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ALMA and distant galaxies

ALMA and distant galaxies. Andrew Blain Caltech 5 th June 2006. AAS Meeting Calgary. Contents. ALMA will be a tremendously powerful transformational tool for all astrophysics 50 12-m antenna, with baselines from 15 to 20000m

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ALMA and distant galaxies

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  1. ALMA and distant galaxies Andrew Blain Caltech 5th June 2006 AAS Meeting Calgary

  2. Contents • ALMA will be a tremendously powerful transformational tool for all astrophysics • 50 12-m antenna, with baselines from 15 to 20000m • Resolution down to of order 10 m-arcsec (10-20x better than current) • Sensitivity of order 1mJy in 1s (30x better than existing arrays) • ALMA makes a day to minute integration time transformation • Field of view is antenna primary beam, of order 10-30 arcsec, so ALMA is unique for: • spectroscopic imaging of individual 1-5 arcsec scale galaxies • Ultradeep surveys (possible in parallel with deep pointed observations) • ALMA has Design Reference Science Plan (DRSP) giving an outline of possibilities (and demands on the program) for 3 years • http://www.strw.leidenuniv.nl/~alma/drsp.html • 40% of DRSP (10,500 hr ~ 14 months) is for extragalactic work • largest suggested programs were cut to meet the 3-year goal • 2000 hr of the extragalactic total is for local group and nearby AGN • GOODS, COSMOS… provide abundance of targets for 5-10 year ALMA’s program • What is ALMA’s unique role in studying galaxy evolution? • Resolution matched to HST/JWST; unlimited depth • Sensitivity to detect normal galaxies at z~3, & extremes prior to reionization • Full spectrum view of galaxy evolution

  3. ALMA’s Universe • Detail resolved so far only in Milky Way • ~50% of all AGN and starlight absorbed by dust • More in molecular star-forming regions • Dust cooling is crucial for Pop-I star formation • Extremely strong effect on visible morphology: ‘activity-light’ ratio • Dust present at z>6 • Combined with molecular gas rotational and atomic fine structure emission • Physics and chemistry of dust is complex and ill constrained • But, SED accessible through atmospheric windows is well known Orion through telephoto lens (~2 degree field)

  4. Observed far-IR/submm SEDs • Mix of different sources traces out some of the range of SEDs properties • Milky Way & APM08279 are extremes • Non-thermal radio • Radio-far-IR link • Thermal dust dominates luminosity • CO, HCN, HCO+, C fine structure lines carry redshift, dynamical, and physical information Normalized where sizeable sample of `submm galaxies’ are selected. Redshifts z~2-3 from Chapman et al.

  5. Resolved ‘example’: the Antennae ISOCAM 15m • Excellent example of distinct opt/UV and IR luminosity; BUT modest luminosity • Interaction long known, but great IRAS luminosity unexpected • ~90% energy escapes at far-IR wavelengths • Resolved images important • Relevant scales ~1” at high redshift CSO/SHARC-2 Dowell et al. 350m Spitzer IRAC mid-IR HST WFPC2 Multiband optical

  6. Distant galaxies at ALMA wavelengths • A significant population of very luminous high-redshift galaxies show powerful far-IR emission - submillimeter galaxies (SMGs) • Discovered at submm wavelengths (Smail et al 1997) • Most located by VLA in the radio, leading to redshifts from Keck optical spectra (Chapman et al 2003, 2005) • information fed back for detailed studies of gas using CO/H spectroscopy at millimeter/near-IR wavelengths using OVRO MMA, IRAM, Keck, Gemini, GBT… (Tacconi et al. 2006) • While the sample is relatively small (~100), they appear to be strongly clustered, and could be a valuable and efficient probe of high-redshift large-scale structure • There are signs of massive host galaxies • Stellar & dynamical masses from optical/IR images & mm/near-IR spectra • Aided by information from HST NICMOS & ACS morphologies to reduce uncertainties from color gradients / multiple components • Can they be connected with Spitzer-selected objects? • Yes, but their Spitzer colors have a large scatter • And with optically-selected galaxies? • Yes, but their luminosity functions do not yet overlap significantly • ALMA will provide a unified picture of the luminosity function of galaxies at high redshift

