Constraining the Physical Processes that Shape the CGM (at low - PowerPoint PPT Presentation

Constraining the Physical Processes that Shape the CGM (at low redshift) Arguments will follow Werk et al. 2016 and McQuinn & Werk 2017: What Matter(s) Around Galaxies, Durham University, June 2017

Broadly Speaking, the low-z CGM is a metal-enriched, bound, massive reservoir of multiphase galactic baryons. What is the origin and fate of the CGM, and what physical properties shape it? What Matter(s) Around Galaxies, Durham University, June 2017 2

Part 1: Top 10 Observed Properties of the Low-z CGM A viable model must be able to account for observed features (in CGM of L* Star-forming Galaxies) Funny graphic? What Matter(s) Around Galaxies, Durham University, June 2017 3

Observation #1: OVI is Ubiquitous Around Star Forming Galaxies N OVI ≈ 10 14.5 cm -2 COS-Halos Implies NFW Dark Matter What Matter(s) Around Galaxies, Durham University, June 2017

Observation #2: Suprathermal Line Widths Unresolved, b < 15 km.s b th , OVI, 10 5.5 K ≈ 18 km/s 𝑐 #$ , 𝑃𝑊𝐽 ≈ 40 − 50 𝑙𝑛 𝑡 12 𝑐 #$ , 𝑇𝑗𝐽𝐽𝐽 < 20 𝑙𝑛 𝑡 12 Caveat: possible blending of many narrow components with offsets < 10 km s -1 Werk+16 What Matter(s) Around Galaxies, Durham University, June 2017

Observation #3: Coincident Line Centroids Low Ions: ∆𝑤 ≈ 0 𝑙𝑛 𝑡 12 OVI: ∆𝑤 ≈ 5 ± 3 𝑙𝑛 𝑡 12 NB: excludes 20% of OVI absorption, i.e. That which occurs without any lowions – aka no-lows Werk+16 What Matter(s) Around Galaxies, Durham University, June 2017

− Observation #3: Coincident Line Centroids − J1112+3539 − 236_14 1. “Narrow” OVI corresponds well with J1016+4706 narrow low-ions (40%) 359_16 J1016+4706 2. “Broad” OVI corresponds well with 274_6 narrow low-ions (40%) J1009+0713 − 170_9 3. OVI with no low-ion matches within J1009+0713 +/- 50 km/s (20% “No-lows”) 204_17 J0401 − 0540 67_24 -300 0 300 v (km/s) Werk+16 − What Matter(s) Around Galaxies, Durham University, June 2017

Observation #4: Small Kinematic Offsets from Hosts ∆𝑤 ~50 − 150 𝑙𝑛 𝑡 12 no-lows in halos 𝑁 >?@A ≲ 10 2C 𝑁 ⨀ Werk+16 What Matter(s) Around Galaxies, Durham University, June 2017

Observation #5: Massive Reservoir of Photoionized ~10 4 K Gas Ω m /Ω b = 0.16 ; M halo = 10 12.2 M ⊙ Gripe about the details, but we actually all agree on a very basic level: Werk+14 Prochaska et al. 2011: 𝑁 E>A$A ≥ 10 2G 𝑁 ⨀ Stocke et al. 2013: 𝑁 E>A$A ≥ 10 2G 𝑁 ⨀ Werk et al. 2014: 𝑁 E>A$A ≥ 10 2G 𝑁 ⨀ Stern et al. 2016: 𝑁 E>A$A ≥ 10 2G 𝑁 ⨀ Prochaska+17 Prochaska et al. 2017: 𝑁 E>A$A ≥ 10 2G 𝑁 ⨀ Keeney et al. 2017: 𝑁 E>A$A ≥ 10 2G 𝑁 ⨀ NB: Low densities unavoidable 𝑜 E>A$A ≲ 10 1C.J 𝑑𝑛 1L What Matter(s) Around Galaxies, Durham University, June 2017

Observation #6: Gas is not Pristine Mean L* 𝑎 NOP ≈ 0.3 𝑎 ⨀ 25% of the sample has > 50% of their PDFs > 𝑎 ⨀ ! The super solar gas lies at R > 75 kpc Prochaska+17 What Matter(s) Around Galaxies, Durham University, June 2017

Observation #7: Upper limits on NV/OVI Rules out Photoionization of OVI by UVB only COS-Halos Stacked Data for Star-forming Galaxies Good coverage of NV doublet…yet rarely detected. Werk+16

Observation #7: Upper limits on NV/OVI Rules out Photoionization of OVI by UVB only Log L min (kpc) 5 4 3 2 1 0.5 0.5 • Observations require Log U ≪ -1 1 0.0 0.0 − 2.0 • Conservative assumptions (i.e., solar 4 − 1.5 3 Log N NV /N OVI − 0.5 − 0.5 metallicity) give L >> 100 kpc 6 − 1.0 10 − 1.0 − 1.0 7 • For path lengths such as these one − 0.5 4 would not expect coherence in velocity 2 − 1.5 − 1.5 PIE, HM01 structure between OVI and low-ions 1 (i.e. narrow OVI!). − 2.0 − 2.0 − 7 − 7 − 6 − 6 − 5 − 5 − 4 − 4 − 3 − 3 Log n h (cm − 3 ) Werk+16

