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

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

Jan 05, 2023 450 likes •785 views

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 didnt we see anything spectacular from G2? What is G2?

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SLIDE 1

G2 and Sgr A*: A cosmic fizzle at the Galactic Center

Brian Morsony

University of Maryland Collaborators: Jared Workman, Brandon Gracey, DooSoo Yoon

1

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SLIDE 2

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

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SLIDE 3

Simulations Setups

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  • 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
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SLIDE 4

4 Cloud Profiles

4

2.0×1015 4.0×1015 6.0×1015 8.0×1015 1.0×1016 1.2×1016 Radius (cm) 100 102 104 106 108 Density/mH (cm−3) norm ext flat rsq

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SLIDE 5

Norm Density

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SLIDE 6

Why didn’t we see anything spectacular?

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  • Accretion rates
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SLIDE 7

Sgr A* accretion rate - Norm

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−4 −2 2 4 Time relative to periapsis (years) 1015 1016 1017 1018 1019 Accretion rate (g/s) cloud total

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SLIDE 8

Sgr A* accretion rate

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  • Total

−4 −2 2 4 Time relative to periapsis (years) 1015 1016 1017 1018 1019 Accretion rate (g/s) norm extended flat rsq −4 −2 2 4 Time relative to periapsis (years) 1015 1016 1017 1018 1019 Accretion rate (g/s) no cloud rsq flat extended norm

Total Cloud only

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SLIDE 9

Sgr A* cumulative accretion

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  • Total

Total Cloud only

−4 −2 2 4 Time relative to periapsis (years) 2•1025 4•1025 6•1025 8•1025 1•1026 Total accretion (g) norm extended flat rsq no cloud −4 −2 2 4 Time relative to periapsis (years) 2•1025 4•1025 6•1025 8•1025 1•1026 Total accretion (g) norm extended flat rsq no cloud

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SLIDE 10

Why didn’t we see anything spectacular?

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  • 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

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SLIDE 11

What is G2?

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  • Model emission from our simulations
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SLIDE 12

Cloud Br-Gamma

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−4 −2 2 4 Time relative to periapsis (years) 1026 1027 1028 1029 1030 1031 Br−gamma emission (erg/s) rsq flat extended norm

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SLIDE 13

Norm Br-Gamma

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<< Nozzle Shock

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SLIDE 14

R2 Br-Gamma

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<< Nozzle Shock

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SLIDE 15

Br-Gamma Size

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−4 −2 2 4 Time relative to periapsis (years) 20 40 60 80 100 Spatial FWHM (mas) norm extended flat rsq

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SLIDE 16

Br-Gamma Size

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−4 −2 2 4 Time relative to periapsis (years) 20 40 60 80 100 Spatial FWHM (mas) norm extended flat rsq

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SLIDE 17

Cloud Br-Gamma vs. Data

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−4 −2 2 4 Time relative to periapsis (years) 5.0×1030 1.0×1031 1.5×1031 2.0×1031 2.5×1031 Br−gamma emission (erg/s) norm extended flat rsq Gillessen et al. 2013 Phifer et al. 2013 Pfuhl et al. 2015 Valencia−S. et al. 2015

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SLIDE 18

Br-Gamma Velocity vs. Data

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−4 −2 2 4 Time relative to periapsis (years) −3000 −2000 −1000 1000 2000 3000 Velocity (km/s) Kepler rsq flat extended norm

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SLIDE 19

Br-Gamma FWHM vs. Data

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

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SLIDE 20

Cloud Bolometric vs. Data

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−4 −2 2 4 Time relative to periapsis (years) 1033 1034 1035 1036 Bolometric luminosity (erg/s) norm extended flat rsq Witzel et al. 2015

+

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SLIDE 21

Cloud Bolometric vs. Data

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−4 −2 2 4 Time relative to periapsis (years) 1033 1034 1035 1036 Bolometric luminosity (erg/s) norm extended flat rsq Witzel et al. 2015

+

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SLIDE 22

Cloud X-ray vs. Data

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−2 −1 1 2 Time relative to periapsis (years) 1×1033 2×1033 3×1033 4×1033 Cloud X−ray luminosity (erg/s) norm extended flat rsq Haggard et al. 2014

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SLIDE 23

What is G2?

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  • 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
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SLIDE 24

Conclusions

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  • 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

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SLIDE 25

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SLIDE 26

Norm Br-Gamma

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<< Nozzle Shock

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SLIDE 27

Norm Temperature

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SLIDE 28

R2 Density

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SLIDE 29

R2 Temperature

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SLIDE 30

Sgr A* accretion rate

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  • a

−4 −2 2 4 Time relative to periapsis (years) 1015 1016 1017 1018 1019 Accretion rate (g/s) no cloud rsq flat extended norm −4 −2 2 4 Time relative to periapsis (years) 1015 1016 1017 1018 1019 Accretion rate (g/s) norm extended flat rsq

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SLIDE 31

Sgr A* accretion rate

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−4 −2 2 4 Time relative to periapsis (years) 1015 1016 1017 1018 1019 Accretion rate (g/s) nw wind