  7. Unique mm/submm access to highest z • Redshift the steep submm SED • Counteracts inverse square law dimming • Detect high-z galaxies as easily as those at z~0.5 • Low-z galaxies do not dominate submm images • Unique high-z access in mm and submm • Ultimate limit at z~10 is set by CMB heating • 2mJy at 1mm ~5x1012 Lo • Note matches current depth of submillimeter surveys • ALMA has no effective limit to depth

  8. Example of current single-antenna submm image • Abell 1835 • Hale 3-color optical • 850-micron SCUBA • Contrast: • Image resolution • Visible populations • Orthogonal submm and optical views • One of 7 images from Smail et al. SCUBA lens survey (97-02) • About 25 other SCUBA cluster images • Both bright sources have redshifts (2.5 and 2.3; Ivison et al. 2000 & G P Smith priv comm) Ivison et al. (2000) 2.5’ square

  9. Population of dusty galaxies • Most data is at 850 µm • New bright limit from Barnard et al (0405156) • Very few are Galactic contaminating clouds • First 2.8mm limit from BIMA • Bright 95 (&175) µm counts from ISO being dramatically improved at 70 & 160 µm by Spitzer (started August 04 ApJS) • Also recent data at 1.2mm (IRAM’s MAMBO); 1.1mm (CSO’s BOLOCAM) and 350/450µm (SCUBA & SHARC-2) * * * Orange stars – Barnard et al (2004) 850-µm upper limits

  10. Obscured galaxies: background • Many sources of data • Total far-IR and optical background intensity comparable • Most of the submm (0.8mm) background was detected by SCUBA • ISO and more precise (but similar) Spitzer limits detect ~20-30% in mid-IR • Note: backgrounds yield weaker constraints on evolution than counts Spitzer MIPS/IRAC ISO SCUBA SCUBA Model: BJSLKI ‘ Models: BJSLKI 99

  11. Redshift distribution N(z) for radio-pinpointed SMGs • Red histogram: Chapman et al • Lines: expected submm & radio N(z)’s from Chapman’s model • Consistent with early submm-derived Madau plots but result is now MUCH more robust • Magenta shade at z~1.5 is ‘spectroscopic desert’: rest-UV & rest-optical lines both hard to observe • Blue shading at highest z is incompleteness due to radio non-detection. Likely modest, but uncertain • Now 73 redshifts (ApJ 2005) • Median z=2.4 and spread in redshift z~0.65 is good description Chapman et al. (2003; 2005)

  12. Global luminosity evolution • Points • Blue: optical / UV • Red: IR and dust corrected • Black: SDSS fossil record • Uncertainty remains • Lines: • results from combined submm/far-IR information • Note high-z decline certain • Less rapid than for QSOs? • Caveats • AGN power (modest?) • High-z / high-L IMF change • Submm-selected sample probes most intense epoch of galaxy evolution directly WMAP cosmology

  13. Example IDed submm galaxy 6”x6” 20”x20” Narrow band Ivison et al (2000, 2001); Swinbank et al. (2004) • Relatively bright, complex example • May not see most important region in the optical - Spitzer IRAC can highlight interesting locations • J2 is a Lyman-break galaxy (Adelberger & Steidel 2000) • J1 is a cluster member post-starburst galaxy (Tecza et al. 2004) • H/continuum ratio imply this does not add significant magnification • J1n is an Extremely Red Object (ERO; Ivison 2001) • Remains red in deeper Keck-NIRC data • Powerful H emission • Both J1n & J2 are at z = 2.55 – radio and mm appear to be from J1n

  14. Best achievable now - distant • Only marginal spatial resolution possible • Spectral bandwidth narrow • Situation will improve dramatically with ALMA, a step in imaging quality tested at CARMA & IRAM Genzel et al PdB 8’x8’ field PdB HCO+(5-4) Garica-Burillo et al (2006)

  15. Local example of best results • IRAM PdB CO in NGC 6946 (Schinner et al. 2006) • Spatial structure & gas dynamics • ALMA can probe at z~3 • Resolution • Primary beam • Note synergy with eVLA • Ultimately SKA CO(2-1) contours HST: Pa & I band Red: CO; green: H; blue: continuum CO(2-1) CO(1-0)

