Probing the Universe with QSO Absorption Lines

David TurnshekUniversity of Pittsburgh

Outline:Outline: QSO Absorption Line OverviewQSO Absorption Line Overview Investigating the Neutral Gas ComponentInvestigating the Neutral Gas Component Future Work with SDSS DataFuture Work with SDSS Data

Collaborators:Collaborators: Sandhya RaoSandhya Rao Daniel NestorDaniel Nestor Brice MenardBrice Menard Eric MonierEric Monier Michele Belfort-MihalyiMichele Belfort-Mihalyi Andrew HopkinsAndrew Hopkins Lorenzo RimoldiniLorenzo Rimoldini Ravi ShethRavi Sheth Daniel Vanden BerkDaniel Vanden Berk Stefano ZibettiStefano Zibetti Anna Quider Anna Quider + new SDSS collaborators …+ new SDSS collaborators …

Quasar Absorption Lines: Probing the Gas in the Universe

Courtesy John Webb

Quasar spectroscopy offers the opportunity to study foreground gas.

MotivationMotivation galaxy formation galaxy formation conversion of gas into stars conversion of gas into stars

probe to large redshift (look back time) without probe to large redshift (look back time) without luminosity biasluminosity bias

use QSO absorption lines to study:use QSO absorption lines to study: dark matterdark matter extragalactic UV ionizing backgroundextragalactic UV ionizing background structure formationstructure formation physical properties of gas/dust physical properties of gas/dust

e.g., gas-phase metallicity, ionization, density, temperature, e.g., gas-phase metallicity, ionization, density, temperature, distribution and extent, distribution and extent, gasgas

QSO Absorption-Line JargonQSO Absorption-Line Jargon

Intrinsic QSO Absorbers (e.g. BALs) Intrinsic QSO Absorbers (e.g. BALs) tomorrow tomorrow

LyLy ( (forest:forest: weak systems trace the dark matterweak systems trace the dark matter z>1.65 (optical spectroscopy), z>2.2 (SDSS)z>1.65 (optical spectroscopy), z>2.2 (SDSS)

Metal-Line Systems:Metal-Line Systems: OIV – samples high ionizationsOIV – samples high ionizations CIV – samples moderate ionizationsCIV – samples moderate ionizations MgII - samples a large range in HI column densityMgII - samples a large range in HI column density

LyLy forest forest Lyman LimitLyman Limit Damped LyDamped Ly(DLA)(DLA)

DLAs (bulk of neutral gas component!)DLAs (bulk of neutral gas component!)

Some QSO Absorption Line Some QSO Absorption Line StudiesStudies

LyLy forest: forest: ground-based +HST (Weymann et al)ground-based +HST (Weymann et al) Keck/VLT Hi-Res Keck/VLT Hi-Res 1.5<z<4, 90% of baryons in 1.5<z<4, 90% of baryons in

forest forest SDSS (Bernardi et al) SDSS (Bernardi et al) near z=3, signature of HeII near z=3, signature of HeII

reionization (temp, opt depth)reionization (temp, opt depth) SDSS (McDonald, Seljak et al) SDSS (McDonald, Seljak et al) clustering, power clustering, power

spectrum, cosmological parameters, neutrino massspectrum, cosmological parameters, neutrino mass

Metal-Line Systems:Metal-Line Systems: ground-based CIV + MgII Surveys (Sargent et al; ground-based CIV + MgII Surveys (Sargent et al;

Churchill et al)Churchill et al) HST OVI Surveys – warm-hot IGM (Tripp et al)HST OVI Surveys – warm-hot IGM (Tripp et al)

Weymann et al. (1998): Weymann et al. (1998):

Steidel, Sargent, Boksenberg (1988):Steidel, Sargent, Boksenberg (1988):

courtesy Chris Churchill:courtesy Chris Churchill:

QSO Absorption-Line JargonQSO Absorption-Line Jargon

Intrinsic QSO Absorbers (e.g. BALs) Intrinsic QSO Absorbers (e.g. BALs) tomorrow tomorrow

LyLy ( (forest:forest: weak systems trace the dark matterweak systems trace the dark matter z>1.65 (optical spectroscopy), z>2.2 (SDSS)z>1.65 (optical spectroscopy), z>2.2 (SDSS)

Metal-Line Systems:Metal-Line Systems: OVI – samples high ionizationsOVI – samples high ionizations CIV – samples moderate ionizationsCIV – samples moderate ionizations MgII - samples a large range in HI column densityMgII - samples a large range in HI column density

LyLy forest forest Lyman LimitLyman Limit Damped LyDamped Ly(DLA)(DLA)

DLAs (bulk of neutral gas component!)DLAs (bulk of neutral gas component!)

