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

Why do we need a VLST for studying QSO absorption lines? So that we can go deeper…

Brilliant! A Genius!! sublime…. 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’ (Lya, 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 Lya-forest clouds to Damped Lya systems (DLAs)

13.5-5.8 Gyr 5.8 – 1.2 Gyr Pettini (2003) What about metallicity? Kinda surprising…. expect `gas’ in the universe to be getting more enriched with time as galaxies evolve and pollute • DLAs in particular don’t approach solar at z=0

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)

NGC 4319, v=1405 km s-1 QSO absorption lines from nearby galaxies 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’ DSS image SBS1543+593 HS 1543+5921 z=0.807

QSO star HII region, z=0.009 (2700 km s-1) APO 3.5m, R, 15 min Reimers & Hagen 98

QSO star HST STIS (clear), 800s

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?

HS1543+5921 PG1543+489 Pettini (2003) Compare Zs with DLA samples

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

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

N(H I) ~ 7-13 e19 cm/2 CaII: 

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…

N(H I) ~ 4e19 cm/2 CaII: 

Gal: NGC470 cz = 2374 km/s QSO: Q0117+031 sep = 10 kpc V=18.2 F(1220)=? NGC 474 19.9

N(H I) ~ 6-10 e20 cm/2 CaII: 

Gal: NGC3079 cz = 1125 km/s QSO: Q0957+558 sep = 8 kpc V=17.4 F(1220)=1e-15

2.5 hrs, F658N, WFPC2 Great way to study outflows!

N(H I) ~ 3 e20 cm/2 CaII: 

…or multiple QSOs! NGC 3628 (cz=843 km/s) QSOs have ‘O’ mags between 18.7 and 20.7 4 X-ray sources near M65 Arp et al 2002

…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

4.1”, 19 h-1 kpc J0836+4841 z=0.66 z=1.71

J0836+4841 • zabs = zQSO = 0.66 in SDSS spec • Likely to be a DLA! • Probably host galaxy • Perhaps high metallicity?

3e-16 J2313+1445 zbg = 1.52 zfg = 0.79 sep = 6.4” or 32 h-1 kpc • - 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….

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