Title: 36th Lige International Astrophysical Colloquium: From Optical to Millimetric Interferometry Extraga
1Extragalactic Observations with ALMA
Tommy Wiklind Astronomy Astrophysics, Onsala
Space Observatory, Sweden
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
2Outline
- Introduction and background
- The ALMA instrument
- Galaxies in the nearby universe
- Galaxies at intermediate redshift
- Galaxies at high redshift
- Dust continuum emission
- CO line emission
- Atomic fine structure lines
- Molecular absorption lines
- Gravitational lensing
- Surveys
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
3Extragalactic astronomy
- Nearest neighbour (the Magellanic Clouds) at 55
kpc - (180 000 light years)
- Most distant galaxies at z 6 (look-back time
95 of the age of the universe) - (12 billion light years)
Hubble Deep Field South
Large Magellanic Cloud (55kpc)
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
436th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
5The most distant CO and dust emitting source
today z 4.69
(Omont et al. 1996)
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
6High redshift CO emission detections (as of July
2001)
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
7NGC4550 a galaxy with two counterrotating stellar
populations Virgo cluster (17 Mpc or z 0.0037)
HST images of the central region shows a dust
component. Weak FIR emission detected by IRAS
CO(1-0) emission profile observed with the IRAM
30m telescope (Wiklind Henkel 2001). No
information about distribution (beam size 23).
from Wiklind Henkel 2001
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
8NGC 4550
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
9- The sensitivity and angular resolution should
equal or surpass - that of present day optical and infrared
telescopes. - The scientific goals involve studying the
smallest structure and - the largest distances.
- In nearby galaxies we should be able to observe
the structure - of individual molecular clouds (1 pc at 10 Mpc).
- In distant galaxies we should be able to observe
individual - molecular clouds (100 pc at 1000 Mpc).
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
10- Array with 64 antennas (possibly more)
- Total collecting area 7238 m2 (today 150 890
m2) - Dish diameter 12 m with a surface accuracy 20 mm
- Longest baseline 12 km
- Frequency coverage 30 920 GHz (10 0.3 mm)
- not continuous 10 bands, 4 implemented at
start - Angular resolution 0.2 (lmm/baselinekm)
- shortest wavelength (0.35mm) at the longest
baseline (12 km) 6 mas - intermediate wavelength (0.8mm) and baseline (3
km) 50 mas - Instantaneous bandwidth 16 GHz
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
1136th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
1236th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
13The main science drive for ALMA is the formation
of stars and galaxies
- Except for non-thermal continuum emission (from
AGNs, GRBs, ) - (almost) all the photons received by ALMA
will originate from elements - heavier than hydrogen and helium (exceptions
radio recombination lines - and LiH).
- Since the heavy elements are produced entirely
in stars and introduced - into the interstellar medium via stellar mass
loss (winds, SNe, ), - mm/submm observations probe stellar products.
- Except for non-thermal continuum emission (from
AGNs, GRBs, ) - all the photons received by ALMA will
correspond to temperatures - lt stellar surfaces (the cold universe).
- The heating agent, though, will be stellar UV
photons, Cosmic Rays - and hard photons from AGNs. The mm/submm
emission thus probes - the star formation activity (and/or the AGN
activity).
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
14HST optical image CO contours
HST optical image
(CO Wilson et al. 2000) (HST Whitmore et al.
1999)
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
15SEST single dish CO(1-0) images of M83
(Andersson et al. 2001)
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
16SEST images of M83 if it was at distances z0.004
and z0.04
This resolution will be achieved for M83 at z lt
0.6 and z gt 2.8 with ALMA!
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
17- Merger of small galactic structures at z 0.4
- There is an excess of blue dwarf galaxies at z
0.5 (Phillips et al. 1997 ) - There is an increase in the merger rate at z
0.5 (Infante et al. 1996 ) - a build-up of large galaxies is taking place at
intermediate redshift
- Intermediate redshifts of great interest in
order to understand how present - day galaxies are formed, how they evolve and
how they are related to objects - observed at high redshifts.
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
18Important issues for the high redshift universe
(for ALMA)
- The epoch of the first metal formation (
galaxy formation?) - At which redshift does ALMA stop detecting
objects? - The star formation density as a function of
cosmic time - Is there a hidden population of dusty galaxies
at high-z? - The chemical evolution of the star forming gas
- Has star formation been the same at all cosmic
times? - The mass function of high redshift galaxies
- Molecular gas and dust measure mass better than
optical light - The heating source of submm sources
- Star formation (enormous rates) or AGN?
- Hierarchical vs. monolithic galaxy formation
scenarios - How many of the Es are formed through mergers?
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
19Important issues for the high redshift universe
(for ALMA)
- Continued from previous viewgraph
-
- Redshift distribution of submm detected sources
- Important for all issues
- The temperature of the CMB radiation as a
function of redshift - Test of quintessence models
- Galaxy correlation function as a function of
redshift - Is there a merger epoch?
