The Herschel View
of the
Galactic Center
John Bally1
Hi-GAL PI: Sergio Molinari (Rome)
+ Hi-GAL team … (~150 researchers)
1Center
for Astrophysics and Space Astronomy (CASA)
Department of Astrophysical and Planetary Sciences (APS)
University of Colorado, Boulder
Sgr B2
Sgr B1
8 m 70 m 350 m
G0.25
GCB
50 km/s Sgr A 20 km/s
Outline
• Herschel Hi-GAL: 70, 160, 250, 350, 500 m
• The Central Molecular Zone:
Context
Dust Cold dust, (warm gas); Column density
Star Formation Distribution, Asymmetries, Rate
• Galactic Center Bubble:
Relation to: Sofue-Handa Lobe, Fermi/LAT, …
Nature of 70 m sources
• Star Formation vs. SMBH activity:
Feeding vs. Shielding
Herschel Space Observatory:
(May 2009 - April 2013)
D = 3.5 meter @ L2
PACS: 70, 100, 160 m
SPIRE: 250, 350, 500 m
HIFI:
THz heterodyne
Herschel Galactic Plane Survey
(Hi-GAL)
Herschel Galactic Plane Survey (Hi-GAL)
PI: Sergio Molinari (Rome) + 150 co-Is
~900 hrs
Galactic Plane [360o X 2o] 720 square degree survey
 = 70, 160, 250, 350, 500 m
 = 6 , 11, 15 , 22 , 35 arcsec resolution
Hi-GAL
- inner Galaxy 120o
year 1
Hi-GAL360 - outer Galaxy 120o
year 2
2-GAL
- 60o segments at l = 90o, 270o year 3
Images & Catalogs in preparation
(release in late 2013)
~ 500,000 band-merged compact sources
(YSOs, compact HII regions, post-MS stars, PNe, …)
The CMZ:
Orbits in a Bar
(tri-axial) potential:
x1 vs. x2
Inner Lindblad
Resonance (ILR)
R ~ 450 pc ?
Epicyclic frequency
Bar rotation frequency
~
2:1
Barred Spiral : NGC1097
1 kpc starburst ring
HST
Orbits: x1 - elongated along bar
x2 - elongated orthogonal to bar
V
l
Bally 2010 cartoon
Rodriguez-Fernandez 2006, 2008; model
Molinari et al. (2011) ring
Bania’s Clump 2
l = 1.3
Sgr B2 / B1
Sgr A
Sgr C
24 m
(Hinz 2008; Yusef-Zadeh 2009)
Bania’s Clump 2
l = 1.3
Sgr B2 / B1
70 m
Sgr A
Sgr C
Bania’s Clump 2
l = 1.3
Sgr B2 / B1
Sgr A
160 m
Sgr C
Bania’s Clump 2
l = 1.3
Sgr B2 / B1
Sgr A
250 m
Sgr C
Bania’s Clump 2
l = 1.3
Sgr B2 / B1
Sgr A
350 m
Sgr C
Bania’s Clump 2
l = 1.3
Sgr B2 / B1
Sgr A
500 m
Sgr C
Bania’s Clump 2
l = 1.3
Sgr B2 / B1
Sgr A
Sgr C
1100 m
(Bolocam Galactic Plane Survey
Ginsburg et al. 2012)
Bania’s Clump 2
l = 1.3
Sgr B2 / B1
Sgr A
Sgr C
20 cm
(Yusef-Zadeh 2009)
Bania’s Clump 2
l = 1.3
Sgr B2 / B1
Sgr A
Sgr C
24 m
(Hinz 2008; Yusef-Zadeh 2009)
Bania’s Clump 2
l = 1.3
Sgr B2 / B1
70 m
Sgr A
Sgr C
Central Molecular Zone
24 m, 70 m, 350 m
Central Molecular Zone
24 m, 70 m, 350 m
Central Molecular Zone
20 cm, 70 m, 350 m
Central Molecular Zone
20 cm, 70 m, 350 m
Central Molecular Zone
20 cm, 70 m, 350 m
24 m
350 m
2/3 gas, dust: @ Pos. longitudes
2/3 24 m sources: @ Neg. longitudes
1o => R ~ 150 pc, torbit ~ 8 Myr
Sgr B2
Inert, stable CMZ
Sgr A*
Starburst region
Central Molecular Zone (CMZ)
- x10 - x100 denser, more turbulent than disk GMCs
Traced by HCN, HNCO, CS, SiO, NH3, etc.
V > 20 km/s
- Asymmetry:
Gas & cold dust:
2/3 at POSITIVE longitude, velocity
24 m sources:
2/3 at NEGATIVE longitude
Note: torbit ~ 6 Myr r100 pc V100 km/s-1 (+ 3 to 30 Myr)
Dust T, N(H2) Battersby (2011, A&A, 535, 128) algorithm
T
cold ~ 14 K
warm ~ 50 K
N(H2)
2 x 1021 to
2 x 1024 cm-2
N(H2) from dust
(Rome algorithm)
Sgr A (CNR)
Tdust cold ~ 14 K warm ~ 50 K
(Rome algorithm)
Sgr A (CNR)
The Molinari et al. (2011) ~100 pc ring
Sgr A (CNR)
The Molinari et al. (2011) R ~100 pc ring
Region of Starburst activity in CMZ
But … Sgr B2 Proper Motion ~ 80 km/s
=> R ~ 150 to 200 pc?
