G2 and Sgr A*: A cosmic fizzle at the Galactic Center Brian Morsony - PowerPoint PPT Presentation

G2 and Sgr A*: A cosmic fizzle at the Galactic Center Brian Morsony University of Maryland Collaborators: Jared Workman, Brandon Gracey, DooSoo Yoon 1

Questions • Why didn’t we see anything spectacular from G2? • What is G2? • Simulate different cloud structures • Morsony et al. submitted, arXiv:1508.00384 2

Simulations Setups • Start with a cloud 5 years before periapsis • Orbit from Gillessen et al. 2013 • Gravity from Sgr A* only • Background co-moving with cloud • Include cooling • Resolution of 1.2e14 cm ~ 1 mas ~ 8 AU • Accretion radius of 1 pixel 3

4 Cloud Profiles 10 8 norm ext flat rsq 10 6 Density/m H (cm − 3 ) 10 4 10 2 10 0 2.0 × 10 15 4.0 × 10 15 6.0 × 10 15 8.0 × 10 15 1.0 × 10 16 1.2 × 10 16 0 Radius (cm) 4

Norm Density 5

Why didn’t we see anything spectacular? • Accretion rates 6

Sgr A* accretion rate - Norm 10 19 10 18 Accretion rate (g/s) 10 17 10 16 total cloud 10 15 − 4 − 2 0 2 4 Time relative to periapsis (years) 7

Sgr A* accretion rate 10 19 10 19 norm extended flat rsq 10 18 10 18 Accretion rate (g/s) Accretion rate (g/s) 10 17 10 17 norm 10 16 extended 10 16 flat rsq no cloud • Total 10 15 10 15 − 4 − 2 0 2 4 − 4 − 2 0 2 4 Time relative to periapsis (years) Time relative to periapsis (years) Total Cloud only 8

Sgr A* cumulative accretion 1•10 26 1•10 26 norm norm extended extended flat flat 8•10 25 8•10 25 rsq rsq no cloud no cloud Total accretion (g) Total accretion (g) 6•10 25 6•10 25 4•10 25 4•10 25 2•10 25 2•10 25 • Total 0 0 − 4 − 2 0 2 4 − 4 − 2 0 2 4 Time relative to periapsis (years) Time relative to periapsis (years) Total Cloud only 9

Why didn’t we see anything spectacular? • Not much change in accretion rate • True for different background density/ velocity, accretion radius, cooling • Cloud accounts for ~ 20% of material accreted after periapsis • More extended cloud leads to more accretion, but still a small change overall 10

What is G2? • Model emission from our simulations 11

Cloud Br-Gamma 10 31 Br − gamma emission (erg/s) 10 30 10 29 10 28 norm 10 27 extended flat rsq 10 26 − 4 − 2 0 2 4 Time relative to periapsis (years) 12

Norm Br-Gamma << Nozzle Shock 13

R2 Br-Gamma << Nozzle Shock 14

Br-Gamma Size 100 norm extended flat 80 rsq Spatial FWHM (mas) 60 40 20 0 − 4 − 2 0 2 4 Time relative to periapsis (years) 15

Br-Gamma Size 100 norm extended flat 80 rsq Spatial FWHM (mas) 60 40 20 0 − 4 − 2 0 2 4 Time relative to periapsis (years) 16

Cloud Br-Gamma vs. Data 2.5 × 10 31 norm Gillessen et al. 2013 extended Phifer et al. 2013 flat Pfuhl et al. 2015 2.0 × 10 31 Br − gamma emission (erg/s) rsq Valencia − S. et al. 2015 1.5 × 10 31 1.0 × 10 31 5.0 × 10 30 0 − 4 − 2 0 2 4 Time relative to periapsis (years) 17

Br-Gamma Velocity vs. Data 3000 2000 1000 Velocity (km/s) 0 − 1000 norm extended − 2000 flat rsq Kepler − 3000 − 4 − 2 0 2 4 Time relative to periapsis (years) 18

Br-Gamma FWHM vs. Data 3000 norm Gillessen+ 2013 extended Phifer+ 2013 2500 flat Pfuhl+ 2015 rsq Valencia − S.+ 2015 FWHM Velocity (km/s) 2000 1500 1000 500 0 − 4 − 2 0 2 4 Time relative to periapsis (years) 19

Cloud Bolometric vs. Data 10 36 norm Witzel et al. 2015 extended flat Bolometric luminosity (erg/s) rsq + 10 35 10 34 10 33 − 4 − 2 0 2 4 Time relative to periapsis (years) 20

Cloud Bolometric vs. Data 10 36 norm Witzel et al. 2015 extended flat Bolometric luminosity (erg/s) rsq + 10 35 10 34 10 33 − 4 − 2 0 2 4 Time relative to periapsis (years) 21

Cloud X-ray vs. Data 4 × 10 33 norm Haggard et al. 2014 extended flat Cloud X − ray luminosity (erg/s) rsq 3 × 10 33 2 × 10 33 1 × 10 33 0 − 2 − 1 0 1 2 Time relative to periapsis (years) 22

What is G2? • Can’t explain all observations with one simple model • Need extended gas for Br-gamma FWHM increase, spatial extent • Need compact source for narrow post- periapsis emission, constant L’ band luminosity • Can be dense core, DSO, star 23

Conclusions • Why didn’t we see anything spectacular? – Cloud is not massive enough, doesn’t get close enough to significantly change accretion • What is G2? – Seems to need an extended gas component and a compact component 24

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Norm Br-Gamma << Nozzle Shock 26

Norm Temperature 27

R2 Density 28

R2 Temperature 29

Sgr A* accretion rate 10 19 10 19 norm extended flat • a rsq 10 18 10 18 Accretion rate (g/s) Accretion rate (g/s) 10 17 10 17 norm 10 16 10 16 extended flat rsq no cloud 10 15 10 15 − 4 − 4 − 2 − 2 0 0 2 2 4 4 Time relative to periapsis (years) Time relative to periapsis (years) 30

Sgr A* accretion rate 10 19 10 18 Accretion rate (g/s) 10 17 10 16 wind nw 10 15 − 4 − 2 0 2 4 Time relative to periapsis (years) 31