Download The Intricate Role of Cold Gas and Dust in Galaxy Evolution at Early

The Intricate Role of Cold Gas and Dust in
Galaxy Evolution at Early Cosmic Epochs
ALMA Press Release Nov 11, 2014
Dominik A. Riechers
Cornell University
IAU XXIX General Assembly, S319
August 12, 2015!
Credit: B. Saxton (NRAO/AUI/NSF)
Riechers et al. 2013, Nature, 496, 329
Riechers et al. 2014, ApJ, 796, 84
Capak et al. 2015, Nature, 522, 455
with: !
P. Capak (Caltech), C. Carilli (NRAO), N. Scoville (Caltech), V. Smolcic (Zagreb), E. Schinnerer (MPIA),
M.Yun (UMass), P. Cox (ALMA), F. Bertoldi, A. Karim (Bonn), L.Yan (IPAC), the COSMOS & HerMES teams!
!
http://www.almaobservatory.org/en/press-room/press-releases/772-alma-finds-best-evidence-yet-for-galactic-merger-in-distant-protocluster
http://www.almaobservatory.org/en/press-room/press-releases/860-alma-detects-first-traces-of-carbon-smog-permeating-interstellar-atmospheres-of-early-galaxies
history of the universe!
big bang!
recombination!
Volume density of star formation in galaxies as f(cosmic time)!
z~15-1000!
0.0003-0.3 Gyr!
“Epoch of
galaxy assembly”!
reionization!
?!
z~6-15!
0.3-1 Gyr!
Present day!
First galaxies!
Bouwens et al. 2011!
dark ages !
z~1000!
0.0003 Gyr!
cosmic star formation!
Stellar Light
Stars+Dust
Star Formation in Galaxies at High Redshift:!
quasar/galaxy!
build-up!
z<~6!
>1 Gyr!
!
sites of star formation enshrouded by dust, absorbing a fraction of
the stellar light (which is re-radiated in the rest-frame far-infrared)
at z<3, most star formation is obscured by dust…
today s!
universe!
z~0!
13.8 Gyr!
…at z>3, no direct measurements are available (below bright end)
reason: limited sensitivity/source confusion of submm surveys
!  how can we measure dust-obscured part of the cosmic SF history?!
M100
Herschel/SPIRE! ALMA!
Flux density
Credits: X-ray: NASA/CXC/SAO/D.Patnaude et al, Optical: ESO/VLT, Infrared: NASA/JPL/Caltech
Spectral Energy Distribution
!
250 !
350 !
500 µm!
wavelength
-  idea: z>4 galaxy dust spectral energy distributions peak beyond 500 µm!
! can use (sub)mm colors to determine reasonable photometric redshifts!
! “red” sources are strong candidates for starbursts at the earliest epochs
Systematic approach, but…how well does it work?!
!
!
Riechers et al. 2013b!
Follow up !
with all we have:!
!
Galaxy confirmed!
… at z=6.3369 !!!
Lines are associated with gas
in star-forming regions
Observed 880 million years after the Big Bang
Big Bang
HFLS3
!
(current age: 13.8 billion yrs)
today
Detect!
7 CO lines!
7 H2O lines!
H2O+!
NH3 (absorption)!
OH!
OH+ (absorption)!
[CI]!
[CII]!
Hints of others…!
!  Highly enriched!
!
Gray line is best
existing spectrum
of nearby starburst!
Riechers et al. 2013b, Nature!
Almost as many stars as the Milky Way!
Similar total mass, already at z=6.34!
40x more gas!
2000x more star formation!
…and ~20x more star formation !
than extreme nearby starburst!
!
…consistent with a so-called!
! “maximum starburst” galaxy!
Also: a compact (~3.5kpc), high velocity dispersion gas reservoir!
!  High star formation rate likely driven by a major merger!
!  An extraordinary starburst, even compared to others at high z!
Riechers et al. 2013b!
Use to calibrate submm/radio photo-z’s:
!  “red” sources have <z>=4.7
Extrapolate luminosity function (Bethermin models):
!  Contribution to SFHU may be comparable to UV-selected galaxies!
But: large extrapolation required – need to measure faint end directly…
latest progress on “red” sample: D. Clements’ talk tomorrow!
Dowell et al. 2014!
Molecular Gas!
2x2 arcmin2
COSMOS/AzTEC-3 (z=5.3) !
!  AzTEC-3: Most Distant Massive Starburst Galaxy 2010-13
Mgas = 5.3 x 1010 ("co/0.8) Msun
SFR: ~1100 Msun/yr … or >3 Msun/day
!
!  Most Distant Galaxy Proto-Cluster:!
11 star-forming galaxy companions within r~2 Mpc
Hubble Space
Telescope!
+
Karl G. Jansky Plateau de Bure
Very Large Array! Interferometer!
+
(1.1 billion years after Big Bang)!
(20x Milky Way) !
(Milky Way: ~2 Msun/yr)!
(>10x cosmic average at epoch)
!
Riechers, Capak et al. 2010, ApJ!
Capak, Riechers et al. 2011, Nature!
~6.2mJy cont.!
Dusty starburst!
<0.15mJy/beam cont.!
Triplet of Ly-break galaxies!
rms: 50 microJy/beam!
!  New ALMA 158 µm image of the central region!
!  Image of bright dust and star formation in AzTEC-3 !
!  “star factory” at work in region only 2.5 kpc across!
!  #SFR = 530 Msun/yr/kpc2 => “maximum” starburst!
