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The Host Galaxies of Extremely Strong DLAs
Pasquier Noterdaeme Institut d'Astrophysique de Paris
Galaxies in absorption - Marseille, Dec. 2-4, 2013
Galaxies in absorption - Marseille, Dec. 2-4, 2013
P. Noterdaeme - The host galaxies of extremely strong DLAs
Outline
High-z galaxies in emission
Host galaxies of QSO absorbers?
DLA galaxies
Extremely strong DLAs - distribution - metals - link with GRB-DLAs? - reddening - host galaxy
Conclusions
Galaxies in absorption - Marseille, Dec. 2-4, 2013
P. Noterdaeme - The host galaxies of extremely strong DLAs
→ Lyman-Break Galaxies (Steidel+96)
→ Lyman-α emitters (LAEs) - Narrow-band filters around Lyα line (e.g. Ouchi+08) - Long-slit spectroscopy (e.g. Rauch+08, Cassata+11) - IFU (e.g. Adams+11)
→ IR/mm (e.g. Daddi+09)
→ Absorption
Stellar continuum: bright, massive galaxies (Shapley+03)
Faint in broad-band imaging: low mass systems on average, little dust (Gawiser+07)
Probes the overall luminosity function (e.g. Cen+12)
High SFR, dust
High-z Galaxies (z>2)
Absorption is great but...
Galaxies in absorption - Marseille, Dec. 2-4, 2013
P. Noterdaeme - The host galaxies of extremely strong DLAs
Pune rabbit
Galaxies in absorption - Marseille, Dec. 2-4, 2013
P. Noterdaeme - The host galaxies of extremely strong DLAs
Host galaxies of absorption systems?
→ Most absorbing galaxies are expected to be intrinsically faint
→ Quasar is bright
→ We don't know where to look (how far is the galaxy from the l.o.s?)
→ Hard to associate galaxy with absorber
Need improved observational strategies/efficient instrumentation
low-z: Absorbers-galaxies (e.g. Bergeron & Boissé 1991, Le Brun+97, Turnshek+01, Rao+03, etc.) Galaxies-absorbers (e.g. Noterdaeme+10, York+12, Straka+13). Lorrie's talk
high-z:
Deep, multi-wavelength, long-slit spectroscopy (VLT/Xshooter): get all at once. (e.g. Fynbo+) Integral field spectroscopy: quite large spatial coverage (Céline's talk).
λ → Link gas and galaxy (e.g. Nicolas).
DLA galaxies
Neutral gas cross-section larger than star-light emitting regions → DLA hosts can be found relatively far from the QSO line of sight
Kashikawa+13
→ Wish to go at small impact parameter to probe ISM that directly feeds star-formation → Select very high N(HI). rare!
21cm local Universe (Zwaan+05) high-z (simulations: Pontzen+08)
Fynbo+10
Christensen+
Bouché+12
Fynbo+11
Krogager+12
Bunker+
Moller+93
Moller+04 Noterdaeme+12a Fynbo+13
Galaxies in absorption - Marseille, Dec. 2-4, 2013
P. Noterdaeme - The host galaxies of extremely strong DLAs Also at z<1: Rao+11
Extremely strong DLAs: f(NHI)
→ small incidence compensated by huge number of QSO lines of sight → ~120 000 QSO spectra in BOSS DR10 (Paris+12,+13) → automatic search for DLAs (Noterdaeme+09,+12, *)
Petitjean+93
Noterdaeme+14
→ Using DR11: ~ 100 DLAs with N(HI) = [½ – 2] x 1022 cm-2
Galaxies in absorption - Marseille, Dec. 2-4, 2013
P. Noterdaeme - The host galaxies of extremely strong DLAs * SDSS DLAs: www.iap.fr/users/noterdae/DLA/DLA.html
Extremely strong DLAs: metals
Stack EWs
Δv
N, b
Galaxies in absorption - Marseille, Dec. 2-4, 2013
P. Noterdaeme - The host galaxies of extremely strong DLAs
Extremely strong DLAs: metals
→ Average metallicity ~ 1/20th solar
→ Depletion ~ SMC / MW-Halo
→ Dv ~ 120 km/s
Molecules? (see also Balashev+13)
Ledoux+06
Galaxies in absorption - Marseille, Dec. 2-4, 2013
P. Noterdaeme - The host galaxies of extremely strong DLAs
Extremely strong DLAs: GRBs
Neutral hydrogen
Metals
Differences explained by: - excitation by source? - orientation? - sample size?
Galaxies in absorption - Marseille, Dec. 2-4, 2013
P. Noterdaeme - The host galaxies of extremely strong DLAs
Extremely strong DLAs: QSO colours
→ Ly-α absorption → continuum: some dust?
