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?

2 What Matter(s) Around Galaxies, Durham University, June 2017

Part 1: Top 10 Observed Properties of the Low-z CGM

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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

Observation #1: OVI is Ubiquitous Around Star Forming Galaxies

What Matter(s) Around Galaxies, Durham University, June 2017

NFW Dark Matter

NOVI ≈ 1014.5 cm-2 Implies

COS-Halos

Observation #2: Suprathermal Line Widths

What Matter(s) Around Galaxies, Durham University, June 2017

Unresolved, b < 15 km.s

Caveat: possible blending of many narrow components with offsets < 10 km s-1

bth, OVI, 105.5K ≈18 km/s 𝑐#$, 𝑃𝑊𝐽 ≈ 40 − 50 𝑙𝑛 𝑡12 𝑐#$, 𝑇𝑗𝐽𝐽𝐽 < 20 𝑙𝑛 𝑡12 Werk+16

Observation #3: Coincident Line Centroids

What Matter(s) Around Galaxies, Durham University, June 2017

Low Ions: ∆𝑤 ≈ 0 𝑙𝑛 𝑡12 OVI: ∆𝑤 ≈ 5 ± 3 𝑙𝑛 𝑡12

NB: excludes 20% of OVI absorption, i.e. That which occurs without any lowions – aka no-lows

Werk+16

J0401−0540 67_24 −

• 300

300 v (km/s)

− − J1009+0713 204_17 J1009+0713 170_9 J1016+4706 274_6 J1016+4706 359_16 J1112+3539 236_14 − −

• 1. “Narrow” OVI corresponds well with

narrow low-ions (40%)

• 2. “Broad” OVI corresponds well with

narrow low-ions (40%)

• 3. OVI with no low-ion matches within

+/- 50 km/s (20% “No-lows”) Werk+16

Observation #3: Coincident Line Centroids

What Matter(s) Around Galaxies, Durham University, June 2017

Observation #4: Small Kinematic Offsets from Hosts

What Matter(s) Around Galaxies, Durham University, June 2017

∆𝑤 ~50 − 150 𝑙𝑛 𝑡12 no-lows in halos 𝑁>?@A ≲ 102C𝑁⨀

Werk+16

Observation #5: Massive Reservoir of Photoionized ~104 K Gas

What Matter(s) Around Galaxies, Durham University, June 2017

Prochaska et al. 2011: 𝑁E>A$A ≥ 102G 𝑁⨀ Stocke et al. 2013: 𝑁E>A$A ≥ 102G 𝑁⨀ Werk et al. 2014: 𝑁E>A$A ≥ 102G 𝑁⨀ Stern et al. 2016: 𝑁E>A$A ≥ 102G 𝑁⨀ Prochaska et al. 2017: 𝑁E>A$A ≥ 102G 𝑁⨀ Keeney et al. 2017: 𝑁E>A$A ≥ 102G 𝑁⨀ Gripe about the details, but we actually all agree on a very basic level:

Ωm/Ωb = 0.16 ; Mhalo = 1012.2 M⊙ Prochaska+17 Werk+14 NB: Low densities unavoidable 𝑜E>A$A ≲ 101C.J 𝑑𝑛1L

Observation #6: Gas is not Pristine

What Matter(s) Around Galaxies, Durham University, June 2017

Mean L* 𝑎NOP ≈ 0.3 𝑎⨀ 25% of the sample has > 50% of their PDFs > 𝑎⨀! The super solar gas lies at R > 75 kpc

Prochaska+17

Observation #7: Upper limits on NV/OVI Rules

• ut Photoionization of OVI by UVB only

Werk+16

COS-Halos Stacked Data for Star-forming Galaxies Good coverage of NV doublet…yet rarely detected.

Observation #7: Upper limits on NV/OVI Rules

• ut Photoionization of OVI by UVB only

−7 −6 −5 −4 −3 Log nh (cm−3) −2.0 −1.5 −1.0 −0.5 0.0 0.5 Log NNV/NOVI

1 2 4 7 10 6 3 4 1

−2.0 −1.5 −1.0 −0.5 0.0 0.5 −7 −6 −5 −4 −3

−2.0 −1.5 −1.0 −0.5 PIE, HM01

5 4 3 2 1 Log Lmin (kpc)

• Observations require Log U ≪ -1
• Conservative assumptions (i.e., solar

metallicity) give L >> 100 kpc

• For path lengths such as these one

would not expect coherence in velocity structure between OVI and low-ions (i.e. narrow OVI!).