Damped Lyman Alpha lines: NHI > 2 x 1020 atoms cm-2

DLA systems are very rare.

Yet, they contain about 95% of the neutral gas mass in the universe.

They are important because

galaxy formation and evolutioninvolves the collapse of neutral gasthat eventually forms stars.

by tracking DLA systems back in time (redshift), we can study galaxy formation and evolution.Kim et al. 2002

f is the frequency distribution of HI column densities.

The Lyman-Alpha Absorption Line of Neutral Hydrogen

HI Ly

The shape of an absorption linedepends on the column density ofthe gas, N, and the thermal velocity of the gas, b.

b = 2 vrms

1 cm2

N = number of atoms per cm2

along the line of sight

“Damped Ly”””

The curveof growth

20 Years of Searching for 20 Years of Searching for DLAsDLAs

interested in selecting galaxies by gas cross-interested in selecting galaxies by gas cross-section (e.g., sightline through MWG section (e.g., sightline through MWG DLA) DLA)

Wolfe, Turnshek, Smith, Cohen (1986) Wolfe, Turnshek, Smith, Cohen (1986) probed redshifts z = 1.7 probed redshifts z = 1.7 3.3 from the 3.3 from the groundground found excess in gas cross-sections times number found excess in gas cross-sections times number

of absorbers (compared to expectations at z=0)of absorbers (compared to expectations at z=0) found found HIHI(hi-z) approximately equals (hi-z) approximately equals **(z=0) (z=0) redshifts too high to search for galaxy light in the redshifts too high to search for galaxy light in the

optical (cosmological dimming) optical (cosmological dimming)

Courtesy John Webb

H I 21 cm Maps of Some Nearby Galaxies:

VLA and WSRT maps courtesy John Hibbard, NRAO

H I 21 cm Maps of Some Nearby Galaxies:

VLA and WSRT maps courtesy John Hibbard, NRAO

H I 21 cm Maps of Some Nearby Galaxies:

VLA and WSRT maps courtesy John Hibbard, NRAO

Optical Images of Stars in M51:Courtesy NOAO

Deep exposure Short exposure

How to Probe to Low-z?How to Probe to Low-z?

Problem: need scarce HST UV Problem: need scarce HST UV spectroscopy time to search at z<1.65 spectroscopy time to search at z<1.65 z<1.65 covers 70% of the age of the z<1.65 covers 70% of the age of the

Universe!Universe!

Problem: DLAs are rare (0.2 per unit z Problem: DLAs are rare (0.2 per unit z at hi-z, and more rare at low-z)at hi-z, and more rare at low-z) HST QSO AL Key Project found only one HST QSO AL Key Project found only one

DLA during its 4 Cycles of HST observation.DLA during its 4 Cycles of HST observation.

How to Probe to Low-z?How to Probe to Low-z?

Solution: use low-z (z>0.13) MgIISolution: use low-z (z>0.13) MgII AL systems as tracers for DLAs and AL systems as tracers for DLAs and measure Nmeasure NHI HI with HSTwith HST Rao, Turnshek, Rao, Turnshek, Briggs (1995)Briggs (1995) Rao, Turnshek (2000)Rao, Turnshek (2000) Rao, Turnshek, Nestor (2004)Rao, Turnshek, Nestor (2004)

SDSS Spectrum of MgII SDSS Spectrum of MgII AbsorptionAbsorption

z=0.741 MgII absorption system (REW2796 = 2.95Angstroms)z=0.741 MgII absorption system (REW2796 = 2.95Angstroms)

Right: Strong MgII doublet and weakerMgI line.

Left: Two Strong FeII lines and threeweaker MnII lines.

