T HE CGM AS A T ESTBED FOR F EEDBACK - R EGULATED G ALAXY F ORMATION - PowerPoint PPT Presentation

T HE CGM AS A T ESTBED FOR F EEDBACK - R EGULATED G ALAXY F ORMATION P IERO M ADAU UCSC, IAP

A fully predictive theory of Galaxy Formation remains one of the great, unsolved problems of Astrophysics. Modern Cosmological Galaxy Formation is about understanding: DM Particle • the mapping between dark matter halos and their baryonic Physics luminous components; • galaxy metabolism and the basic processes of gas ingestion (infall and cooling), digestion (star formation/feedback), and Collisionless excretion (outflows); Dynamics • galaxy color and structural bimodality ; • the epoch of first light, metal enrichment, and cosmic reionization. Hydrodynamics Stellar Feedback Star Formation Atomic Cooling AGN Feedback Radiative Transfer

Over the past two decades, an avalanche of new data from multi-wavelength imaging and spectroscopic surveys has revolutionized our view of galaxy formation and evolution. Almost by definition, what we saw has whetted our appetite for more data and theory ; some problems have been solved , some have been re-named. And while there is general agreement on the basic ingredients of galaxy formation: accretion of baryons from the IGM via inflows and mergers, the transport of hierarchical build-up of DM halos, generation of angular momentum angular momentum, gas cooling and via tidal torques condensation, star formation and feedback …

…there is little consensus on anything else: • Dark Matter : Cold, Warm, Self-Interacting, Fuzzy, Not Even There? • Mass Density Profiles : Cored or Cuspy? • Gaseous Assembly : Cold vs Hot Accretion, Smooth/Clumpy/Filamentary, How Much Wind Recycling? • Numerical Technique : Hydro Solver, Softening, Convergence, MBTY Syndrome • Star Formation : Need for H 2 , Metallicity-Dependent, Impact of Turbulence/ Magnetic Fields? • Stellar Feedback : Algorithm, Momentum or Thermal, Radiation Pressure, Ejective or Preventive, Cosmic Rays? • AGN Activity/Feeback: Radiative or Mechanical, Local or Global, Intermittent or Persistent, Self-Regulated or Stuff Simply Happens, Role in Quenching? • Galactic Winds : Mass-Loading, Z-loading, How Far, Episodic or Steady, Gas Coming-in vs Going-out, Where Does Ejected Gas Go?

Over the last two decades the word circumgalactic/CGM has gone from being a term mostly used by Matt Lehnert … …and in the science fiction literature… “Christmas 2071: Mars and Venus are colonized. It is 45 years since the submarine Pegasus , laden with nuclear missiles, was jettisoned into space – After completing its circumgalactic orbit, it’s back!” …and in the health sciences …

…to a field of study that holds clues to understanding the exchange of mass, metals, and energy between galaxies and their surroundings, the response of baryons to DM potential wells, the (in)efficiency of star formation, the nature of feedback. Inflows along filaments, lower Accreting Z or pristine 10 9.7 M ⦿ DG A theorist view of the CGM of a massive star-forming (18 M ⦿ /yr) galaxy at z=3! Virial radius of Outflows ⊥ the 10 11.4 M ⦿ to disk high Z host galaxy Shen et al 2013

Ε RIS : A P ROTOTYPE OF N EW G ENERATION H YDRO S IMULATIONS cosmological SPH simulation with zoom-in ICs 10pc hydro resolution low-T metal-line cooling UVB heating & photoionization SN blastwave feedback (delayed radiative cooling) high SF gas density threshold (>50x higher than old standard sims) ➩ SF is clustered

A H OLISTIC A PPROACH TO G ALAXY M ETABOLISM Pizagno et al. 2007 Eris (z=0) Eris SDSS blue HB stars (Xue et al. 2008) DM Stars Gas Spheroid Disk B/D = 0.35 (typical of Sb-Sbc) n=1.4 R d = 2.5 kpc

S HAPE OF G RAVITATIONAL P OTENTIAL Pal 5+E RIS Dai et al. 2017 Remarkable consistency Bovy et al. 2016 between inner (20 kpc) potential of E RIS and that of the Milky Way E RIS — MW — SFR [M ⦿ yr − 1 ] SF H ISTORY OF S TELLAR D ISK Reconstruction of SFH of the Milky Way disk from chemical abundances (Snaith et al 2015). Lookback Time [Gyr]

I NTERSTELLAR A BSORPTION -L INE S TRENGTHS ( z~3 ) Shen et al. 2014 rest-frame equivalent width (Å) Keck Baryonic Structure Survey deficit of cold enriched CGM spikes = satellites impact parameter b/R vir impact parameter b/R vir • Density of black points = measurement of covering factor of absorbing gas at given b . • At small impact parameters lines are mostly saturated and W 0 is modulated by the velocity structure of absorbing material.