Werk+16

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)

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Observation #8: Low gas densities of 104 K material

0.1 1.0 R/Rvir 101 102 103 104 105 nH/<nH> 10−5 10−4 10−3 nH cm−3

NB: Corrected from Werk+14 by factor of 4 for HM2001; HM2012 roughly consistent with Werk+14

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Observation #9: Red galaxies have HI but infrequently show OVI absorption in CGM

50 100 150 200 ρ [kpc] 12 14 16 18 20 Log NHI [cm−2]

SFR > 0.1 M⊙ yr-1 (blue, star-forming) SFR < 0.05 M⊙ yr-1 (red, quiescent)

−13 −12 −11 −10 −9 −8 Log sSFR [ yr−1] 13.0 13.5 14.0 14.5 15.0 Log NOVI [cm−2]

Quenching appears to modify the abundance of high ions in L* halos while leaving the low ions mostly unaffected (Tumlinson+11)

Observation #10: Uniform OVI velocity dispersion

Nielsen+17; but see Kacprzak+15

The kinematics of OVI absorbers are similar regardless of galaxy color, azimuthal angle, and inclination.

Pixel-velocity two point correlation function using MAGIICAT data

Part 2: One Viable Model Consistent with Top 10 Observed Features of the L* CGM

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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

OVI Represents A Massive Cooling Flow

What Matter(s) Around Galaxies, Durham University, June 2017

McQuinn & Werk 2017

Assume:

• 1. OVI is transitioning through 105.5 K
• 2. 𝑢TUV = 𝑢XAA@ (isobaric cooling time)

→

where

OVI Represents A Massive Cooling Flow

What Matter(s) Around Galaxies, Durham University, June 2017

McQuinn & Werk 2017

Assume:

• 1. OVI is transitioning through 105.5 K
• 2. 𝑢TUV = 𝑢XAA@ (isobaric cooling time)

To generate the observed NOVI requires fluxes into the 105.5 K phase of many tens of solar masses per year.

Higher pressure, higher mass flux. Higher metallicity, lower mass flux

The Behavior of an Isobaric Cooling Flow

What Matter(s) Around Galaxies, Durham University, June 2017

McQuinn & Werk 2017

Model tuned to yield 𝑂TUV ≈ 3 × 102\ 𝑑𝑛1C

≈ The mass participating in these flows must be 1022𝑁⨀, similar to the total baryonic mass for an L* halo.

Implications of the Cooling Flow Model

What Matter(s) Around Galaxies, Durham University, June 2017

To maintain an approximate steady-state, the bulk of the OVI is recycled back into 106 K gas Energetics Thermal pressure bounds

Star formation? 𝐹̇_`# ~ 1049 – 50 erg yr-1 AGN? (flickering? Talk to Ben O.) Cooling within age

• f Universe from

106 K Energetics considerations

What Drives the Kinematics? Sloshing, Outflows?

What Matter(s) Around Galaxies, Durham University, June 2017

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 Drives the Kinematics? Sloshing, Outflows?

What Matter(s) Around Galaxies, Durham University, June 2017

𝐹̇a@Aa> ≈ energy to recycle OVI to 106 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. 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)

The Relationship between OVI and 104 K Gas

What Matter(s) Around Galaxies, Durham University, June 2017

Cool Cloud Survival times: 10 – 100 Myr (may appear entrained) The end state of cooling OVI that is not re-heated to 106 K. Cooling flow model predicts gas at 104K; the exact amount depends on cloud survival time The low densities suggest that these “clouds” are non-thermally supported 𝑁 ̇ TUV reforms ~1010 Mcold in 30 – 300 Myr

Takeaways

What Matter(s) Around Galaxies, Durham University, June 2017

• 1. Observations of the CGM indicate a multiphase medium characterized by

rich dynamics and complex ionization states.

• 2. A massive cooling flow (1022𝑁⨀) in the CGM is not inconsistent with
• bservations.

Out this August! Tumlinson, Peeples, & Werk 2017 ARA&A