- Gravitational lensing
- Statistics, weak lensing and differential time
delays - Large scale structure and cosmological
parameters - S-Z effect in clusters and CMB fluctuations on
small scales
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
20How will the issues be addressed with ALMA?
- Dust continuum emission
- The epoch of metal production (stellar products)
- Star formation density vs. redshift
- Heating of dust and gas (star formation/AGN)
- Galaxy correlation function (number counts)
- Gravitational lensing
- Line emission (molecular lines, atomic fine
structure lines) - The epoch of metal formation (stellar products)
- Mass function of galaxies (measure rotation
curves) - Heating of dust and gas (star formation/AGN)
- Molecular absorption lines
- Chemical evolution vs. redshift
- Temperature of the CMBR vs. redshift
- S-Z effect
- H0 and cosmological parameters (CMB fluctuations)
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
21Relation between look-back time and redshift
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
22The star formation rate density as a function of
Look-back time
redshift
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
23Spectral energy distribution (SED) for an
ultraluminous IR galaxy
Dust emission has a negative K-correction at l
below the peak (approx 100mm)
ALMA frequency range
Data points from Arp220
figure from Barger et al. 2000
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
24The observed flux from dust characterized by a
temperature Td and a solid angle Ws
Where
The optical depth depends on grain density and
properties
At the Rayleigh-Jeans part of the blackbody curve
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
25Observed flux for dust emission from a source with
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
26- MAMBO survey of the cluster A2125 (Carilli et
al. 2001) at 250 GHz (1200 mm)
- Detected sources not associated with cluster
galaxies. - Associated with mJy radio sources (VLA)
- Dusty star forming galaxies at median redshift
2.5
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
27- Combined number counts from SCUBA and MAMBO
blind surveys
- The counts correspond to 850mm (350 GHz).
- Contains data from gravitationally lensed
sources. - Best fit with a Schechter luminosity function
with an exponential cut-off at 10 mJy. - (approximately corresponding to LFIR 1013
Lo)
(from Carilli et al. 2001)
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
28- Field 9 square arcmin, Detection limit 150mJy
at 5s, Resolution 0.1. - Number of sources 212.
- Estimated observing time is 100 hours (total)
- Based on an evolving IRAS 60mm luminosity
function
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
29- Fitting simulated number counts to observed
number counts - IRAS luminosity function
- Pure luminosity evolution
- Source cut-off at z gt 7
flux distribution
Redshift distribution
Luminosity distribution
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
30mm continuum radio continuum of the strongest
SCUBA source in the HDF-N
SCUBA image of the HDF-N
Hughes et al. 1998
Downes et al. 2000
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
31Optically identified submm detected sources (only
three so far) Two of them have large molecular
gas masses (seen through CO emission)
Dust continuum
CO(3-2) emission
z 2.81
AGN Type II
(Frayer Scoville 1999)
z 2.56
Starburst
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
32VLT image of the cluster CL2244-02 at z 0.33
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
33Observability of CO emission lines at high
redshift
Observed antenna temperature is the excess
brightness temperature above the local
temperature of the CMBR
In LTE Tx Tk
DTb decreases with redshift for fixed Tx.
The flux is then
Dust has a larger negative K-correction than CO
lines
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
34Warm and dense
Cool and less dense
Distribution of J-levels of CO for two different
gas components at different redshifts (from
Combes et al. 1999).
Distribution peaks for CO(4-3) and CO(5-4)
transitions, with restfrequencies 461 and 576
GHz, respectively
Observable with ALMA for z lt 6
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
35Expected flux for CO and dust emission (from
Combes et al. 1999)
CO emission
Dust emission
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
36Distribution of J-levels of CO and observed flux
at different redshifts (from Silk Spaans 1997).
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
37- Silk Spaans CO emission observable at any
redshift at wavelenghts - longer than 1 mm.
- Combes et al CO emission increasingly
difficult to observe as z - increases (although still observable with an
instrument like ALMA)
Different results because different assumptions
of the gas distribution Silk Spaans assume
a small mean optical depth distributing
Orion-like star forming regions over galactic
scales Combes et al. assume a high mean
optical depth molecular gas very centrally
distributed in a manner similar to ULIRGs
Both groups assume fairly large galaxies, with
1010-1011 Mo of molecular gas, and a high
metallicity
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
38- Metallicity effects on the observability of CO
(and other) molecules at high-z
From observations of nearby dwarf and low surface
brightness galaxies it is known that CO and dust
are underabundant (per blue luminosity, or galaxy
mass) compared to normal spiral galaxies. This is
likely to be an effect of low metallicity (low
abundance of C, O and Si)
When the dust abundance is depleted by a factor 20
- H2 is depleted by 10 (self-shielding)
- CO is depleted by 95
(Maloney Black 1988)
The conversion factor X (molecules of H2 per K
km/s) depends nonlinearly on the metallicity Z.
