Benjamin D. OppenheimerLeiden Observatory

Sensitive Barometers of Galaxy Formation

Simone Weinmann, Romeel Dave, Kristian Finlator, Jason Tumlinson, Rob Crain &

others

Are Flat or Rising Star Formation Histories in Dwarfs (Low-Mass Centrals) Required?

Abundance matching- Behroozi et al. (2012)

Main Sequence Integration- Leitner (2012)

VESPA SSP Modelling- Tojeiro et al. (2009)

Stellar Mass Assembly Histories Are Diverse, DM Accretion Histories Not So Much

Behroozi, Wechsler, & Conroy 2o12

SFHs independent of ΛCDM dark matter assembly are difficult to reproduce in SAMs and simulations (Weinmann et al. 2012).

Simulated and SAM SFHs Assemble Dwarfs Way Too Early (It Seems).“The overproduction of low-mass galaxies at z > 0.5 in all SAMs and hydrodynamical simulations explored here may thus be symptomatic of the limited range of feedback prescriptions currently in use, and indicates that alternative models of feedback need to be explored.”

--Weinmann et al. (2012)

Weinmann et al. (2012)

Wind Mode: A Way to Separate SFHs from DM Accretion Histories?

Opp. et al. 2010

All Assemblyw/ wind mode

W/O Wind Mode

Opp. et al. 2010

We separated stellar assembly based on whether stars formed from pristine, cold accretion or re-accreted winds accreted from the circumgalactic medium (CGM).

Recycling Winds Assembles Mass in Dwarf Centrals at Late Times

Opp. et al. 2010

All Assemblyw/ wind mode

W/O Wind Mode

Opp. et al. 2010

Wind recycling is a way of moving stellar mass assembly to late times via cycles through the circum-galactic medium (CGM).

Weinmann et al. (2012)

M*=109.27-109.77 Msol

The Money Plot… Literally.Oppenheimer-style resolution of the same 1011.2 Msol halo

129 orbits to observe the CGM of z=0-0.1 dwarfs at 20-150 kpcs (PI J. Tumlinson)

We Are Searching for the Baryons Missing from Stellar Assembly in Dwarf Halos

No Winds: No Metals in CGM, most baryons form into stars.

Fast Winds: 700 km/s blows most baryons out of CGM, only a cool few metals left behind

Momentum-driven Winds: slower winds, 100-200 km/s, keep baryons recycling and participating in galaxy formation, plenty of cool metals.

REAL DATA NEW RESULTS!!: CIV Covering Fractions From COS-Dwarfs

Thanks to Rongmon Bordoloi & Jason Tumlinson.

ezw is the new vzw*

Energy-conserved feedback (ezw) where vwind ~ σ, η ~ 1/σ2 where low-mass galaxies are suppressed more than momentum-conserved feedback (vzw): η ~ 1/σ.

Missing baryons are ejected into the CGMs of these halos.

*Let’s hope not.

CGM

CGMC

GM

More Mass-Loading for Dwarfs Could Alter Stellar Assembly Histories

14 Gyrs 1 Gyr

vzw: η ~ 1/σ

14 Gyrs 1 Gyr

ezw: η ~ 1/σ2

Macc×fb

Msf cold

Msf wind

Early winds suppress SF relative to baryon accretion rate. Returning winds that recycle on timescales of Gyrs add to late time stellar assembly, increasing late time specific SFR’s.

Wind Recycling is Capable of sSFR Downsizing

Wind recycling returns material back onto dwarf galaxies raising the sSFR’s for lower mass galaxies at late times (z=0).

Mystery of Galaxy Formation May Be Solved

“I think it's possible that Simone's dwarf SFH problem will disappear given the new wind model plus the new faint-end data which is steeper at high-z.”

--Romeel Davé

Diversity in Star Formation Histories is Possible Via Wind Recycling

Cold ModeHot ModeWind Mode

Diversity in Star Formation Histories is Possible Via Wind Recycling

Cold ModeHot ModeWind Mode

Summary Points1. The shallow potential wells of low-mass

halos are very sensitive testbeds for feedback processes affecting galaxy formation.

2. We are banking on finding a large fraction of the low-mass halo missing baryons in their local CGMs, where launched winds can re-participate in late galaxy formation.

3. Putting in 2-3 new, non-traditional parameters into SAMs (e.g. recyling parameters) should be able to divorce stellar assembly histories from dark matter accretion histories and reproduce most key observations of low-mass galaxy formation.

New Tests for Galaxy Formation Models

Patel et al. (2013)

Are our simulations building the right galaxies in the right halos at the right time?

Behroozi et al. 2012: star formation rate divided by baryon accretion rate for halos of various masses from z=8->0.

Are our simulations building the right galaxies in the right halos at the right time?

Behroozi et al. 2012: star formation rate divided by baryon accretion rate for halos of various masses from z=8->0.

Are our simulations building the right galaxies in the right halos at the right time?

Behroozi et al. 2012: star formation rate divided by baryon accretion rate for halos of various masses from z=8->0.

Are our simulations building the right galaxies in the right halos at the right time?

Behroozi et al. 2012: star formation rate divided by baryon accretion rate for halos of various masses from z=8->0.