Observation #8: Low gas densities of 10 4 K material 10 5 NB: 10 − 3 Corrected 10 4 from Werk+14 n H /<n H > n H cm − 3 by factor of 4 10 3 for HM2001; 10 − 4 HM2012 roughly 10 2 consistent 10 − 5 with Werk+14 10 1 0.1 1.0 R/R vir Derived gas volume densities are greater than an order of magnitude lower than predictions from standard two-phase models in which cool clouds are in pressure equilibrium with hot, coronal gas (Werk+14) 13

Observation #9: Red galaxies have HI but infrequently show OVI absorption in CGM SFR > 0.1 M ⊙ yr -1 20 (blue, star-forming) 15.0 SFR < 0.05 M ⊙ yr -1 18 (red, quiescent) Log N HI [cm − 2 ] Log N OVI [cm − 2 ] 14.5 16 14.0 13.5 14 13.0 12 0 50 100 150 200 − 13 − 12 − 11 − 10 − 9 − 8 ρ [kpc] Log sSFR [ yr − 1 ] Quenching appears to modify the abundance of high ions in L* halos while leaving the low ions mostly unaffected (Tumlinson+11) 14

Observation #10: Uniform OVI velocity dispersion The kinematics of OVI absorbers are similar regardless of galaxy color, azimuthal angle, and inclination. Pixel-velocity two point correlation function using MAGIICAT data Nielsen+17; but see Kacprzak+15

Part 2: One Viable Model Consistent with Top 10 Observed Features of the L* CGM NB: Read McQuinn & Werk 2017 to see all the models we can rule out! Including: fast shocks, hot winds, OVI photoionized by UVB and in thermal equilibrium See also McCourt et al. 2012 What Matter(s) Around Galaxies, Durham University, June 2017 16

OVI Represents A Massive Cooling Flow Assume: 1. OVI is transitioning through 10 5.5 K 2. 𝑢 TUV = 𝑢 XAA@ (isobaric cooling time) where → McQuinn & Werk 2017 What Matter(s) Around Galaxies, Durham University, June 2017

OVI Represents A Massive Cooling Flow Assume: 1. OVI is transitioning through 10 5.5 K 2. 𝑢 TUV = 𝑢 XAA@ (isobaric cooling time) Higher pressure, higher mass flux. Higher metallicity, lower mass flux To generate the observed N OVI requires fluxes into the 10 5.5 K phase of many tens of solar masses per year. McQuinn & Werk 2017 What Matter(s) Around Galaxies, Durham University, June 2017

The Behavior of an Isobaric Cooling Flow ≈ The mass participating in these flows must be 10 22 𝑁 ⨀ , similar to the total baryonic mass for an L* halo. Model tuned to yield 𝑂 TUV ≈ 3 × 10 2\ 𝑑𝑛 1C McQuinn & Werk 2017 What Matter(s) Around Galaxies, Durham University, June 2017

Implications of the Cooling Flow Model Thermal pressure bounds Energetics Cooling within age Energetics of Universe from considerations 10 6 K Star formation? 𝐹̇ _`# ~ 10 49 – 50 erg yr -1 AGN? (flickering? Talk to Ben O.) To maintain an approximate steady-state, the bulk of the OVI is recycled back into 10 6 K gas What Matter(s) Around Galaxies, Durham University, June 2017

What Drives the Kinematics? Sloshing, Outflows? Sloshing: coherent bulk motions of halo gas from recent disturbance (e.g. merger, AGN) Possibly similar to that within galaxy cluster cores (e.g. Markevitch & Vikhlinin 2007; ZuHone+2010; Giacintucci et al. 2014) Cold and warm absorbers are co-moving in the hot halo atmosphere, with the observed velocity offsets from the host galaxy due to sloshing of the entire atmosphere What Matter(s) Around Galaxies, Durham University, June 2017

What Drives the Kinematics? Sloshing, Outflows? Sloshing: coherent bulk motions of halo gas from recent disturbance (e.g. merger, AGN) Possibly similar to that within galaxy cluster cores (e.g. Markevitch & Vikhlinin 2007; ZuHone+2010; Giacintucci et al. 2014) 𝐹̇ a@Aa> ≈ energy to recycle OVI to 10 6 K phase; and OVI is largely entrained May generate “cold fronts” and cooling flows emerge naturally; may work in tandem with other sources of feedback to prevent a cooling catastrophe. What Matter(s) Around Galaxies, Durham University, June 2017

The Relationship between OVI and 10 4 K Gas The end state of cooling OVI that is not re-heated to 10 6 K. Cool Cloud Survival times: 10 – 100 Myr (may appear entrained) The low densities suggest that these “clouds” are non-thermally supported 𝑁 ̇ TUV reforms ~10 10 M cold in 30 – 300 Myr Cooling flow model predicts gas at 10 4 K; the exact amount depends on cloud survival time What Matter(s) Around Galaxies, Durham University, June 2017

Takeaways 1. Observations of the CGM indicate a multiphase medium characterized by rich dynamics and complex ionization states. 2. A massive cooling flow ( 10 22 𝑁 ⨀ ) in the CGM is not inconsistent with observations. Out this August! Tumlinson, Peeples, & Werk 2017 ARA&A What Matter(s) Around Galaxies, Durham University, June 2017