Optical MgII AL SurveysOptical MgII AL Surveys

z = 0.37z = 0.372.27: SDSS spectroscopy of 3700 2.27: SDSS spectroscopy of 3700 QSO sightlines (Nestor, Turnshek, Rao 2004) QSO sightlines (Nestor, Turnshek, Rao 2004) >1300 MgII systems>1300 MgII systems REW > 0.3 AngstromREW > 0.3 Angstrom

z = 0.14z = 0.140.96: MMT spectroscopy of 400 0.96: MMT spectroscopy of 400 QSO sightlines (Nestor, Turnshek, Rao 2005)QSO sightlines (Nestor, Turnshek, Rao 2005) 141 MgII systems141 MgII systems REW > 0.1 AngstromREW > 0.1 Angstrom

Interpretation of Absorption Interpretation of Absorption

Rest Equivalent Width Rest Equivalent Width (REW)(REW)

Due to “curve-of-Due to “curve-of-growth” saturation growth” saturation effects, MgII REWs effects, MgII REWs mostly measure mostly measure kinematic spread.kinematic spread.

REW=1 Angstrom REW=1 Angstrom black absorption black absorption > 107 km/s.> 107 km/s.

How to Probe to Low-z?How to Probe to Low-z?

Solution: use low-z (z>0.13) MgIISolution: use low-z (z>0.13) MgII AL systems as tracers for DLAs and AL systems as tracers for DLAs and measure Nmeasure NHI HI with HST with HST Rao, Turnshek, Rao, Turnshek, Briggs (1995)Briggs (1995) Rao, Turnshek (2000)Rao, Turnshek (2000) Rao, Turnshek, Nestor (2004)Rao, Turnshek, Nestor (2004)

Infer DLA statistics from MgII statisticsInfer DLA statistics from MgII statistics

SDSS Redshift-REW Sightline SDSS Redshift-REW Sightline CoverageCoverage

Small REWs Small REWs require high require high S/N for S/N for detectiondetection

Large REWs Large REWs can be can be detected in detected in most most spectraspectra

MgII REW DistMgII REW DistNN: 0.1: 0.15 5 AngstromsAngstroms

Left: Left: SDSS SDSS and MMT and MMT SurveysSurveys

Right: Right: SDSS SDSS Survey Survey alonealone

MgII REW DistMgII REW DistNN: 0.1: 0.11.5 Angstroms1.5 Angstroms

Shows Shows details of details of smaller smaller REWsREWs

Evidence Evidence for two for two PopulationsPopulations??

Evolution of MgII REWs: Evolution of MgII REWs: z=0.4z=0.42.22.2

Dashed: Dashed: no-no-evolution evolution curvescurves

Stronger Stronger systems systems may evolve may evolve away faster away faster

MgII Effective Absorbing Cross-MgII Effective Absorbing Cross-Sections Sections

The incidence, The incidence, dn/dz, depends dn/dz, depends on the product on the product of galaxy cross-of galaxy cross-section times section times comoving comoving galaxy number galaxy number densitydensity

Right: constant Right: constant comoving comoving number densitynumber density

How to Probe to Low-z?How to Probe to Low-z?[Aim: study the neutral gas [Aim: study the neutral gas

component]component]

Solution: use low-z (z>0.13) MgIISolution: use low-z (z>0.13) MgII AL systems as tracers for DLAs and AL systems as tracers for DLAs and measure Nmeasure NHI HI with HST with HST Rao, Turnshek, Rao, Turnshek, Briggs (1995)Briggs (1995) Rao, Turnshek (2000)Rao, Turnshek (2000) Rao, Turnshek, Nestor (2004)Rao, Turnshek, Nestor (2004)

Infer DLA statistics from MgII statisticsInfer DLA statistics from MgII statistics

HST DLA Surveys in Cycles 6, 9, 11HST DLA Surveys in Cycles 6, 9, 11 198 MgII systems studied 198 MgII systems studied 41 DLAs 41 DLAs

identified identified

Some Representative HST DLA Some Representative HST DLA DataData

HST DLA Data: Detection of Double HST DLA Data: Detection of Double DLADLA

Turnshek et al. 2004 zabs=0.945, 1.031N(HI)=1.45E21, 2.60E21 atoms cm-2[Zn/H]=26.5%, 4.7% solar

MgII-FeII-DLA SelectionMgII-FeII-DLA Selection

Filled circles DLAs with NHI > 2 x 1020 atoms cm-2

Left: MgII REW versus FeII REW Right: NHI versus MgII REW

Evolution of Incidence of Evolution of Incidence of DLAsDLAs

solid curve: solid curve: no-evolutionno-evolution

incidence is incidence is product of product of absorber absorber cross-section cross-section times times absorber absorber number number densitydensity

Evolution of HI Evolution of HI Cosmological Mass Cosmological Mass Density from DLAsDensity from DLAs

HI gas mass HI gas mass approximatelapproximately constant y constant from from z=0.5z=0.54.5, 4.5, but is 3x but is 3x lower at z=0.lower at z=0.