ALMA
!
!
~62 min/pointing w/ 16-24 antennas
!
Riechers et al. 2014b!
~6.2mJy cont.!
Dusty starburst!
<0.15mJy/beam cont.!
Triplet of Ly-break galaxies!
rms: 50 microJy/beam!
!  New ALMA 158 µm image of the central region!
!  Image of bright dust and star formation in AzTEC-3 !
!  “star factory” at work in region only 2.5 kpc across!
!  #SFR = 530 Msun/yr/kpc2 => “maximum” starburst!
ALMA
!
!
~62 min/pointing w/ 16-24 antennas
!
Riechers et al. 2014b!
atomic!
[CII]
molecular!
!  ALMA image of star-forming gas!
1000 km/s
!  Detect atomic and molecular gas: [CII]158µm & OH163µm!
!  Gas distributed over highly-dispersed region ~4 kpc across!
Mdyn ~ 1011 Msun => fgas ~ 55%
log10(LCII/LFIR) = -3.40!
!  Some tidal structure and possible outflow signatures!
!  Recent interaction, witnessing peak phase of starburst!
Riechers et al. 2014b!
all galaxies!
atomic!
dvFWHM = 93+/-32 km/s!
152+/-29 km/s!
250+/-41 km/s!
!  ALMA image of star-forming gas!
!
!  Gas in a triple of “companions” ~8 kpc apart!
!  Galaxies together form ~50 times less stars than Az-3!
!  [CII]/FIR >0.3%-0.9%: “normal” galaxies at this epoch!
!
!  A new window on galaxy formation: ALMA detects gas in
“typical” star-forming galaxies 12.7 billion years in the past!!
Riechers et al. 2014b!
No CO in deep VLA data:!
LCII/LCO > 4600!
(3!)!
!
!  [CII] much easier…!
PdBI!
No old stellar populations, no dust!
!  “dwarf-like” SED shape!
!  ALMA image of star-forming gas!
!
!  Gas in a triple of “companions” ~8 kpc apart!
!  Galaxies together form ~50 times less stars than Az-3!
!  [CII]/FIR >0.3%-0.9%: “normal” galaxies at this epoch!
!
!  A new window on galaxy formation: ALMA detects gas in
“typical” star-forming galaxies 12.7 billion years in the past!!
Riechers et al. 2014b, 2015!
General property or environmental bias?!
!
Build on AzTEC-3/LBG-1 result:!
!
ALMA cycle-1 study of representative
sample of 10 z=5-6 Ly-break galaxies!
(COSMOS; Keck/DEIMOS sample)!
example Keck spectra!
!
SFRs: 18-170 Msun/yr (~L*UV; LIR~1010.3-1012 Lsun)!
!
Z~5-6 UV Luminosity Function
Target [CII] 158 µm line & dust continuum!
10
(typ. 2-3x deeper than in cycle-0)!
This sample!
-2
-1
[158 micron fluxes: 129-1261 µJy]!
non-detections detected in stack!
[stacked flux: 35+/-13 µJy]!
Capak, Carilli, Jones, Casey, DR et al. 2015!
-3
tentative??!
N Mpc Mag
Flux density [mJy]
!
[CII]: detect 11/10 galaxies!!
normal, 170-380 km/s FWHM lines!
!
Dust: detect 4/10 galaxies (mostly weak)!
10
10
-4
10
10
-3
-5
-6
-7
10
This Proposal
-8
10 -24
-23
-22
-21
MUV(1600)
Velocity offset [km/s]
-20
-19
log10(LIR/L1600A)!
log10 L[CII]/LIR!
log10 LIR [Lsun]!
[CII]/FIR ratio above“typical” local galaxies!
" low dust content, low metallicity?!
But: large scatter!
!
Typically: LCII ~ 0.3% Lbol!
Capak et al. 2015, Nature!
UV slope, $%
~12x less dust than z<3 LBGs!
!  Apparently strong evolution of IRX-$%
!  2-4x lower attenuation of SFRUV!
Consistent w/ local dwarf (SMC) like dust!
!
But: significant scatter!
log10 SFR [Msun/yr]!
L[CII] [Lsun]!
log10 SFR [Msun/yr]!
Rough [CII]-SFR relation (~1 dex scatter)!
holds, but UV SFRs would be ~2-10x too high
with standard (lower-z) dust corrections!
Capak et al. 2015, Nature!
log10 M* [Msun]!
The majority of sources is consistent with
“main sequence” galaxies at their redshift!
log10 SFRD [Msun/yr Mpc-3 ]!
redshift!
z~5-6 LBGs appear to be significantly (~12x) less dusty than z<3 LBGs!
!
! possibly steeper decline of dust-obscured fraction of SFHU than
previously thought: ~30%-40% downward correction at z~6!
Capak et al. 2015!
!
#  dust-obscured
star formation::
- need to quantify its contribution to fully constrain cosmic history
- now can detect massive, dust-obscured starbursts out to z>6
- starting to access rich molecular and fine structure line diagnostics
- commonly “maximum starbursts”, scaled-up nearby ULIRGs
#  “typical”
galaxies at z=5-6:
- ALMA suitable to detect star-forming gas in z>5 Ly-break galaxies
- [CII] 158 !m: good indicator of redshifts and galaxy dynamics at z>5
- [CII] easier to detect than dust in early galaxies, as metallicity drops
- now directly observed drop in IRX-$ from z=3 to z=6 with ALMA: !
=> plan conservatively!!