1 / 27

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

crete
Download Presentation

ALMA and distant galaxies

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  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

More Related