“Local Lyman Break Galaxy Analogs: The Impact of Massive Star-Forming Clumps on the Interstellar Medium and the Global Structure of Young, Forming Galaxies”

2 Contents “Local Lyman Break Galaxy Analogs: The Impact of Massive Star-Forming Clumps on the Interstellar Medium and the Global Structure of Young, Forming Galaxies” Overzier et al. 2009, ApJ, 706, 203 Comparison of LBAs and High-z Galaxies (including sBzK galaxies by MOIRCS)

“Local Lyman Break Galaxy Analogs: The Impact of Massive Star-Forming Clumps on the Interstellar Medium and the Global Structure of Young, Forming Galaxies”

4 LBGs: “Lyman Break Galaxies” UV-selected galaxies at z~3 our most detailed information about star formation in the early universe has been provided by UV-selected galaxies Adelberger et al. 2004

5 LBAs: “Lyman Break Analogs” “living fossils” of LBGs star-forming galaxies selected from the UV imaging survey by GALEX (GR1; Martin et al. 2005) + SDSS (DR3; Abazajian et al. 2005) ● UVLGs (UltraViolet Luminous Galaxies) : L FUV (1530 Å ) > L ◎ ➢ L * for LBG at z~3 = L ◎ ● supercompact UVLGs: I FUV > 10 9 L ◎ kpc -2 ● 35 samples (30 for this paper) from 450 deg 2, z<0.3 ➢ 〜 Mpc -3 rare! LBA s

6 LBAs: “Lyman Break Analogs” supercompact UVLGs (=LBAs) have characteristics remarkably similar to Lyman break galaxies (Hoopes et al. 2007) Hoopes et al. 2007

7 “clumpy” mode star formation ● observations with the HST indicate that star formation largely occurs in an extremely clumpy and compact mode ➢ clumps with masses M ◎ and sizes of > 1kpc are very typical constituent of extended irregular galaxies at z=1-4 in the UDF (Elmegreen et al. 2009) ➢ from simulation, clump systems would evolve into galaxy bulges and/or supermassive nuclear black holes (Noguchi 1999; Immeli et al. 2004; Elmegreen et al. 2008a, 2008b) Elmegreen et al. 2009

8 UV-Optical Morphologies □: DCO (Dominant Central Object) host galaxies

9 Stellar Mass & Ages of Clumps stellar population parameters of clumps and DCOs ● extinction: Balmer decrement (f Hα /f Hβ ) with a constant relation between reddening of gas and the stellar continuum (Calzetti 2001) ● stellar synthesis models (Starburst99 5.1; Vazquez & Leitherer 2005) ➢ stellar mass ～ M ◎ ➢ ages ～ 5 – 100 Myr (instantaneous starburst); 100 – 1000 Myr (continuous SFH); sensitive to SFH ●: instantaneous starburst ●: continuous SFH

10 Clump Sizes ● DCOs are marginally resolved at best ● compare the observed radial profiles (plus signs) with Gausian models convolved with model PSF using TinyTim 3.0 software (Krist 1995) (colored solid lines; 0".005-0".125 FWHM) ➢ observed data are consistent with ～ 0".075 (FWHM)

11 The Relation between Clumps and Their Host Galaxies Star Formation Rates ● Hα: dust corrected emission from ionized region (Calzetti 2001) ● uncorrected Hα+24μm: attenuated emission from ionized region + dust emission heated by young stars (Calzetti et al. 2007) ● FUV: UV continuum from young stars ➢ (Treyer et al. 2007) ➢ for a K-correction of l 1500 Å

12 The relation between Clumps and Their Host Galaxies Star Formation Rates ● all the three indicators agree to within a factor of ～ 2 to 3 ● Hα SFRs are significantly lower than either both or one of the other two SFRs. ➢ aged starburst?; the ratio of ionizing/non-ionizing UV falls for ages >5-6Myr ➢ leaky starburst?; kinetic energy from ～ 10 7 SNe within the small volume of DCOs may create large holes in the ISM to escape ionizing photons ➢...but non-ionizing UV photons are absorbed by dust to heat them?? ■: DCOs □: clumps