Galactic Center: 8 m
Sgr B2
Sgr A (CNR)
Galactic Center Bubble: 24 m
Sgr A (CNR)
Sgr A (CNR)
8 m 70 m 350 m
Galactic Center: 20 cm
Sgr A (CNR)
Galactic Center Bubble
- Brightest super-bubble in Galaxy at 24 m
- D ~ 30 pc
- Arches, Pistol clusters, Sgr A East SNR
A nested set of Bubbles?
Sgr A East:
GCB:
1 pc
30 pc
Sofue-Handa (84) lobe: 150 pc
Fermi-LAT bubble:
5,000 pc
A weak `nuclear super-wind’ ?
Star-formation -or- SMBH ?
Galactic Center Bubble => Sofue-Handa Lobe
=> Fermi-LAT Bubble ?
Finkbeiner et al. (2010)
SofueHanda
Lobe
3.5 cm
(GBT)
2 deg.
Law et al. (2009, 2010)
Caution:
Sco-Cen superbubble
150 pc from Sun
Sgr B2
Continuum
CO SED
(Etxaluze+ 2013)
Sgr C (G359.44-.10)
3.6, 4.5, 8 m
Kendrew et al. poster
280 GHz continuum
2.12 m H2
Bania’s Clump 2
l = 3.2o
106 Mo
Most CMZ
molecular gas
at positive
Longitudes,
& positive
Velocities
Dense Gas with little / no star formation
Bania’s Clump 2 (l = 3.2o) & l = 1.3o - 1.5o
- Little 8, 24, 70 m emission
- Little or no star-formation
- Strong thermal SiO => shocks?
Location:
At end of innermost x1 orbit ?
Along length of x1 orbit ?
Where x1 and x2 intersect ?
Bania’s Clump 2
24 um, 70 um, 350 um
G0.253+0.016 (the “Brick” or “Lima Bean”)
105 Mo 3 pc, dense cloud in CMZ
VERY LITTLE STAR FORMATION !
(the most extreme IRDC in the Galaxy?)
3.6 - 8.0 m (Spitzer)
70 m (Hi-GAL)
450 m (SCUBA)
(Longmore et al. 2012) - ALMA Cycle 0 data (Rathborne et al. 2013)
HCO+ J = 1-0
21 km/s
18 km/s
14 km/s
ALMA Cycle 0 data
Rathborne et al. 2013
Bally et al. 2013
HCO+ J = 1-0
28 km/s
24 km/s
21 km/s
ALMA Cycle 0 data
Rathborne et al. 2013
Bally et al. 2013
HCO+ J = 1-0
34 km/s
31 km/s
28 km/s
ALMA Cycle 0 data
Rathborne et al. 2013
Bally et al. 2013
HCO+ J = 1-0
41 km/s
38 km/s
34 km/s
ALMA Cycle 0 data
Rathborne et al. 2013
Bally et al. 2013
HCO+ J = 1-0
48 km/s
44 km/s
41 km/s
ALMA Cycle 0 data
Rathborne et al. 2013
Bally et al. 2013
HCO+ J = 1-0
55 km/s
51 km/s
48 km/s
ALMA Cycle 0 data
Rathborne et al. 2013
Bally et al. 2013
HCO+ J = 1-0
62 km/s
58 km/s
55 km/s
ALMA Cycle 0 data
Rathborne et al. 2013
Bally et al. 2013
Sgr A & Circum Nuclear Ring (CNR):
70 um, 160 um, 350 um (SHARC/CSO)
Black Hole
HCN (1-0) + P
50 km/s cloud
20 km/s cloud
Feeding star formation in the CNR?
Sgr A cluster
L-band: (Viehmann 06)
Hot (400 K), dense molecular gas CO in 3 pc ring
Sgr A PACS/SPIRE spectrum (Goicoechea+ 2013)
HF & para H2O in CMZ
CNR HIFI (Herschel)
(Sonnentrucker+ 2013)
50 km/s cloud
20 km/s cloud
Hot (400 K) CO in 3 pc ring
CNR HIFI (Herschel)/GREAT (SOFIA)
(Requena-Torres+ 2013)
Future
- ALMA
small-scale line / continuum / polarization
- SOFIA
HAWC++ MIR continuum / polarization / narrow-band
GREAT CII, NII, OI, OIII, etc.
FORCAST 11 - 37 um continuum
- JVLA
NH3, SiO, CS, H2CO / high-f continuum / RRLs
- CCAT
large-scale CI, CO 4-3 / continuum
- JWST
small-scale 2 - 28 um
Summary
• ~ 90 - 150 pc ring of cold dust and gas
•
•
•
•
Contains Sgr B2, Sgr B1, Brick, Sgr C
Most extreme star formation at r < 100 pc
Large V features: l = 1.3o, Bania’s Clump 2 (l = 3.2o),
No (or little) star formation:
Galactic Center Bubble: 70 m: YSOs or externally heated?
Multiple SN, massive star winds, ionization
Feeds Sofue-Handa Lobe (~1 deg.) ?
Fermi-LAT Bubble (> 20 deg.) ?
Star Formation in the CMZ:
“Mini-starbursts” in Sgr B2
Asymmetry: Gas-dust at Positive longitude/velocity
24 m sources at Negative longitude
24 m sources: MYSOs, MS-stars
- or - externally illuminated OH/IR, RSG, PNe, …
<SFR>
0.007 - 0.1 Mo/yr ? Variable?