  16. Comparison with other populations • Other more numerous high-z populations have less powerful clustering • Are SMG redshift associations linked to overdensities of more numerous galaxy classes at the same redshift? • At z~2.5 spectroscopy essential to test • Links with ‘BX’ optically selected galaxies at z~2 in HDF • Narrow-band imaging with LRIS in March to search for associated optical galaxies • Do they reside in such massive halos? • Not every 10’ field can contain such an object • What is the nature of the biasing process? • Near-IR spectra hint at central 4-kpc dynamical masses of few 1011Mo • Stellar population fitting implies few 1010Mo,but uncertainties from complex morphology • OSIRIS resolved spectra will be exciting After Overzier et al. (2003)

  17. SMGs have a wide range of multiwavelength properties • To better probe their nature, cause and descendents need larger samples and more powerful tools • Deeper and wider surveys (CCAT) • Efficient spectrographs at mm/submm/IR wavelengths to augment optical line work (ALMA) • Goals are to • Link optical and submm populations together • Understand environmental factors

  18. ALMA cosmolgy: imaging of clusters Red: cluster members Blue: background galaxies Also diffuse SZ effect • Excellent probes of clusters’ strong lensing when ALMA’s angular resolution is available A2218 HST & Keck-ESI Einstein radius for z~2 Einstein radius for z~2 Very faint z=5.5 object shows what can be seen along high-magnification critical lines in all clusters Simulation shows some of the swarm of faint sources expected in the cluster centre if the potential strongly peaked

  19. Other (near-) future tools   See also Spitzer & Akari *-shown CARMA*, APEX*, SOFIA*, SCUBA-II, LMT, Herschel*, Planck*, WISE*, ALMA*, CCAT*, SPICA, SAFIR (JWST-based?)* SPECS/SPIRIT

  20. Summary • ALMA will provide spectral and spatial resolution to image regions of galaxies where stars are forming and blackholes are fueling most intensely at z~2-3 • Galaxies can be studied from z=0.1 to beyond reionization • Spectral data will allow unprecedented accuracy for derived dynamical masses • Detailed pre-reionization science • Exploiting gravitational telescopes

  21. Near-IR spectroscopy (NIRSPEC, VLT and narrow-band at IRTF & UKIRT) • 25 targeted • Optical redshifts allow near-IR spectroscopy in favorable sky windows • H/[NII] ratios and H line widths provide hints at presence of AGN • Composite spectrum of examples with narrow (<400km/s) H show underlying broad line; narrow component gives dynamical mass - few 1011 Mo • Adding [OII]/[OIII] ratios could bring in metallicity, but very time consuming! • Aim to target brightest examples with OSIRIS to measure detailed dynamics Swinbank et al. 2004

  22. CCAT: Speed vs other instruments • ALMA, SCUBA-2, 50-m LMT, Herschel • Assume CCAT cameras • 1100, 870, 740, 620, 450, 350, 200 microns • SWCAM 32000 pixels • LWCAM 16000 pixels • Fastest depth ~few mJy at 1100 microns • FOV 25 arcmin2 • 1mJy 5σ in 30s • 1/2-sky survey in 2.5 yr • 108 galaxies • Confusion limited (350micron) • 0.05mJy 1σ in 600s • 2 deg2 in 40hr • 106 galaxies over few yr • Huge galaxy surveys • CMB foreground maps

  23. Overcoming confusion • Current missions in black • Spitzer is + • Green bar is just a 500m baseline ALMA • Purple bar is ground-based 25-m CCAT • Red bar is 10-m SAFIR • Confusion from galaxies not met for many minutes or hours • At shortest wavelengths very deep observations are possible • Factor 2 increase in resolution over existing facilities is very powerful • Submm confusion dives at 5” ▬ ▬ ▬

  24. X-ray reveals AGN in 2-Ms HDF • 2-Ms exposure reaches 1% of typical QSO X-ray flux at z~2.5 • X-ray flux of SMGs implies significant AGN power Alexander et al. (2005a,b) 19 galaxies in GOODS-N field Redshifts allow stacking in soft & hard classes Excellent fit to X-ray SED models - Fe emission & H absorption

  25. SMGs with z’s: FIR-radio assumed Squares: low-z, Dunne et al. Empty circles: moderate z, mainly Stanford et al. Crosses: variety of known redshifts (vertical = lensed) Solid circles: Chapman SMGs Lines: low-z trends Scatter in T by at least ~40% Radio loud caveat above ~60K Solid circles: new Submm sources Blain, Barnard & Chapman 2003 & Chapman et al. 2003

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