13 The Relation between Clumps and Their Host Galaxies absolute B-band magnitudes and other properties

14 Emission Line Properties type-I AGN ● direct view of the accretion disk and broad emission line region? ➢ no obvious broad ( ～ 1000kms -1 ) Balmer emission lines ● relatively broad blue-shifted component; blue wing ➢ signposts of galactic winds, which are commonly observed in intense starbursts

15 Emission Line Properties type-II AGN ● [NII]-Hα vs [OIII]-Hβ diagram ➢ observable out to z<3 ● BPT displacement ➢ also shown in intensely star- forming galaxies at high-z (BM/BX, DRGs, sBzKs...) ➢ physical mechanisms are not known ● DCOs harbor a type-II AGN?

16 Emission Line Properties Other diagnostic diagrams ● DCOs are not classified to AGN, but to “no man's land” ➢ similar behavior is seen in local IR-warm starbursts (Kewley et al. 2001)

17 Emission Line Properties The Aged Starburst Hypothesis ● for instantaneous starburst with age Myr, mechanical energies are supplied by SNe rather than O-stars; shock-heated gas ➢ enhancement in [OIII]/Hβ and [NII]/Hα ➢ high electron density & blue wings ➢ but fails to explain weakness of [SII] and [OI] The Leaky Starburst Hypothesis ● large holes in the ISM to escape ionizing photons ➢ [OI] and [SII] lines relative to Hα are decreased ➢ [OIII]/Hβ is enhanced, but [NII]/Hα is lower spatially resolved spectra are needed to distinguish the line emission by clumps from those by diffuse regions

18 Structural Properties Super Star Clusters ● typical size ～ a few pc, masses < 10 7 M ◎ ➢ DCOs ～ 100pc, masses ～ M ◎ ➢ mass surface densities are comparable → scaled up version? ● multiple SSCs ➢ velocity dispersion σ clump ～ (GM clump /5R e ) -1/2 ～ 30kms -1 ➢ timescale for a single SSC to migrate inward ～ 10-20Myr ～ age of clumps very different structurally from typical SSCs

19 Structural Properties Extra Light and Central “Cusps” ● central cusp: the remnant signature of a massive central starburst in a dissipative (“wet”) merger ➢ DCOs have similar correlation between M * and Σ e (Kormendy relation), R e and Σ e

20 Summary DCOs and other LBAs ● DCOs are more massive, more concentrated, and more actively forming stars than the other LBAs ● DCOs have BPT displacement from local star-forming galaxies ● Hα SFRs are lower than either both or one of UV or IR SFRs AGN ● broad Balmer lines are not found (not type-I) ● BPT diagram probably suggests DCOs host type-II Emission Lines ● dominated by young stars; leaky starburst? Structures ● different from typical super star clusters ● consistent with signposts of merger (cusps, optical images)

Comparison of LBAs and High-z Galaxies (including sBzK galaxies by MOIRCS)

22 Stellar Mass and SFR ● LBA and BM/BX (UV-selected) occupy similar region on M * -SFR plane ● sBzK galaxies have larger SFRs for given stellar masses

23 BPT diagram ● stacked emission lines of sBzKs also have BPT displacement ● the locus on BPT diagram is similar to that of BM/BX and LBAs?

24 Mass-Metallicity Relation ● low-mass (and high-SSFR) sBzKs have higher metallicities for a given stellar mass ● the metallicities are comparable to local SDSS galaxies (z~0) ● LBAs (z~0) and BM/BX galaxies (z~2) have similar mass-metallicity relation ● UV-selected and (a part of ?) optical-selected galaxies are at different stages of star formation? (Overzier et al. astro- ph/ )

25 K-band images of low-SSFR sBzKs low-SSFR sBzKs are compact?? Yoshikawa 2009, PhD thesis 3".5 on a side

26 K-band images of high-SSFR sBzKs

any question?

28 Dust Attenuation

29 Mass-Metallicity Relation

30 Metallicity and Surface Brightness

31 BPT Diagram