: 23 unlensed DSFGs and
21 lensed DSFGs

Riechers+11
Sunday, October 6, 2013


Observing the CO ladder in high-z (U)LIRGs
Dusty Star Forming Galaxies (DSFGs): · A compilation of all (sub)mm-selected z > 1 DSFGs with CO line detections

· Obvious AGN discarded · Multiple observations of the same CO transition
were averaged, and intrinsic line luminosities recalculated

· A total of 58 unlensed DSFGs and 25 lensed
DSFGs (published as of Sep 2013)

· CIGALE fits, identical to local (U)LIRG fits · Only sources with >3 FIR/submm data
points across the dust peak, and with good CIGALE fits were included in the analysis

· Final sample: 23 unlensed DSFGs and
21 lensed DSFGs

Sunday, October 6, 2013


LIR-LCO relations

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LIR-LCO relations

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IR-mol slope vs. critical density

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IR-mol slope vs. critical density

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Interpretation of results
A simple theoretical argument can be made for why must always be 1 (Wong & Blitz 2002) We have

and so

slope of the IR-HCN(1-0) relation (1.00 ± 0.05; Gao & Solomon 2004)

dense gas fraction (expect to be at least as high at large LCO as at small LCO)

1
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IR-mol scatter vs. critical density

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Caveats
· · · ·
AGN contamination DSFGs are probably a mixed bag of objects (Haywards talk) Differential lensing may be an issue for the strongly lensed DSFGs Low-J / High-J ratio increases with n(H2) and Tk Degeneracy between n(H2) and Tk (since )

fixed: Tk = 60K

fixed: n(H2) = 104cm

-3

J
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up

J

up


CO SLEDs

Sunday, October 6, 2013