Why do we need a VLST for studying QSO absorption lines?

So that

we can

go deeper…

Brilliant! A Genius!! sublim

e….

The Critics agree….

QSO absorption lines and a VLST

My top-three topics for QAL studies in the UV:

{detailed probing of the `cosmic web’ (Ly, weak metal lines)}

metallicity of nearby galaxies QSO absorption lines from QSOs (briefly)

What about metallicity?

• Measurements from QSO absorption lines show little evolution from z=4 to ~1

• The lack of evolution appears to be largely independent of column density – from Ly-forest clouds to Damped Ly

systems (DLAs)

What about metallicity?

Pettini (2003)

• DLAs in particular don’t approach solar at z=0

5.8 – 1.2 Gyr

13.5-5.8 Gyr

Kinda surprising…. expect `gas’ in the universe to be getting more enriched with time as galaxies evolve

and pollute

Let’s measure metallicities from nearby galaxies…

Advantages of looking at nearby galaxies:

•determine wide range of galaxy properties (21cm, X-ray, etc.)

•select low luminosity galaxies that are hard to see at higher-z

•check for fainter interlopers close to any selected galaxy

•easier to examine the galaxy’s environment (isolated, group, cluster)

QSO absorption lines from nearby galaxies

NGC 4319, v=1405 km s-1

Mrk 205, z=0.071

Time for one example…… to show what can be done and how

far we’ve got

Used HST + STIS to measure abundances towards

HS1543+5921 / SBS1543+593

With:

Ed Jenkins,

Todd Tripp,

Max Pettini

10’

HS 1543+5921z=0.807

DSS image

SBS1543+593

APO 3.5m, R, 15 min

QSO

HII region,z=0.009

(2700 km s-1)

star

Reimers& Hagen 98

HST STIS (clear), 800s

QSO

star

Spectroscopy

F(1200) = 2.6x10-15 pretty hard even with first-order gratings; fortunately CVZ object (15 orbits)

[S/H] = -0.4

Higher than

expected?

Compare Zs with DLA samples

Pettini (2003)

HS1543+5921

PG1543+489

List of other suitable pairs which can be observed at high spectral resolution

with HST:

Name of QSO Name of f/g galaxy

What could we do with a VLST?

•There are plenty of QSO-galaxy pairs in the sky! Just too faint!

•Go deeper, the number of interesting pairs becomes substantial

STIS echelle

What could we do with a VLST?

•There are plenty of QSO-galaxy pairs in the sky! Just too faint!

•Go deeper, the number of interesting pairs becomes substantial

•Already know some QSO intercept large N(H I) from 21cm maps [knowing HI a priori helps choose a target to measure Z]

•Four examples, just to show what we’re missing out on….

•VLA maps from Womble (1993)

•optical images from DSS

Gal: IC1746

cz = 5201 km/s

QSO: 0151+045

sep = 10 kpc

V=14.8?

F(1220)=3e-15

==30 STIS orbits

Nice edge-on galaxy probe outer disk

CaII:

N(H I) ~ 7-13 e19 cm/2

Gal: NGC3184

cz = 592 km/s

QSO: 1015+416

sep = 11 kpc

V=17.7 – 19.1?

F(1220)=?

chance to probe edge of huge HI envelope…

…compare to metallicties from HII regions…

CaII:

N(H I) ~ 4e19 cm/2

Gal: NGC470

cz = 2374 km/s

QSO: Q0117+031

sep = 10 kpc

V=18.2

F(1220)=?

NGC 474

19.9

CaII:

N(H I) ~ 6-10 e20 cm/2

Gal: NGC3079

cz = 1125 km/s

QSO: Q0957+558

sep = 8 kpc

V=17.4

F(1220)=1e-15

2.5 hrs, F658N, WFPC2Great way to study outflows!

CaII: N(H I) ~ 3 e20 cm/2

…or multiple QSOs!

Arp et al 2002

NGC 3628

(cz=843 km/s)

QSOs have ‘O’ mags between 18.7 and 20.7

4 X-ray sources

near M65

…or multiple multiple QSOs!

(narrow metal lines

instead of DLAs)

Summary• There are plenty of QSO-galaxy pairs known:

– though number with 21cm maps and/or CaII/NaI observations is smaller– more behind galaxy disks to appear with GALEX presumably– … and using SDSS photo-z techniques

• Need UV telescope that can:– reach 10 km/s resolution down to 20 mag

• factor of 250 in flux over STIS G140M echelle– large wavelength range to cover many lines

• important for ionization corrections• …. and for studying relative abundunace patterns which can be used

to infer history of metal production – how about…. a LiF coated mirror and do < 1100A as well? i.e.

HST+FUSE

• Payoff: – detailed inventory of galaxy metallicities in the local universe– for individual galaxies:

• ability to compare ISM abundances with values from HII regions• variations of metallicities as a function of radius if multiple

sightlines available• kinematics and ionization structure of gas in the outer regions of

galaxies– probes of the interface between a galaxy and the IGM

QSO absorption lines from QSOs

Suppose instead of probing galaxies, could probe QSOs instead.

• QSOs are ejecting large amounts of metal-enriched gas into the IGM might expect:– metallicity of the gas around a QSO to be high– ionization of the gas to be high– absorption to be complex from outflows mixing with the

IGM

• By observing many QSO-QSO pairs, should be able to track the enrichment of the IGM with radius

• Compare absorption from a f/g QSO with associated absorption (zabs ~ zem) in the QSO’s spectrum– learn more about associated systems, compare structure,

ionization, and metallicity variations over small scales.

Available QSO-QSO pairs

• SDSS provides a large # of QSO pair candidates with the b/g QSO < 20th

• Often require follow-up spectra of one of the pairs from the ground– both from collaborators: Joe Hannawi, Gordon Richards

and Michael Strauss

J0836+4841

z=1.71

z=0.66

4.1”,

19 h-1 kpc

J0836+4841

•zabs = zQSO = 0.66 in SDSS spec

•Likely to be a DLA!

•Probably host galaxy

•Perhaps high metallicity?

J2313+1445

zbg = 1.52

zfg = 0.79

sep = 6.4” or

32 h-1 kpc

3e-16

- outflowing gas from jet

-companion fuelling QSO

- unrelated galaxy in

QSO cluster

A future project

• QSOs appear to cause the same kinds of MgII systems that field galaxies cause

• Will need a VLST to do the kinds of spectroscopy of interest….