Identification of MgII Absorbing Identification of MgII Absorbing GalaxiesGalaxies

Hubble SpaceTelescope imageof a field withseveral quasar absorption linesystem galaxiesidentified. A galaxy at the DLA redshift (z=0.656) is not visible.

Courtesy Chuck Steidel

Quasar 3C336Sightline

Identification of DLA Absorbing Identification of DLA Absorbing GalaxiesGalaxies

Infrared K-band image of the Q0738+313 sightline with DLAs at z = 0.091 and z = 0.221. IDs put the galaxies at 0.08 and 0.1L*, respectively.

Turnshek et al. 2001

Identification of DLA Absorbing Identification of DLA Absorbing GalaxiesGalaxies

Infrared K-band image of the SDSS QSO 1727+5302 sightline with DLAs at z = 0.945 and z = 1.031. IDs for G1 and G2 are, conservatively, 0.06 and 0.15 L*.

Turnshek et al. 2004

Some Results on DLA Galaxy Some Results on DLA Galaxy IDsIDs

?

Evolution of Neutral Gas Metal Evolution of Neutral Gas Metal AbundanceAbundance

Beginning Beginning to measure to measure abundanceabundances at lower-s at lower-z, seeing z, seeing evidence evidence for for evolution.evolution.

Rao et al. 2004

TheoryTheory Prochaska & Wolfe (1997) proposed that Prochaska & Wolfe (1997) proposed that

leading edge asymmetry in hi-z absorption leading edge asymmetry in hi-z absorption profiles were signatures of thick rotating HI profiles were signatures of thick rotating HI disks.disks.

KeckHIRES

TheoryTheory Haehnelt, Steinmetz, Rauch (1998) found Haehnelt, Steinmetz, Rauch (1998) found

that merging fragments could also account that merging fragments could also account for profiles.for profiles.

TheoryTheory Luminous disks as favored by Prochaska & Luminous disks as favored by Prochaska &

Wolfe (1997) ? Wolfe (1997) ? e.g., Eggen, Lynden-Bell, e.g., Eggen, Lynden-Bell, Sandage (1962) scenario of monolithic disk Sandage (1962) scenario of monolithic disk collapse.collapse.

Merging fragments as favored by Haehnelt, Merging fragments as favored by Haehnelt, Steinmetz, Rauch (1998) ? Steinmetz, Rauch (1998) ? e.g., merging e.g., merging hierarchy of CDM halos (White & Rees hierarchy of CDM halos (White & Rees 1978).1978).

Great variety Great variety seems to rule possibility seems to rule possibility that DLAs are exclusively large disksthat DLAs are exclusively large disks..

TheoryTheory Pei, Fall, Hauser (1999):Pei, Fall, Hauser (1999):

Right: Models of Cosmic SF Left: Corresponding Predictions

bary_galbary_flow

Cosmic Star Formation and Cosmic Star Formation and DLAsDLAs

Hopkins: DLAsHopkins: DLAs filled black circles filled black circles

Progress on MgIIs and DLAs with Progress on MgIIs and DLAs with SDSSSDSS

SDSS continues to offer a wealth of knew SDSS continues to offer a wealth of knew informationinformation

Summer 2004: have recently-generated Summer 2004: have recently-generated catalog of 20,000 MgII Absorbers (about catalog of 20,000 MgII Absorbers (about 40% of eventual total) 40% of eventual total)

Preliminary work in many areas …Preliminary work in many areas …

Current SDSS MgII PlansCurrent SDSS MgII Plans 1. Statistical Properties of MgII Absorbers1. Statistical Properties of MgII Absorbers

must improve statistics at higher REWmust improve statistics at higher REW

Only have analyzed 243 MgII systems with kinematically extreme absorption (REW > 2 Angstroms).

