Extreme Emission Line Galaxiesin the early universe(and their cousins

at intermediate redshift)

Dominik J. Bomans

Astronomical Institute of the Ruhr-University Bochumand

Ruhr-University Bochum Research Department “Plasmas with complex interactions”

With significant contributions from

Marianne Langener

and input from

Carolina Kehrig, Pepe Vilchez, Ana Monreal-Ibero, Kerstin Weis, and Polis Papaderos

When do first galaxies form?

Pawlik et al. (2013)

z=19 z=16 z=13

Gas density

Gas temperature

Already around z=20 first galaxies could form...

(proto-)galaxy formation

Log gas density [cm-3]

Log metallicity [Z/H]

Simulation snapshot of dwarf/proto-galaxy at z=17Box size 8.6x8.6 kpc Wise & Abel (2008)

Version adapted by Bromm & Yoshida 2011

Feedback:- Radiation- Stellar winds- Supernovae

→ extended and high density Ionized gas regions

Direct observational evidence

Several 7-10 (proto-)galaxyCandidate in last 2 years

Current record example:Lensed z~11 candidatedwarf/proto-galaxy

Requires HST&WF3and lensing from a “cosmictelescope”

Coe et al. (2012)

Fossile record

Weisz et al. (2011)

Color magnitude diagram analysis

Many dwarf galaxies are behind the cosmic average in forming stars between z~0.7 and z~0.1→ not participating in downsizing?? or are the Local Volume dwarf galaxies special?

At high redshift: big error bars...

Skillman (2005)

Fossile record

Cole et al. (2007)

Leo Amost star formation late...

Are there dwarf galaxies with their biggests (first?) bursts at intermediate redshifts?

Local metal-poor dwarf galaxies

SBS0335-052 HST B,V,Hα color composite(Bomans, in prep.)

Morales-Luis et al. 2011

Very blue

Strong emission lines

Dwarf galaxy in formation?UGC 5340

Voigtländer, Bomans, Moiseev et al. 2011, and in prep.

Dynamically not relaxed?

Could be infall and outflows mixed

Extreme emission line galaxiesUltra Strong Emission line galaxies (USELs) (Kakazu et al. 2007, Hu et al. 2009) z~0.5

Green Peas (Cardamone et al. 2009) z~0.05

Very Stong Emission line galaxies (Atek et al. 2012, van der Wel et al. 2012) z~1.7…

Atek et al. (2012)→ strong bursts in small, partly metal-poor galaxies

Strange colors ...

Atek et al. (2012)

Emission lines dominate the broad bandFluxes and colors

Hunting techniques

Emission Line imaging (e.g. Kakazu et al. 2007)HST slitless spectroscopy (e.g. Atek et al. 2011)Data mining in large surveys (e.g. Cardamone et al. 2009)“Impossible” broad band colors (e.g. Brown et al. 2008)

But intrinsic blue colors have not be explored yet...

Starburst99 Instantaneous burst Barazza et al. (2006)

Hunting unevolved galaxies

Langener & Bomans, in prep

Population of extremely blue dwarf galaxies

Extremely blue rest frame colors due to very blue continuum, not emission lines→ very low metallcity?→ recent strong burst→ small or no older, red

stellar population

CDFS:MUSYC optical/NIR multiband data+ GALEX + HST

→ select dwarf sample with photo-z and rest-frame parameters

→ VLT spectra

What are they?

Dwarf galaxies at intermediate redshift !

Langener & Bomans, in prep

What are they?

→ dwarf galaxies at intermediate redshift

→ compact strong emission line objects, low to very low metallicity !

VLT spectrum (rest frame) and HST g-band image (5”x5”) of one of our extremely blue dwarf galaxies.The metallicity is [O/H] < 7.6 !

Langener & Bomans, in prep

Deviants in [O/H] – L plane

Adapted from Brown et al. (2008)Detection from previous slide

Evolution in [O/H] – Lum. plane ?

Adapted from Hu et al. (2009)

Detection from previous slide

Conclusions

● Strong emission line dwarf galaxies are metal poor starbursts

● They exist out to at least z~2, which shows existance of a population of late-bloomers, as a Leo A CMD study indicated

● Extreme blue colors can be used to select most extreme cases

● Location in the metallicity-luminosity plane indicate unevolved state, close to properties of assumed first galaxies in universe

● More spectra being analyzed, more fields in work (COSMOS, HDF-N, AEGIS)

Nearby very low metallicity strong emission line galaxies provide laboratory for physics of galaxy formation and evolution

Thank you for your attention !