# Presentation: 037889

## Gas Dynamics in the Circum-Black-Hole Environment in the Galactic Center

- Gabriel Rockefeller
- Los Alamos National Laboratory
- The University of Arizona

## Components of the Galactic center

- Sgr A
- Sgr A*

- Image courtesy of NRAO/AUI and N.E. Kassim, Naval Research Laboratory

**Notes:**
Wide-field view of the Galactic center.  SNR 359.1-0.5 is a nice remnant.  We can’t even see Sgr A East yet.
First proposed as a SMBH by Lynden-Bell & Rees (1971), observed using NRAO interferometer at Green Bank (1974), confirmed 1975.  Named in 1982 to distinguish it (Sgr A*) from the rest of the Sgr A complex.
Sgr A complex, Sgr B2.

## Components of the Galactic center

*Chandra*: 0.5–7 keV log-scaled colors
- Sgr A West
- Sgr A East

- Baganoff et al. 2003

**Notes:**
An 8’.4 by 8’.4 (20pc x 20pc) Chandra view of the GC, zoomed in quite a bit from the VLA image.  Sgr A West (ionized dust spiral lit by central stars).  Sgr A East is on the other side (switch to radio image).

## Components of the Galactic center

- 20 cm radio emission from Sgr A East

- NASA/G.Garmire (PSU)/F.Baganoff (MIT)/Yusef-Zadeh (NWU)

## Components of the Galactic center

- 0.5–7 keV log-scaled colors, plus 6 cm radio contours
- 2–10 keV: 7.6e31 erg/s/arcsec2
- kT = 1.3 keV

- Baganoff et al. 2003

**Notes:**
VLA 6cm Sgr A*/Sgr A West radio contours overlaid on 1’.3 by 1’.5 (3.1pc x 3.6pc) Chandra image.  Red dot at center is Sgr A*.  Western arc is ionized inner edge of CND; X-ray-emitting plasma may be confined by CND on western side.
Fit a model for an absorbed optically thin thermal plasma (Raymond-Smith): 7.6e31 erg/s/arcsec^2, 1.3keV; oop, may not be in ionization equilibrium (iron line emission)

## Components of the Galactic center

- Christopher et al. (2005)

## A cartoon view of the GC

- Herrnstein & Ho (2004)

**Notes:**
Finally, a cartoon overview of the components I’ve been talking about.  Notice the illuminated western arm of the minispiral.

## Conclusions

- The central few parsecs of the Galaxy are filled with the winds of massive stars
- Sgr A East is only ~1700 years old
- The explosion that produced Sgr A East did not significantly change the mass or angular momentum of the gas within 0.1 pc of Sgr A*

## Massive stars in the central parsec

- Tanner et al. (2005)

**Notes:**
Identified massive Wolf-Rayet and O/B-type stars with high-velocity winds that eject a total of 3e-3 solar masses per year into the GC environment.  We use these stars as our initial conditions in our simulations and allow them to inject matter into the volume of solution.  Br-alpha emission originally established average outflow speed, which combined with estimates of n to give mdot in the range of 4e-3 solar masses per year.

## Stellar wind material fills the central parsecs of the GC

- Temperature isosurfaces: 104 K (blue) and 107 K (red)

**Notes:**
Box is  a 1pc by 1pc by 1pc cube.  Blue surfaces indicate gas with temperatures of 1e4 K (basically just the temperature of the initial winds); red surfaces indicate temperatures of 1.5e7 K (shocked gas between stars).

## Stellar wind material fills the central parsecs of the GC

- Simulated 2–10 keV luminosity matches Chandra luminosity

**Notes:**
One very important caveat that I want to get out of the way right now: the inner boundary for our calculation is at r = 0.06 pc, or 1.5’’.  Capture radius for a 2.6e6 solar mass black hole is somewhere between 6.9e16 cm (1000 km/s winds) and 2.5e17 cm (500 km/s winds)_x0001__x0001_, so we’re sort of marginally resolving it.

## Conclusions

- The central few parsecs of the Galaxy are filled with the winds of massive stars

**Notes:**
Mention Jorge’s simulations.

## The Impact of Sgr A East

- Chandra observes a ridge toward Sgr A East:3.0e33 erg/s (2–10 keV)

## The Impact of Sgr A East

- Grayscale: 1e29 erg/s/pixel–1e32 erg/s/pixel
- Contours: 1e30 erg/s/pixel (green), 1e31 erg/s/pixel (blue)

## The Impact of Sgr A East

- 2–10 keV X-ray luminosity from simulated and observed arc

**Notes:**
Ignore the very faint line for a second, and remember that 3e33 erg/s is the number we’re trying to match.  Where does the solid line reach 3e33 erg/s?  1700 years.  Hallelujah.  That’s the support for conclusion #2, that Sgr A East is much younger than previously believed.

## The Impact of Sgr A East

- Grayscale: 1e29 erg/s/pixel–1e32 erg/s/pixel
- Contours: 1e30 erg/s/pixel (green), 1e31 erg/s/pixel (blue)

## Conclusions

- The central few parsecs of the Galaxy are filled with the winds of massive stars
- Sgr A East is only ~1700 years old

**Notes:**
So that’s an age estimate.  On to the effect of the explosion on Sgr A*.

## Sgr A East has little effect on gas profile near Sgr A*

- Neither the amount nor the angular momentum of captured gas are significantly affected

## Simulations of stars on “realistic” trajectories

- Accretion rate is mostly constant, and much smaller than in our simulation

- Cuadra et al. 2005

**Notes:**
Before we move on, I should add to that comment about our inner boundary.  Cuadra et al. did simulations with a smaller inner boundary (0.1’’) and find, as expected a smaller accretion rate.  I’ll talk about spikes in a minute.

## Conclusions

- The central few parsecs of the Galaxy are filled with the winds of massive stars
- Sgr A East is only ~1700 years old
- The explosion that produced Sgr A East did not significantly change the mass or angular momentum of the gas within 0.1 pc of Sgr A*