The ISM in z~2.5 starbursting galaxies: dust, synchrotron emission and cold molecular gas Alasdair Thomson Ian Smail, Mark Swinbank, Rob Ivison, Jacqueline Hodge, Alex Karim James Simpson, Alice Danielson, Fabian Walter, Frazer Owen ++ ALESS consortium

Outline Submillimetre galaxies The ALMA LESS survey Survey overview Far-IR properties of ALESS SMGs The radio properties of ALESS SMGs Trends in α and qIR in starbursting galaxies The Cosmic Eyelash – a “Rosetta Stone” for the high-z ISM Identification of ~100pc gas clumps in lensed, z~2.3 ISM Spatially-resolved gas excitation and star-formation law

Submillimetre-selected galaxies Rest-frame SEDs peak in the far-IR due to dust-reprocessing of optical/UV starlight <z> ~ 2.5 - can be detected out to z~7 due to negative K-correction (Ultra-) luminous: LIR ≥ 1012 Lʘ Massive: M* ≥ 1011 Mʘ SFR ~ 200 – 1000 Mʘyr-1

The LABOCA Extended Chandra Deep Field South Survey (LESS: Weiss et al ECDFS is the prime extra-galactic survey field, with a wealth of pan-chromatic data from X-ray (Chandra), through UV/optical/mid-IR (Subaru, VLT, Spitzer IRAC), far-IR (Herschel SPIRE) and radio (VLA) LESS is a contiguous and uniform 870-μm survey reaching S870=1.2mJy over ~30x30' 126 SMGs with S850 > 4.4mJy APEX LABOCA 870-μm map However λ/D~18”, so counterpart identifcation potentially tricky...

The ALMA LABOCA Extended Chandra Deep Field South Survey (ALESS: Hodge et al. 2013/Karim et al. 2013) LABOCA ~ 18” ALMA ~ 1.4” 122 ALMA pointings to observe 122 LABOCA SMGs ALMA maps ~3x deeper, with ~200x smaller beam than LABOCA 88 best (“MAIN”) maps have σ < 0.6mJy/beam and beam axis ratio < 2 In 69 maps, we detect 99 ALMA sources at >3.5σ (multiplicity) with 18 blank maps (20%) - Spurious LABOCA detections? Diffuse emission spread across multiple ALMA beams? Extreme multiplicity? ?

An ALMA survey of submillimetre galaxies in the Extended Chandra Deep Field South: the far-IR properties of SMGs (Swinbank et al. 2013) To properly characterise far-IR SED, need measurements over the dust peak (160-500μm)... ...but Herschel SPIRE resolution ~15” at 250μm (35” at 500μm) → need to deblend SPIRE photometry Swinbank et al. (2013)

An ALMA survey of submillimetre galaxies in the Extended Chandra Deep Field South: the far-IR properties of SMGs (Swinbank et al. 2013)

An ALMA survey of submillimetre galaxies in the Extended Chandra Deep Field South: redshift distribution (Simpson et al. 2013) ECDFS deep archival imaging: UBVRIzJHK+IRAC Of 99 “MAIN” ALMA SMGs, 77 have good photometry in enough bands to determine reliable phot-z's Calibrated against 5,900 field galaxies in ECDFS ~25 SMGs with spec-z's <zphot> = 2.3 ± 0.1 Tail out to z~6 Simpson et al. (2013)

An ALMA survey of submillimetre galaxies in the Extended Chandra Deep Field South: radio properties and FIRRC (Thomson et al. 2014) Detect 52 SMGs at > 3σ in VLA 1.4 GHz map (Miller et al. 2013) Of which 35 detected at > 3σ in GMRT 610 MHz map (Rob Ivison) SMGs with counterparts in both radio maps: <α> = -0.79 ± 0.06 Sυ ~ υα SMGs with counterparts in VLA map only (stacked): <α> = -0.76 ± 0.06 cf. Lockman Hole SMGs (Ibar et al. 2010): <α> = -0.75 ± 0.06 Condon, 1992

An ALMA survey of submillimetre galaxies in the Extended Chandra Deep Field South: radio properties and FIRRC (Thomson et al. 2014) Background – Spitzer IRAC 4.5μm Red – ALMA 870μm (ALESS: σ = 0.3 mJy/beam) Blue – GMRT 610 MHz: σ = 45 μJy/beam (Rob Ivison) Green – VLA 1.4 GHz: σ = 7 μJy/beam (Miller et al. 2013)

An ALMA survey of submillimetre galaxies in the Extended Chandra Deep Field South: radio properties and FIRRC (Thomson et al. 2014) Tight empirical correlation between rest-frame far-IR/radio luminosities in star-forming regions over orders of magnitude in size/luminosity/gas surface density/magnetic energy density Thought to arise due to a balance between thermal dust and synchrotron emission of massive stars <qIR> = 2.56 ± 0.05 cf. <qIR> = 2.40 ± 0.12 for 0<z<2 Herschel 250μm selected galaxies (Ivison 10a,10b) De Jong (1985)