W HAT IS THE C OVERING F ACTOR ? Rudie et al. 2012 HI CIV CII OVI M O (CGM) ~ 5e7 M ⦿ > M O (ISM)

W HAT IS THE O RIGIN OF THE CGM ( Z>0, R<3R VIR )? Three sources of heavy elements: (1) the main host , responsible for 60% of all the metals found within 3 R vir ; (2) its satellite progenitors , which shed their metals before and during infall, and are responsible for 30% of all the metals within 3 R vir , and for 5% of those beyond 3 R vir ; (3) nearby dwarfs , which give origin to 10% of all the metals within 3 R vir and 95% of those beyond 3 R vir . Metal Mass Fraction M ETALS M OSTLY C OLD , W ARM , OR H OT ? Redshift

W HEN WAS CGM E NRICHED ? Late (z < 5) galactic superwinds – the result of recent star formation in E RIS – account for only 9% of all the metals observed beyond 2R vir , the bulk having been released at redshifts 5<z<8 by early star formation and outflows.

M ETALLICITY OF I NFLOWING C OLD M ATERIAL ? 16.1< log N HI <18.6 z=3 H I total cold mode Frequency accretion inflowing LLSs log Z/Z ⦿ C II Lehner et al 2017 Frequency log Z/Z ⦿

M ETALLICITY D ISTRIBUTION AROUND D WARFS ? • Accretion onto DGs is generally not along filaments. • Outflows are more disruptive. • LLS metallicity distribution consistent with being unimodal. z=3 16.1< log N HI <18.6 Frequency total inflowing LLSs Courtesy of S. Shen log Z/Z ⦿

H OW D OES THE CGM E VOLVE ? OVI 500 pkpc O VI z = 2 z = 1 z = 0.5 z = 2.8 z = 3 • O VI halo grows with time, large O VI column densities maintained within R vir. • Covering factor of log N OVI > 13 z=3.0 I V O absorption within R vir remains ~ N z=1.0 z=2.0 g unity at all redshifts. o l • Simulation results appear z=0.5 consistent with observations of star-forming galaxies. impact parameter b/R vir

W HERE ARE THE M ISSING B ARYONS ? There are ~ no missing baryons within ~ 2 R vir on massive galaxy scales! disk 35% M b Sokolowska et al 2016

SZ AS A P ROBE OF THE G AS C ONTENT OF DM H ALOS Planck Collaboration 2013 “…Gas properties of DM halos appear remarkably regular over a mass range where cooling and feedback processes are expected to vary strongly…The fact that the signal is close to the self-similar prediction implies that Planck-detected hot gas represents roughly the mean cosmic fraction of the mass even in such low-mass systems”…

T HE G ALAXY ’ S HI V EIL …. The High-Velocity 21-cm Sky (Richter et al 2017) H α absorption map (Zhang et al 2017)

VS . S IMULATIONS 10 7 200 10 6 10 5 100 10 4 log 10 gcm − 3 10 3 y / kpc 10 2 0 10 1 10 0 − 100 10 − 1 10 − 2 − 200 10 − 3 M HI = 2e9 M ⦿ − 200 − 100 0 100 200 x / kpc

A T HEORY OF CGM: G ALAXIES AS H EAT E NGINES log Z/Z ⦿ Gas expands and cools Isobaric radiatively n~1/T CGM Gas cooling and condensation Heated IGM outflowing gas ISM

C YCLE OF M ETAL -E NRICHED G AS IN THE 𝞻 -T P LANE E RIS z=0 D WARF G ALAXY n H T n H z=3 n H T n H

“Complex problems have simple, easy to understand, wrong solutions.” T. Gold