Are There Local Analogs of Lyman Break Galaxies? James D. Lowenthal (Smith College/FCAD) R. Nick Durham (Smith College) Brian Lyons (Amherst College) David C. Koo (UCO/Lick Obs.) Matt A. Bershady (U. Wisconsin) Rafael Guzmán (U. Florida) Jesús Gallego (Universidad Complutense de Madrid) See also: Jason Melbourne (AO) Matt Bershady (internal kinematics) David Koo (z~1) Drew Phillips ([O/H]) Kai Noeske (UDF profiles)

Big question: How do Lyman break galaxies fit into galaxy formation/evolution? Specific motivating questions: What are detailed characteristics of LBGs? Range of LBG masses? Do LBGs reside in much larger, more massive halos, or is it what- you-see-is-what-you-get, i.e., dwarf starburst galaxies? What constraints can we place on LBG host galaxy type? One approach: find local analogs -- easier to study in detail. Then compare to LBGs.

Basic parameters of Lyman break galaxies Sizesr 1/2 ~3 kpc LuminositiesL~L* and up (L<L* hard to study) Colors Very blue (except for Lyman/Lyα breaks) B-V(rest)<0.4 Morphologies Diverse: multiple knots, halos, chains, compact Star Formation Rates 1<SFR<1000 M yr -1 Masses 10 9 < M < M from stellar populations, emission line widths, spatial kinematics Clusteringr 0 ~5 Mpc

Lyman Break Galaxy Examples Lowenthal et al

Possible best local analogs to LBGs: HII galaxies and luminous blue compact galaxies (LBCGs) Sizesr 1/2 <3 kpc Luminosities0.1<L/L*<2 ColorsVery blue: B-V~0.5 MorphologiesDiverse: small disks, irregulars Star Formation Rates 0.5<SFR<25 M yr -1 Masses < M < M from stellar populations, emission line widths Clusteringr 0 ~5 Mpc

LCB Galaxy Examples z<0.05 z~0.75 WIYN R-band (Pisano et al. 2001)HDF-FF I 814 (Phillips et al. 1997) 6 10 kpc

HST/STIS images in rest-UV of HII Galaxies and LCBGs Goal: Compare local starburst and high-redshift LBG samples at same rest-UV wavelength 12 (HII) galaxies from UCM survey (z~0): STIS/FUV images 14 LCBGs from Kitt Peak Galaxy Redshift Survey (z~0.5): STIS/NUV images

STIS FUV images Morphologies: VERY diverse, disturbed, multiple knots z~0 sample 6.5

STIS NUV images Morphologies: more disturbed, multiple knot systems z~0.75 sample 3.75

Rest-UV Asymmetries Measure image asymmetry A following Conselice et al. (2000)

Rest-UV Asymmetries Large range in A; spans median for LBGs LBG median

What would LCBGs and HII galaxies look like at z~3? Simulate z=3 HDF view: –Rebin STIS images –Add noise to match S/N at z=3 Low redshift sample not visible at z=3 (but barely visible in ACS/GOODS/UDF) z~0.75 sample all visible at z=3; morphologies much simpler, more compact; low-SB structure lost.

True z STIS vs. simulated HDF True z Simulated HDF z=3

Rest-UV Asymmetries of simulated z=3 view

Asymmetry affected by z? Asymmetries drop with redshift as faint outer regions fade

True z vs. simulated z=3 asymmetries Median asymmetry in z=3 simulation: A med <0.1 (vs. 0.3 for original images)

Conclusions HIIGs and LCBGs are smaller, lower-L than LBGs, but with similar morphologies, asymmetries, colors, star formation properties. Masses of HIIGs and LCBGs are small, M<10 10 M; many LBGs may be too. Caveats: Fate of LBGs not known; difficult to constrain masses of LBGs for comparison Still to come: better morphological analysis (e.g., Gini coefficient, Lotz et al. 2004)