Galaxies in absorption - Marseille, Dec. 2-4, 2013
P. Noterdaeme - The host galaxies of extremely strong DLAs
Extremely strong DLAs: dust
→ SMC type in most cases (~ most absorbers, York+06, but molecular-rich, cold gas, Noterdaeme+09b, Srianand+08b, Ledoux+, in prep.) → E(B-V) ~ 0.02-0.03 → AV/NHI ~ 10-23 mag cm-2 (~ overall DLA pop, Vladilo+08) → extinction increases with metal EW (~ Khare+12)
Galaxies in absorption - Marseille, Dec. 2-4, 2013
P. Noterdaeme - The host galaxies of extremely strong DLAs
Extremely strong DLAs: Ly-α emission
→ ~ 0.6 x 1042 erg/s
→ idea: light from DLA-galaxy emitted within the fibre, at wavelength where QSO is absorbed Rahmani+10 → observational advantage of ESDLAs: very wide dark core
Galaxies in absorption - Marseille, Dec. 2-4, 2013
P. Noterdaeme - The host galaxies of extremely strong DLAs
weighted
Extremely strong DLAs: Ly-α emission
Distribution
→ mean value (stack / individual) matches that of LAEs with L>0.1x1042 erg s-1
→ distributions match
→ expect ~1/100 with L>5x1042 erg s-1
Noterdaeme+12a, Kulkarni+12
Galaxies in absorption - Marseille, Dec. 2-4, 2013
P. Noterdaeme - The host galaxies of extremely strong DLAs
Extremely strong DLAs: Ly-α emission
Distribution
→ mean value (stack / individual) matches that of LAEs with L>0.1x1042 erg s-1
→ distributions match
→ expect ~1/100 with L>5x1042 erg s-1
Noterdaeme+12a, Kulkarni+12
BOSS
Galaxies in absorption - Marseille, Dec. 2-4, 2013
P. Noterdaeme - The host galaxies of extremely strong DLAs
Extremely strong DLAs: Ly-α emission
Distribution
→ mean value (stack / individual) matches that of LAEs with L>0.1x1042 erg s-1
→ distributions match
→ expect ~1/100 with L>5x1042 erg s-1
Noterdaeme+12a, Kulkarni+12
BOSS
Galaxies in absorption - Marseille, Dec. 2-4, 2013
P. Noterdaeme - The host galaxies of extremely strong DLAs
MagE
Extremely strong DLAs: Ly-α emission
Distribution
→ mean value (stack / individual) matches that of LAEs with L>0.1x1042 erg s-1
→ distributions match
→ expect ~1/100 with L>5x1042 erg s-1
Noterdaeme+12a, Kulkarni+12
BOSS
Xshooter
Galaxies in absorption - Marseille, Dec. 2-4, 2013
P. Noterdaeme - The host galaxies of extremely strong DLAs
MagE
Extremely strong DLAs: Ly-α emission
Kinematics
Galaxies in absorption - Marseille, Dec. 2-4, 2013
P. Noterdaeme - The host galaxies of extremely strong DLAs
Extremely strong DLAs / LAEs: incidence
Incidence of ESDLAs:
Incidence of L>1041 erg/s LAEs:
→ rgas ~ 2.5 kpc i.e. well with the fibre (1” or 8 kpc)
Galaxies in absorption - Marseille, Dec. 2-4, 2013
P. Noterdaeme - The host galaxies of extremely strong DLAs
ESDLAs (from Lyα):
Extremely strong DLAs: SFR
Star-formation rate
(Kennicutt+98)
Kennicutt-Schmidt law: relates surface density and SFR
fesc from 0.05 global galaxy pop. (Hayes+10) to 0.30 in LAEs (e.g. Blanc+11, Nakajima+12). ESDLA observed with Xshooter: fesc~0.20 (Noterdaeme+12a). → SFR ~ 2-3 Msun yr-1
→ rgal ~ 2.5 kpc
Galaxies in absorption - Marseille, Dec. 2-4, 2013
P. Noterdaeme - The host galaxies of extremely strong DLAs
Extremely strong DLAs: Ly-α escape
Dependence on dust?
Galaxies in absorption - Marseille, Dec. 2-4, 2013
P. Noterdaeme - The host galaxies of extremely strong DLAs
Summary/Conclusions
Recall on DLA history: “threshold (log NHI=20.3) ensures neutrality and found similar to local disks. But 5 times larger cross-section at high-z → Early view of √5 times larger galaxies?”
At log NHI~20.3, we don't know where we are.
Locally: 21-cm maps shows that high NHI (~1022 cm-2) probe small b (<5kpc).
High-z: Simulations do show the same (Altay+13, Rahmati+13, Alireza's talk) Observations: relation b vs NHI (for DLAs: Krogager+12)
ESDLAs: Now possible thanks to SDSS-III
1. Absorption properties similar to that of the overall DLA population, integrated properties more similar to that of GRB-DLAs, with some differences that could be explained by geometry (NHI) and excitation (metals).
2. Ly-α in emission. - May be surprising as Ly-α photons need to scatter out the line centre → importance of clumpiness, geometry, viewing angle (Kulas+12, Noterdaeme+12a, Lausen+13, Zheng & Wallace+13). - Luminosity distribution, kinematics and incidence match that of LAEs with L>1041 erg/s from emission- selected surveys. → Similar to the population found by Rauch+08. SFRs ~ 2-3 Msun yr-1
High-metallicity DLAs (Fynbo+): galaxies higher SFRs but larger b. Outskirts of LBGs?
Starting to get a consistent picture of DLAs vs emission-selected galaxy population. Next step: deep, multi-wavelength spectroscopic follow-up!
Thank you!
Galaxies in absorption - Marseille, Dec. 2-4, 2013
P. Noterdaeme - The host galaxies of extremely strong DLAs
DLA galaxies
Kashikawa+13
21cm local Universe (Zwaan+05) high-z (simulations: Pontzen+08)
Fynbo+10
Christensen+
Bouché+12
Fynbo+11
Krogager+12
Bunker+
Moller+93
Moller+04 Noterdaeme+12a Fynbo+13
Galaxies in absorption - Marseille, Dec. 2-4, 2013
P. Noterdaeme - The host galaxies of extremely strong DLAs