Possibly as Z-2.2 (Arnault et al. 1988). This has
been confirmed, at least for metallicities 1/10
solar.
CO emission becomes increasingly difficult to
observe as the metallicity decreases
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
39Abundances from Damped Lya systems (Pettini et
al. 1999)
QSOs?
Submm?
(figure from Pettini 2000)
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
40Serendipitously discovered BAL QSO (Irwin et al.
1998) with a R magnitude of 15.2 at high redshift.
(Irwin et al. 1998)
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
41- PdB results for APM082795255
(Downes et al. 1999)
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
42- Low CO rotational levels in APM082795255
- Papadopoulos et al. (2001) find CO(1-0) and
CO(2-1) emission (with the VLA) - Extended emission (different from the high
J-levels found by Downes et al. (1999)) - Additional emission regions, not associated with
APM082795255
from Papadopolous et al. 2001
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
43- The Cloverleaf (H1413117)
- Gravitationally lensed QSO
- Several different molecular transitions detected
- Line ratios model dependent (differential
magnification?)
Barvainis et al. 1997
Kneib et al. 1997
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
44- MS1512-cB58 z2.73, gravitationally lensed by
foreground cluster. - Magnification 30.
- Optical and NIR spectroscopy (Teplitz et al.
2001 Pettini et al. 2000 de Mello et al. 2000) - Show a star forming galaxy (mass 1.2 1010 Mo)
with a SFR of 650 Mo/yr and a metallicity - 1/3 of solar. Is cB58 a typical high-z galaxy?
from de Mello et al. 2000
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
45- One of the reddest LBG
- The restframe UV properties overestimates the
predicted FIR flux - LBGs can account for a small fraction of the FIR
background (lt20) - Possible caveat differential magnification of
UV and FIR emission - (compare with the Antennae)
250 GHz (Baker et al. 2001)
350 GHz (van der Werf et al. 2001)
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
46- Atomic fine structure lines
- CII (158mm), NII (122, 205mm), OI (146mm), CI
(371, 610mm) - Important coolants for the ISM
- CII emission weak for FIR luminous objects but
(relatively) luminous in L galaxies - Require previous stellar generations
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
47- Molecular absorption lines
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
48Molecular absorption, complimentary to emission
Molecular emission and absorption lines probe
different types of molecular gas
Emission lines
Absorption lines
- Emission is sensitive to warm (and dense)
molecular gas - Absorption is sensitive to cold (diffuse)
molecular gas
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
49HST image of the central region of Centaurus A
(Schreier et al. 1998)
HCO(1-0) absorption towards Centaurus A
(Wiklind Combes 1998)
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
5036th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
51Various molecular transitions in absorption at
intermediate redshifts
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
5236th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
5336th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
54- Measuring the temperature of the Microwave
Background Radiation (CMBR)
Millimeter regime
Optical regime
Rotational transitions
Hyperfine structure transitions
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
55- Measuring the temperature of the Microwave
Background Radiation (CMBR)
Redshift
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
56- Strong lensing
- Dust continuum better than optical light for
finding lensed systems - Sufficient angular resolution
- Sensitivity independent on redshift (basically)
- Statistics of lenses important for cosmological
parameters - Allow observations of low-luminosity galactic
structure at early epochs - Weak lensing
- Good for measuring cluster potentials
- Samples background galaxies to very high
redshifts (indiscriminately) - Good angular resolution
- Well-behaved PSF
- Dust distribution rounder than optical emission?
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
57- Example of weak lensing observation with ALMA
- Same field as previously (9 sq. arcmin, 0.15 mJy
_at_ 5s) - Rich cluster at z 0.3
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
58- Present submm receiver systems
- Close to confusion limit due to low resolution
- Sensitivity is 1 mJy, which at z 2
corresponds to gt1012 Lo - Present bolometers can map regions of 9 sq.
arcmin to this depth in 100 hours - Need for high sensitivity and high angular
resolution - ALMA
- Can reach a similar depth with higher angular
resolution in lt 30 minutes - A 2 hour integration at 350 GHz will give a 5s
noise limit of 0.09 mJy - This corresponds to 1011 Lo _at_ z 2
- A field of 360 sq. arcmin at 0.2 Jy would yield
7200 galaxies (done in 2-3 weeks) - The speed of the mapping is essential
(mosaicing, On-The-Fly) -
- Line surveys
- Blind line surveys possible, but depends on the
frequency coverage - Best bands are 70 200 GHz
- With three tunings the entire 3mm window can be
covered - This is complete for all redshifts except z
0.65 1.0 - Detection rate depends on excitation of
molecular gas in high-z galaxies
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA
59- Frequency coverage of CO and HCO over the 3mm
band (70 116 GHz) - For CO lines there is a gap between z 0.65
1.0, otherwise complete coverage
36th Liège International Astrophysical
Colloquium From Optical to Millimetric
Interferometry Extragalactic
Observations with ALMA