ALMA and distant galaxies

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ALMA and distant galaxies

• Andrew Blain
• Caltech
• 5th June 2006

AAS Meeting Calgary
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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 ALMAs program
• What is ALMAs unique role in studying galaxy
  evolution?
• Resolution matched to HST/JWST unlimited depth
• Sensitivity to detect normal galaxies at z3,
  extremes prior to reionization

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ALMAs 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 zgt6
• 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)
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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 z2-3 from
Chapman et al.
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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
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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

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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
  z0.5
• Low-z galaxies do not dominate submm images
• Unique high-z access in mm and submm
• Ultimate limit at z10 is set by CMB heating
• 2mJy at 1mm 5x1012 Lo
• Note matches current depth of submillimeter
  surveys
• ALMA has no effective limit to depth

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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
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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 (IRAMs MAMBO) 1.1mm
  (CSOs BOLOCAM) and 350/450µm (SCUBA SHARC-2)

Orange stars Barnard et al (2004) 850-µm upper
limits
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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
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Redshift distribution N(z) for radio-pinpointed
SMGs

• Red histogram Chapman et al
• Lines expected submm radio N(z)s from
  Chapmans model
• Consistent with early submm-derived Madau plots
  but result is now MUCH more robust
• Magenta shade at z1.5 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 z2.4 and spread in redshift z0.65 is
  good description

Chapman et al. (2003 2005)
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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
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Example IDed submm galaxy
6x6
20x20
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

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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
8x8 field PdB HCO(5-4) Garica-Burillo et al
(2006)
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Local example of best results

• IRAM PdB CO in NGC 6946 (Schinner et al. 2006)
• Spatial structure gas dynamics
• ALMA can probe at z3
• 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)
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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 z2.5 spectroscopy essential to test
• Links with BX optically selected galaxies at
  z2 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)
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• 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

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ALMA cosmolgy imaging of clusters
Red cluster members Blue background
galaxies Also diffuse SZ effect
A2218 HST Keck-ESI
Einstein radius for z2
Einstein radius for z2
Very faint z5.5 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

• Excellent probes of clusters strong lensing when
  ALMAs angular resolution is available

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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
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Summary

• ALMA will provide spectral and spatial resolution
  to image regions of galaxies where stars are
  forming and blackholes are fueling most intensely
  at z2-3
• Galaxies can be studied from z0.1 to beyond
  reionization
• Spectral data will allow unprecedented accuracy
  for derived dynamical masses
• Detailed pre-reionization science
• Exploiting gravitational telescopes

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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
  (lt400km/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
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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 5s in 30s
• 1/2-sky survey in 2.5 yr
• 108 galaxies
• Confusion limited (350micron)
• 0.05mJy 1s in 600s
• 2 deg2 in 40hr
• 106 galaxies over few yr
• Huge galaxy surveys
• CMB foreground maps

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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

?
?
?
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X-ray reveals AGN in 2-Ms HDF

• 2-Ms exposure reaches 1 of typical QSO X-ray
  flux at z2.5
• 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
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SMGs with zs 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