An ALMA survey of submillimetre galaxies in the Extended Chandra Deep Field South: radio properties and FIRRC (Thomson et al. 2014) Evolution of α and qIR? Bressan et al. (2002) Condon (1992)

An ALMA survey of submillimetre galaxies in the Extended Chandra Deep Field South: radio properties and FIRRC (Thomson et al. 2014) Evolution of α and qIR? Young: M⋆ = (0.84± 0.27) × 1011M⊙ Middle-aged: M⋆= (1.02 ± 0.28) × 1011M⊙ Old: M⋆ = (2.12 ± 0.64) × 1011M⊙

An ALMA survey of submillimetre galaxies in the Extended Chandra Deep Field South - papers 1. Catalogue paper + Multiplicity (Hodge et al. 2013, ApJ 768 91) 2. High resolution sub-mm counts. Influence of blending on counts (Karim et al. 2013, MNRAS 432 2). 3. Serendipitous z=4.4 [CII] identification & the evolution of the [CII] LF (Swinbank et al. 2012, MNRAS 427 1066) 4. OI 63-um detections in ALMA SMGs (Coppin et al. 2012, MNRAS 427 520) 5. N(z), stellar masses and evolution to z=0 (Simpson et al. 2014 ApJ 788 125) 6. FIR colours, luminosities, SFRs (Swinbank et al. 2014 MNRAS 438 1267) 7. AGN fraction of ALESS SMGs (Wang et al. 2013 ApJ 179 25) 8. Sub-mm properties of star forming BzKs and BX/BMs from ALMA (Decarli et al. 2014 ApJ 780 115) 9. FIR--radio correlation of ALESS SMGs (Thomson et al. 2014 MNRAS 442 577) 10. Energy balance in ALESS SMGs (E da Cunha et al. 2015 ApJ, Submitted) 11. The rest-frame optical morphologies of ALESS SMGs from HST (Chen et al. 2015, ApJ 799 194) 12. zLESS: The redshift distribution and star formation histories of ALESS SMGs (Danielson et al. 2015 in prep)

The Cosmic Eyelash – a “Rosetta Stone” for the high-z ISM Typical high-resolution ALMA Cycle 2 870μm images ~ 0.3” (e.g. Simpson et al 2015, in prep) → corresponds to a spatial scale of ~2.5kpc at z=2.3, 30x coarser than needed to study Giant Molecular Cloud complexes in which star formation likely to be concentrated “Eyelash” SMG discovered by LABOCA behind critical curve of MACSJ2135 cluster ~32x gravitational lensing boosts spatial resolution in the image plane to ~100pc Swinbank et al (2011)

The Cosmic Eyelash – a “Rosetta Stone” for the high-z ISM Danielson et al (2011, 13)

The Cosmic Eyelash – a “Rosetta Stone” for the high-z ISM Gas clump positions identified via two independent methods, using 3D data cube (position, position, velocity): (I) “ClumpFind” algorithm (Williams, 1994); (ii) AIPS task SERCH (e.g. Uson et al) Only clumps identified via both methods are considered → 4 bright clumps (plus 4 mirror images across critical curve) found Thomson et al (2015) CHECK: positions/velocities of clumps consistent with source-integrated line profile High-res VLA CO(1-0) and C-band continuum observations, plus re-imaging of existing SMA 870μm visibilities reveal dense, gas-rich, clumpy ISM .

The Cosmic Eyelash – clump excitation properties Measure CO SLEDs for the clumps using high-resolution CO(1-0) image, and “deblended” low-resolution mid-J images from PdBI (Danielson et al, 2011) Model predictions from ΣSFR (Narayanan & Krumholz, 2014; grey band) agree with best-fit radiative transfer model (solid line) in ¾ clumps.

The Cosmic Eyelash – clump properties

Conclusions Submillimetre galaxies are a population of intensely star-forming galaxies at high-redshift Single-dish only studies lack the angular resolution to precisely locate the starburst, requiring probabilistic counterpart identification techniques that assume the underlying SED ALMA follow-up observations of single-dish detected sub-mm sources circumvents identification problem by precisely locating the SMG in the same band as was used to select the source. Allows us to study radio properties of a complete, unbiased SMG sample: <α> = 0.79 ± 0.06 and <q> = 2.56 ± 0.05 Measured α, q and M* consistent with starburst galaxy evolutionary models which suggest radio observations can be useful probes of the phase of galaxy evolution Gravitational lensing still has a role to play, boosting spatial resolution and allowing us to peer inside the ISM of distant, starbursting galaxies The Eyelash SMG (z=2.3) is a “standard” but 32.5x lensed SMG, where 0.3” JVLA CO imaging isolates ~100pc clumps Observations provide an excellent laboratory for the study of dense, high ΣSFR starburst environments ...but still can't definitively rule on nature of high-z, high-ΣSFR SF law!