UV Spectroscopy of Star-Forming Galaxies

Alessandra Aloisi(ESA/STScI)

Star-Forming Galaxies in the Local Universe

• SF is ongoing in nearby Sp and Irr

• Starbursts mostly in dwarfs & interacting/ merging galaxies

M31

SMC

NGC 5253

Antennae

Star-Forming Galaxies in the High-z Universe

HDF-N• Merging of galaxies

predicted by hierarchical scenarios

• Population of star-forming and

interacting galaxies observed at z 1

(e.g., LBGs)

HDF-S

MS 1512-cB58

Probing Nearby Star-Forming Galaxies

• Laboratories to test SF, evolution of massive , & ISM

• Easy targets where to infer SF history, chemical & physical evolution

• Low-z templates for the high-z Universe

Tremonti et al. 2001

Dolphin et al. 2003

Sextans A

NGC 5253 & MS 1512-cB58

• SF young , massive, hot rest-frame UV HST optical for z > 2-3 JWST 1-5 for z > 4-5

• Rest-frame UV rich in transitions of abundant ions/atoms

emission & absorption

ISM absorption

UV Spectroscopy

González Delgado et al. 1999

NGC 7714

Absorption (Emission) Lines

• Broad low resolution FWHM > 100 km/s

• Spectral evolution synthesis models SB99 regime age SFR extinction

• Many studies HUT HST FUSE GALEX

Tremonti et al. 2001

NGC 5253: stellar clusters

ISM Absorption Lines

• Narrow high resolution FWHM ~ 5-15 km/s

• Physics, chemistry, & kinematics molecular gas -T=102-3K neutral gas -T=102-3 K ionized gas -T=104 K coronal gas -T=105-6 K

• Pilot studies HST/GHRS & STIS NUV (1200-3200 Å) FUSE FUV (900-1200 Å)

Leitherer et al. 2002

M83: HUT (4 Å/pixel) & FUSE (0.04 Å/pixel)

Molecular Gas (H2)

• FUSE band < 1120 Å rich in H2 absorption lines

• No detection of H2 in SBs & BCDs N(H2) < 1015 cm-2

Vidal-Madjar et al. 2000

I Zw 18

Hoopes et al. 2004 (submitted)

SBMW

H2 in dense clouds - ƒ < 1

H2 in diffuse ISM destroyed ?

Neutral Gas

Aloisi et al. 2003

• Few studies with GHRS

• FUSE suitable for most abundant species – H I, O I, Ar I, Si II, P II, C II, N I, & Fe II

• 3 BCDs studied in detail: I Zw 18, I Zw 36, & Mkn 59

• ~ 25 SBs & BCDs will be analyzed in the future

Thuan et al. 1997

I Zw 18

SBS 0335-052

H I more metal-poor than H II ?

Ionized Gas & Dust

• Need of STIS in addition to FUSE: Ionization C I, C II, C III, C IV Fe II, Fe III Si II, Si III, Si IV Al II, Al III

Depletion Zn & Mn - Fe Fe-peak elements S - Si & O elements • F in star-forming galaxies - < 0

lower fluxes in STIS than in FUSE

only NGC 1705 with Echelle data

GHRS & STIS Spectra of NGC 1705

STIS E140M 0.015 Å/pixel - 4 km/s Vázquez et al. (2004)

GHRS G140L 0.56 Å/pixel - 140 km/s Heckman & Leitherer (1997) Sahu & Blades (1997) Sahu (1998)

Coronal Gas

• FUSE provides access to O VI 1032, 1038 doublet

• O VI absorption in few SBs voutflow = 102-3 km/s

• Only NGC 1705 modeled

Heckman et al. 2001

Outflow of hot gas through holes in

a fragmented superbubble shell

Requirements for the VLST

• Abundances, ionization, depletion, kinematics, & physics of ISM wide UV spectral range 900-3200 Å

• Saturation, multiple components, weaker lines high-resolution R = 20,000-50,000 v = 15-5 km/s

• More SBs + normal SF galaxies & reddened galaxies + fainter QSOs + higher z flux limit F << 10-16 erg/sec cm2 Å @ 1400 Å

• Spatial sampling of ISM long slit , MOS, or integral field spectroscopy

Conclusions

Emerging picture for ISM in nearby Universe will:

1. help in understanding chemical & physical evolution of local SF galaxies

2. complement picture for Ly systems at higher z:

local / low z high z (dusty) SF regions inactive regions ISM in galaxy cores galaxy halos & IGM

3. serve as template for high-z SF galaxies - LBGs