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

PIERO MADAU UCSC, IAP

THE CGM AS A TESTBED FOR FEEDBACK- REGULATED GALAXY FORMATION

A fully predictive theory of Galaxy Formation remains one of the great, unsolved problems of Astrophysics. Modern Cosmological Galaxy Formation is about understanding:

• the mapping between dark matter halos and their baryonic

luminous components;

• galaxy metabolism and the basic processes of gas ingestion

(infall and cooling), digestion (star formation/feedback), and excretion (outflows);

• galaxy color and structural bimodality;
• the epoch of first light, metal enrichment, and cosmic

reionization.

DM Particle Physics Collisionless Dynamics Hydrodynamics Atomic Cooling Star Formation Radiative Transfer

Stellar Feedback

AGN Feedback

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: hierarchical build-up of DM halos, generation of angular momentum via tidal torques accretion of baryons from the IGM via inflows and mergers, the transport of angular momentum, gas cooling and condensation, star formation and feedback…

• 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 H2, 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? …there is little consensus on anything else:

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 Z or pristine

Outflows ⊥ to disk high Z Accreting 109.7 M⦿ DG

A theorist view of the CGM of a massive star-forming (18 M⦿/yr) galaxy at z=3!

Virial radius of the 1011.4 M⦿ host galaxy

Shen et al 2013

ΕRIS: A PROTOTYPE OF NEW GENERATION HYDRO SIMULATIONS

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

Eris (z=0)

Gas Stars DM

SDSS blue HB stars (Xue et al. 2008)

A HOLISTIC APPROACH TO GALAXY METABOLISM

Pizagno et al. 2007 Eris

B/D = 0.35 (typical

• f Sb-Sbc)

n=1.4 Rd = 2.5 kpc

Spheroid Disk

Bovy et al. 2016

SHAPE OF GRAVITATIONAL POTENTIAL SF HISTORY OF STELLAR DISK

Dai et al. 2017

ERIS — MW —

SFR [M⦿yr−1] Lookback Time [Gyr]

Pal 5+ERIS

Reconstruction of SFH of the Milky Way disk from chemical abundances (Snaith et al 2015). Remarkable consistency between inner (20 kpc) potential of ERIS and that

• f the Milky

Way

impact parameter b/Rvir impact parameter b/Rvir

Keck Baryonic Structure Survey

rest-frame equivalent width (Å)

INTERSTELLAR ABSORPTION-LINE STRENGTHS (z~3)

• Density of black points = measurement of covering factor of absorbing gas at given b.
• At small impact parameters lines are mostly saturated and W0 is modulated by the

velocity structure of absorbing material.

spikes = satellites deficit of cold enriched CGM

Shen et al. 2014

HI CII CIV OVI

WHAT IS THE COVERING FACTOR?

Rudie et al. 2012

MO(CGM) ~5e7 M⦿ > MO(ISM)

WHAT IS THE ORIGIN OF THE CGM (Z>0, R<3RVIR)?

Three sources of heavy elements: (1) the main host, responsible for 60% of all the metals found within 3Rvir; (2) its satellite progenitors, which shed their metals before and during infall, and are responsible for 30% of all the metals within 3Rvir, and for 5% of those beyond 3Rvir; (3) nearby dwarfs, which give origin to 10% of all the metals within 3Rvir and 95%

• f those beyond 3Rvir.

METALS MOSTLY COLD, WARM, OR HOT?

Metal Mass Fraction

Redshift

Late (z < 5) galactic superwinds – the result of recent star formation in ERIS – account for only 9% of all the metals observed beyond 2Rvir, the bulk having been released at redshifts 5<z<8 by early star formation and outflows.

WHEN WAS CGM ENRICHED?

H I C II

Frequency log Z/Z⦿ inflowing LLSs

z=3

log Z/Z⦿ Frequency

Lehner et al 2017

METALLICITY OF INFLOWING COLD MATERIAL?

cold mode accretion total

16.1< log NHI <18.6

METALLICITY DISTRIBUTION AROUND DWARFS?

• Accretion onto DGs is generally not

along filaments.

• Outflows are more disruptive.
• LLS metallicity distribution consistent

with being unimodal. z=3

Frequency

inflowing LLSs total

log Z/Z⦿

16.1< log NHI <18.6 Courtesy of S. Shen

HOW DOES THE CGM EVOLVE? OVI

z = 2.8

z = 3 z = 2 z = 1 z = 0.5 l

• g

N

O V I

O VI

z=3.0 z=2.0 z=1.0 z=0.5

impact parameter b/Rvir

O VI

500 pkpc

• O

VI halo grows with time, large column densities maintained within Rvir.

• Covering factor of log NOVI > 13

absorption within Rvir remains ~ unity at all redshifts.

• Simulation results appear

consistent with observations of star-forming galaxies.

WHERE ARE THE MISSING BARYONS?

There are ~ no missing baryons within ~2Rvir on massive galaxy scales!

disk

Sokolowska et al 2016 35% Mb

SZ AS A PROBE OF THE GAS CONTENT OF DM HALOS

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”…

Hα absorption map (Zhang et al 2017) The High-Velocity 21-cm Sky (Richter et al 2017)

THE GALAXY’S HI VEIL….

−200 −100 100 200 x/kpc −200 −100 100 200 y/kpc 10−3 10−2 10−1 100 101 102 103 104 105 106 107 log10 gcm−3

MHI=2e9 M⦿

• VS. SIMULATIONS

A THEORY OF CGM: GALAXIES AS HEAT ENGINES

CGM

IGM

Gas cooling and condensation

ISM

log Z/Z⦿ Heated

• utflowing gas

Isobaric n~1/T Gas expands and cools radiatively

CYCLE OF METAL-ENRICHED GAS IN THE 𝞻-T PLANE

z=0 z=3

nH nH nH T nH T ERIS

DWARF GALAXY

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

• T. Gold