qCOSMOS Team Meeting ‘10 | June 10, 2010

The ISM PropertiesProperties of distant star-forming galaxies as constrained by the parameter

(in its various guises)

M. Sargent (MPIA) & you

I. update on the (on-going) IR-radio relation work

II. disk galaxy opacity at z ~ 0.7

III. final VLA-COSMOS Joint Catalog

I. update on the (on-going) IR-radio relation work

II. disk galaxy opacity at z ~ 0.7

III. final VLA-COSMOS Joint Catalog

June 3, 2010

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Intro

Radio & 60 m luminosity functions of galaxies in the IRAS 2 Jy-sample (Yun+ ‘01):

starbursts

field galaxies

‘monsters’

Common link due to life cycle of massive stars:

Non-thermal radio (synchrotron) emission and, in the IR, re-radiated UV light.

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q = log(SIR/Sradio)q = log(SIR/Sradio)

1.5 kpc regions in individual SINGS galaxies (Murphy+ ‘06) … and the transition to integrated IR/radio flux ratios (Yun+ ‘01)

Intro - local galaxies (II)

log(FIR flux [Wm-2])

log(1.4 GHz flux [mJy]) radio-loud AGN

‘regular’star-forminggalaxies

nascentstarbursts

Early IRAS results, integratedIR/radio flux (Helou+ ‘85) :

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Intro - Reasons to study the evolution• Calibration of radio continuum emission as a star formation tracer in distant galaxies (see Alex’ talk!)

• Does or doesn’t the IR-radio relation evolve with redshift (see somewhat ambiguous results in the literature) ?

• Changes in the correlation due to (understandable) external factors could shed light on:

- the physical processes shaping the relation (also at low-z)

- state of the ISM (magnetic fields, intensity of UV radiation field, dust absorption)

• “…for the […] galaxies studied here, luminosity extrapolations basedon the radio emission are considerably more reliable than thosebased on the mid-IR emission” (Magnelli+ ‘10)

- the calculation of SFRs is affected less by uncertain radio

spectral indices than by a sparsely sampled IR-SED

- interferometric radio observations have a high spatial

resolution, aiding the correct identification and attribution of

flux to (multi-) counterparts

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Evolution of the brightest IR-emitters

• volume-limited sample of ULIRGs (rather than comparing most strongly starbursting systems at high z with mixture of high & low luminosity systems at low z)

• IR/radio non-detections included with survival analysis

• probabilistic (using rest-frame optical colours) classification into SFGs/AGN (cf. Smolčić+ ‘08)

redshift

median

〈qTIR〉

ULIRGs:

LIR > 1012 L☉

SFR > 100 M☉/yr

After compensating for selection biases - NO evolution at z < 2

(implies B ~ 50 G).

〈 qTIR ∝ 〉 (1+z)-0.01±0.06〈 qTIR ∝ 〉 (1+z)-0.01±0.06

Sargent+ (‘10b)

•1.4 GHz image stacks of reach rms noise of ~400 nJy thanks to 100s

of sources in each mass/redshift bin -> statistical detections of

LIRG luminosities out to z ~ 3

• Sample based on 3.6 m IRAC detections in COSMOS field (cf. Sanders+ ‘07, Ilbert+ ‘09)

-> expect unbiased estimate of average IR/radio ratios (as sample not IR- or radio-selected)

• Actively star forming galaxies selected with (NUV-r) colours (cf. Ilbert+ ‘09)

Evolution of less extreme starbursts

increasingstellar mass

No differing behaviour between stacked and high(er) luminosity samples!

normalization of starburst template SEDs adopted from direct detections

redshift

q70, obs.

Expected evolution of q70 for galaxies with IR dust SEDs similar to local galaxies

Sargent+ (‘10d), in prog.

Alex’ hard work

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Other IR/radio miscellanea… (Sargent+

‘10a)

〈 q〉 IR-sel. > 〈 q〉 radio-sel.

〈 q〉 IR-sel. > 〈 q〉 radio-sel.

Analytical prediction of offset between IR- and radio-selected samples, qbias = ln(10) [-1] 2,

(e.g. Kellermann ‘64; Condon ‘84) can reconcile discrepancies in the literature.

➠At z < 1.5: many (optically classified) AGN have the same IR/radio ratios as star-forming galaxies.

➠

➠At 2.5 < z < 5: 〈 qTIR 〉 = 2.71+0.09, consistent with local average.

-0.14

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The Effects of Dust…Parametrization of average variation of surface brightness with inclination due to dust attenuation:

Driver+ (‘07)

opacityincrease

surface bright-ness increase

z~0.7

z~0

Sargent+ (‘10c)

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QuickTime™ and a decompressor

are needed to see this picture.

q = b/a

1 - cosine(inclination angle)

blue-band surface brightness

Attenuation vs. inclination

‘real’ distant disk galaxiesredshifted local disk galaxies

brighter

face-on

edge-on

• low-z reference galaxies (from Kampczyk+ ‘07) show expected (cf. Möllenhoff+ ‘06; Driver+ ‘07) surface brightness variations also once redshifted; distant galactic disks behave as if (nearly perfectly!) optically thick…

At z~0.7: less

va-riation between the average sur-face brightness of face-on and edge-on, large disk galaxies.

• Scant evidence for different extinction laws in distant galaxies (e.g., Calzetti+ ‘01; Conroy+ ‘10), a different distribution of attenuating material seems a likely explanation

• Correction relative to face-on ‘homogenizes’ population but does not provide the re-sidual face-on attenuation ➠ interpret shape of inclination-dependence with dust models

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Summary

Evolution of the IR-radio relation:• No compelling evidence for an evolution of the IR-radio relation out to high redshift, also in luminosity ranges in which the observation of evolution would not have been a surprise…

• The understanding/awareness of selection effects is essential for the derivation of the correct (non-)evolution

• Many optically-selected AGN at z < 1 have similar IR/radio ratios as star forming galaxies

Inclination-dependent attenuation in disk

galaxies at z ~ 0.7:

• Blue light escapes high- and low-z disk galaxies with a different (3D-)angular emission pattern, suggesting a different distribution of attenuating material

Plus…:• final VLA-COMOS Joint (source catalog from survey components ‘Large’ & ‘Deep’) catalog is available @ IRSA and published as Schinnerer+ ‘10, ApJS, 188, 384

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Final VLA-COSMOS Joint catalog(irsa.ipac.caltech.edu/data/COSMOS/tables/vla/……vla-cosmos_dp_sources_20100504.tbl)

• central 1 deg2 (seven pointings) re-imaged for additional 8.3 hr each

• 2865 sources with S/N > 5

• 1.4 GHz maps @ resolution 1.5” & 2.5” available

• rms at field centre ~10

Jy• 1/3 spectroscopically followed-up (pre 20k)

• catalog paper accepted to ApJS

rms ~30 Jy

• Counterpart searches ➠ use new Joint catalog• Statistical studies requiring flux-limited samples ➠ use revised Large

Project catalog