blainalma

Galaxies and cosmology: the promise of ALMA: 

Galaxies and cosmology: the promise of ALMA Andrew Blain Caltech 14th May 2004 ALMA North American Workshop

Contents: 

Contents CMB and SZ – cosmology aspect Examples of what we know ALMA can see Sub-arcsec resolution microJy sensitivities No confusion noise Continuum and line surveys Advances over all existing/proposed capabilities Sensitivity is not infinite! Relatively small field of view

Fine angular scale CMB and SZ: 

Fine angular scale CMB and SZ ALMA (with compact array) will be extremely sensitive to arcmin-scale CMB power, from clusters, filaments and primordial fluctuations Carlstrom et al. Arcmin resolution Fine resolution will reveal features in the intracluster medium to resolve physical conditions in cluster gas ALMA X-ray SZ effect Chandra – low-z Hydra cluster with substructure

Slide4: 

Example target: the Antennae Excellent example of distinct opt/UV and IR luminosity Interaction long known, but great luminosity unexpected ~90% energy escapes at far-IR wavelengths Resolved images important Relevant scales ~1' at high redshift HST WFPC2 ISOCAM CSO/SHARC-2 Dowell et al.

Observed far-IR/submm SEDs: 

Observed far-IR/submm SEDs Non-thermal radio Thermal dust Dominates luminosity Hotter in AGN? See Spitzer Molecular and atomic lines Mm CO / HCN IR: C/N/O/H2 IR: C=C PAH

Slide6: 

Submm population: backgrounds Many sources of data Total far-IR and optical background intensity comparable Most of submm background detected by SCUBA Backgrounds yield weaker constraints on evolution than counts SCUBA ISO Model: BJSLKI ‘ Models: BJSLKI 99 SCUBA

ALMA will resolve the most distant galaxies down to L*: 

ALMA will resolve the most distant galaxies down to L* Example objects known from existing ground based observations High-redshift continuum emission Marginally resolved CO spectra reveal internal structure, and dynamical masses Spitzer will reveal a huge sample to follow up Redshifts are ‘moderate’ z~2-3 ALMA will see CO structure in detail ALMA will probe fainter, still unconfused

Example Deep Submm Image: 

Example Deep 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 SCUBA cluster images Ivison et al. (2000) 2.5’ square

Example IDed submm galaxy: 

Example IDed submm galaxy Unusually bright example May not see most important region in the optical J2 is a Lyman-break galaxy (Adelberger andamp; Steidel 2000) J1 is a cluster member post-starburst (Tecza et al. 2004) J1n is an Extremely Red Object (ERO; Ivison 2001) Remains red in deeper Keck-NIRC data Both J1n andamp; J2 are at z = 2.55 – radio and mm from J1n Ivison et al (2000, 2001)

High-redshift CO: 

High-redshift CO K band image (8' square), with IRAM CO contours of an ultraluminous galaxy at z=3.35 Genzel et al. (2004) Abell 2218 ISO 15µm and optical image (2.5’ across); Metcalf et al. Orange – left image Red – bottom image SAFIR field exceeds extent of the ISO image, yet has spatial resolution as good as the inteferometer, plus spectral information  Upper: submm continuum; lower optical HST | | | | Note: submm, optical and mid-IR show different populations 40' square Abell 851

Submm galaxies in CO(3-2),(4-3): 

Submm galaxies in CO(3-2),(4-3) Neri et al. ApJ (2003); IRAM interferometer; source of detections given on individual frames 8 more now have CO measurements Frayer et al. N4 Smail et al. N2.4 Chapman et al.

Population of submm galaxies: 

Population of submm galaxies Most data is at 850 µm New bright limit from Barnard et al Very few are Galactic contaminating clouds First limit was at 2.8 mm (BIMA) Also bright 95/175 µm counts (ISO), that will be dramatically improved by Spitzer Also data at 1.2mm (MAMBO); 1.1mm (BOLOCAM) and 450µm Blain et al (2002) updated Orange stars – Barnard et al (2004) 850-µm upper limit * * *

Unique submm access to highest z: 

Unique 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 Low-z galaxies do not dominate submm images Unique high-z access in mm and submm Ultimate limit is CMB heating

Existing limits to information: 

Existing limits to information Limited few arcsec positional accuracy from 10-m class submm telescopes challenges accurate identification and makes it difficult to target for spectroscopy So far VLA radio positions required for spectroscopy Optical spectroscopy has provided redshifts for more of this population that might have been expected (Chapman et al 2003; 2004) ALMA will not be limited in this way To only cooler, more luminous, lower redshift systems

850-µm redshift distribution: 

850-µm redshift distribution Histogram: sample expanded from Nature list Expected submm andamp; radio redshift distributions from Scott Chapman’s model Consistent with studeis of star-formation history that show far-IR domiates optical at z~2, but result now MUCH more robust z~1.5 gap is the ‘spectroscopic desert’ Bias against highest z is likely modest, but still uncertain Chapman et al. (2003; Nature; 2004; ApJ subm.)

