Why do we need a vlst for studying qso absorption lines
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Why do we need a VLST for studying QSO absorption lines? PowerPoint PPT Presentation


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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’ (Ly a , weak metal lines)} 

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

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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….


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