transcript
- Slide 1
- TURBULENCE AND HEATING OF MOLECULAR CLOUDS IN THE GALACTIC
CENTER: Natalie Butterfield (UIowa) Cornelia Lang (UIowa) Betsy
Mills (NRAO) Dominic Ludovici (UIowa) Physical Properties of
G0.25+0.01
- Slide 2
- Molecular Clouds in the GC Strong tidal forces from central BH
High temperatures (50- 300K) compared to the disk (10-20K) 1
Densities typically higher Large velocity dispersions 2 Large
turbulence Interaction of the ISM with the strong magnetic field
lines 3 Radio Arc 1 Huttemeister et al. 1993, Mauersberger et al.
1986 2 Bally et al. 1987 3 Morris & Yusef-Zadeh 1989 Brick
Sgr-A* Sgr-B 25 pc
- Slide 3
- Many recent studies on G0.25+0.1 (Brick) Extremely massive and
dense 1 Mass: M Dust ~ 1.3 x 10 5 M Small Radius: ~ 2.8 pc Density:
7.3 x 10 4 cm -3 Young Cloud 2 SiO Shocks Cloud-Cloud Collision
Precursor to Arches-like massive cluster 3 Gas temperature >
dust temperature (~20 K 1 ) cloud-cloud collision Shell like
structure from cloud collision 4 Kauffmann et al. 2013 1 Longmore
et al. (2012) 2 Kauffmann et al. 2013 (SMA/CARMA) 3 Rathborne et
al. (in prep) ALMA 4 Higuchi et al (2014) ALMA
- Slide 4
- Overview Observational Summary Taken January 2012 with the VLA,
DnC array Continuum + Spectral Lines 1.5 km/s spectral resolution
1.5 arcsec resolution Multiple transitions of NH 3 : (1,1)-(9,9) 36
GHz Class I CH 3 OH (4-3) maser 2 bands (K ~25GHz, Ka ~36GHz)
Science Questions What is the velocity structure of the Brick? What
is the gas temperature of the Brick? Do we observe any other
tracers that could tell us about the heating Brick?
- Slide 5
- Distribution of NH 3 in the Brick The cloud is abundant in NH 3
Two curved arc-like structures Brightest emission is in the south
Very good velocity resolution (~1.5km/s) Allows us to do detailed
kinematics Maximum intensity (moment 8) distribution of NH 3
(3,3)
- Slide 6
- Velocity & Velocity Dispersion Complicated structure 2
streams of gas ~10 km/s ~35 km/s Highest velocity dispersions in
the North Average velocity dispersions of ~10 km/s
- Slide 7
- Spectral Analysis Multiple velocity components Resulting in
large velocity dispersions Regions along inner arc have wider
velocity dispersions ~15 km/s
- Slide 8
- NH 3 (3,3) Line Emission starts near the top of the cloud
Smoothly ripples down to the southern part of the cloud
- Slide 9
- Position vs. Velocity Two streamers of gas Higher velocity
cloud and lower velocity cloud converge in the south Position vs.
Velocity diagram of the NH 3 (3,3) line
- Slide 10
- Temperature Temperatures calculated from the (3,3) to (6,6)
line Rotational gas temperature of the cloud is ~95 K Gas
temperature for the Brick is much hotter than clouds in the
Disk
- Slide 11
- Masers ~80 36 GHz Class I Methanol masers 30 have brightness
temperatures > 1000K Majority of the masers are in the South
Traces shocked gas -> cloud- cloud collisions Consistent with
SiO detections
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- Comparison of CH 3 OH Maser to the Velocity and NH 3 The CH 3
OH masers also fall along a similar curve in the velocity structure
and regions with broader lines The 36 GHz CH 3 OH masers trace a
similar structure of the NH 3 Majority of the masers fall along the
brightest NH 3 regions
- Slide 13
- Comparison of CH 3 OH Maser to the Velocity and NH 3 The CH 3
OH masers also fall along a similar curve in the velocity structure
and regions with broader lines The 36 GHz CH 3 OH masers trace a
similar structure of the NH 3 Majority of the masers fall along the
brightest NH 3 regions
- Slide 14
- Is the Ammonia Masing? Betsy Mills
- Slide 15
- Is the Ammonia Masing? Betsy Mills
- Slide 16
- Similar conditions in other GC clouds G0.10-0.08 Bright in NH 3
~50 36 GHz CH 3 OH Masers Similar to the Brick, these also trace
the NH 3 NH 3 (3,3) with CH 3 OH maser contours CH 3 OH maser1.1 mm
(CSO), 20cm (VLA), 8 m (Spitzer) Adam Ginsburg Brick
G0.10-0.08
- Slide 17
- Conclusion What is the velocity structure of the Brick? Very
complex structure with two streams of gas, converging in the south.
What is the gas temperature of the Brick? Rotational gas
temperatures of ~95 K, consistent with other molecular clouds in
the Galactic Center Do we observe any other tracers that could tell
us about the heating Brick? Yes, we detect ~80 CH 3 OH masers Shock
tracer Preliminary analysis suggest that other clouds in the GC
show similar properties. Abundant CH 3 OH masers and NH 3 in
G0.10-0.08 cloud
- Slide 18
- Thank you!
- Slide 19
- HC 3 N Dense cores in both clouds
- Slide 20
- How to use NH 3 to get Temperature What do you do? 1.Convert
from Jy/beam * km/s K * km/s 2.Calculate the corrected column
density 3.Calculate the (rotational) temperature
- Slide 21
- Hyperfine Structure in the (1,1) and (2,2) lines Ratio of
satellite lines to the main line give limits on the optical depth
Optically Thin: large intensity of main peak to satellites
Optically Thick: All lines are about the same intensity Optically
ThinOptically Thick
- Slide 22
- G0.25+0.01 Continuum (25 GHz) What do we see? Weak emission 2
point sources Large diffuse region Tangential filament Several
clumps Several extended features may be resolved out Rms: 0.035
mJy/beam Beam size: 1.87 Largest angular size: 66 1 arcmin1
parsec
- Slide 23
- Do we detect any Methanol Masers? Yes! We see the 36 GHz Maser
Betsy Mills
- Slide 24
- Origin of 36 GHz Methanol Masers? What does the max map tell
us? Majority are in the southern cloud Class I or Class II Shocked
gas from collisions Consistent with Kauffmann et al 2013 Previously
only one H 2 O maser known (Lis et al. 1994)