Signs of large-scale structure: 

Signs of large-scale structure HDF-N/GOODS field submm/radio spectroscopic survey (Chapman et al 2004) Geometry is extreme pencil beam 5 x 3000 Mpc Same for ALMA Circles: all galaxies with redshifts Empty: z known Colored: z in ‘associations’ within 1200 km/s Note more ‘associations’ than expected unless powerful galaxy-galaxy correlation r0 ~ 7h-1 Mpc ALMA will resolve less luminous associated structure and map the regions in detail Blain et al. (astro-ph/0405035)

ALMA’s resolution puts it ahead: 

ALMA’s resolution puts it ahead Resolution is very fine, both to avoid confusion from overlapping sources, and resolve their internal structure The second absolutely demands ALMA The first can also be achieved by large aperture single-antenna telescopes on the ground and in space These can provide wide-field finder images 25-m submm ‘Atacama Telescope’ Cornell-Caltech study

Confusion noise: 

Confusion noise Model based on SCUBA/ISO populations Flux for 1 source per beam ~ RMS noise Extragalactic sources dominate for small apertures When andlt; 500µm ~25-m aperture very important andlt;0.1mJy sure to find submm counterparts to high-z optical galaxies

Time to reach confusion limit: 

Time to reach confusion limit Galactic andamp; extragalactic confusion limits Sensitivity α D-1 Practical limit ~10-100hr in any field At shortest wavelengths need large aperture to allow deep surveys Note speed at 850µm 9' resolution

Confusion is avoided with ALMA: 

Confusion is avoided with ALMA Current missions in black Spitzer is +\ Green bar is just a 500m baseline ALMA 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 of 10 in resolution over existing facilities is very powerful ▬ ▬

Submm observations of galaxies mature in ALMA era: 

Submm observations of galaxies mature in ALMA era Resolution to match HST/JWST and resolve internal structure of high-z galaxies 3-D spectral information of even the most obscured regions Reveals astrophysics at work Provides direct redshifts ALMA astrophysical probes are self contained New populations of objects, and pre-reionization galaxies H2 lines / first metals – dust and fine-structure lines

‘Photometric redshifts’: 

‘Photometric redshifts’ Combine different bands to estimate T andamp; z together No strong far-IR spectral breaks or features Strongest lever from 200-600µm Based on knowledge of galaxies/site, can probably design 2 optimal bands Once z known, get accurate luminosity ALMA can do this, but combined with real redshift information from spectra

SMGs’ SEDs: FIR-radio assumed: 

SMGs’ SEDs: FIR-radio assumed Blain, Barnard andamp; Chapman 2003; Blain et al (2004; astro-ph/0404438) Solid circles: new Submm sources Radio loud caveat above ~60K 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 andgt;~40% ALMA can explore new region here ALMA can explore new region here

Line emission: 

Line emission Optical spectroscopy will probably never be able to keep up with mid-IR discoveries Especially the ‘hard cases’, deeply enshrouded in dust at zandgt;5 Far-IR emission lines and CO rotational emission reveal astrophysics of gas involved in star formation Heterodyne Randgt;106 and 8-GHz bandwidth: ALMA can see details ALMA can make spatially andamp; spectrally resolved images of the most interesting galaxies found in andlt;1hr Little information on far-IR lines available so far SOFIA will test this science Spitzer covers restframe spectra of low-redshift galaxies CII and OI pair can give redshifts for z~4.5; CO may be exhausted / not excited / not present at these redshifts High redshift AGN andamp; LBGs show metallicities are high early on

Lines available for detection: 

Lines available for detection Left: 870µm window; 5x10-21 Wm-2 (10-σ 18 min) Right: 350µm window; 4-10x10-20 Wm-2 (10-σ 8.7 hr) Long wavelength – in blind searches detect ~ 1 hour -1 ALMA is fastest planned instrument working at longer wavelengths Gives resolved spectroscopy – redshift and dynamical information

Summary : 

Summary ALMA will detect huge numbers of galaxies, deeper than any other facility Probe astrophysics during most active phase at z~2-3 Prior to re-ionization Resolved spectral images will reveal masses and mass assembly of galaxies DRSM shows demand will be high All areas of extragalactic astrophysics will benefit from ALMA