Potentially: ~9000

Current SDSS MgII PlansCurrent SDSS MgII Plans 2. Neutral Gas-Phase Element Abundances + Dust 2. Neutral Gas-Phase Element Abundances + Dust

use HST Nuse HST NHIHI measurements and SDSS composites measurements and SDSS composites

Neutral Gas-Phase Element Abundances + Neutral Gas-Phase Element Abundances + DustDust

NNHIHI ~ constant for saturated MgII REWs! ~ constant for saturated MgII REWs! find increasing metallicity with increasing kinematic find increasing metallicity with increasing kinematic

spreadspread

Unsaturated

ZnII

CrII

Turnshek, Nestor, et al 3700+ composite:

Current SDSS MgII PlansCurrent SDSS MgII Plans 3. Gravitational Amplification of Bkgd QSOs3. Gravitational Amplification of Bkgd QSOs

Observed Frame:amplification/reddening (Menard, Nestor, Turnshek 2004)

Top 2 rows,fake data

Bottom row,real data

Current SDSS MgII PlansCurrent SDSS MgII Plans 3. Gravitational Amplification of Bkgd QSOs3. Gravitational Amplification of Bkgd QSOs

Observed Frame:amplification/reddening (Menard, Nestor, Turnshek 2004)

real datacorrected for bias

Current SDSS MgII PlansCurrent SDSS MgII Plans 4. Mean Reddening and Extinction4. Mean Reddening and Extinction

mean reddening in QSO frame (van den Berk)

Current SDSS MgII PlansCurrent SDSS MgII Plans 5. Study of Individual Absorbing Galaxies 5. Study of Individual Absorbing Galaxies

IRTF H-band image of double DLAsightline (z=1) (Belfort-Mihalyi)

z=0.009 DLA dwarf galaxy (Schulte-Ladbeck et al 2004)

Current SDSS MgII PlansCurrent SDSS MgII Plans 6. Mean Integrated Light of Absorbing 6. Mean Integrated Light of Absorbing

GalaxiesGalaxies Can stack images!Can stack images!Right:

Putative MgII gas cross-sections of HST UDF galaxies (Rimoldini).

For SDSS MgII absorbers, a QSO sightline passes through each circle. Stacking images centered on the QSO will yield mean integrated light of absorbing galaxies.

E.g., Composite Light from Halos of Edge-On E.g., Composite Light from Halos of Edge-On

GalaxiesGalaxies Zibetti, White, Brinkmann (2004):

For SDSS MgIISystems: Use images stackedon the position of the QSO to measure the mean integrated light of absorbing galaxies; then compare tonon-absorbed samples of QSOs(Zibetti)

Current SDSS MgII PlansCurrent SDSS MgII Plans 7. Absorber Kinematics and Clustering7. Absorber Kinematics and Clustering

e.g., 2-pt correlation function e.g., 2-pt correlation function null results on initial (small) sample (Rimoldini)null results on initial (small) sample (Rimoldini) but now 20x biggerbut now 20x bigger also, account for velocity substructure (< 500 km/s)also, account for velocity substructure (< 500 km/s)

8. MgII Absorbers and LRGs8. MgII Absorbers and LRGs Bouche, Murphy, Peroux (2004) claim positive Bouche, Murphy, Peroux (2004) claim positive

cross-correlation between MgIIs-LRGs, 0.67 times cross-correlation between MgIIs-LRGs, 0.67 times amplitude of LRG-LRG auto-correlation (212 MgIIs, amplitude of LRG-LRG auto-correlation (212 MgIIs, 20,000 LRGs)20,000 LRGs)

MenardMenard can’t confirm? can’t confirm? but now bigger sample but now bigger sample

Summary: Strong MgII Summary: Strong MgII AbsorbersAbsorbers

Mostly Galaxies Selected by Gas Cross-Mostly Galaxies Selected by Gas Cross-SectionSection

Strong MgII Absorbers Strong MgII Absorbers high-Nhigh-NHIHI DLAs DLAs track evolution of the HI mass in the universetrack evolution of the HI mass in the universe track absorber cross-section times comoving track absorber cross-section times comoving

densitydensity track cosmic neutral-gas phase metallicity + dusttrack cosmic neutral-gas phase metallicity + dust explore lensing/DMexplore lensing/DM expore environment (associated galaxies, expore environment (associated galaxies,

clustering)clustering)