Observing the Galactic Center with SOFIA

Mark Morris, UCLA

SOFIA is the successor to the Kuiper Airborne Observatory, a C141A transport stationed at NASA/Ames 1971 – 1995.

SOFIA’s telescope has 7.5 times the collecting area of the KAO telescope, a conventional Cassegrainreflector with a 36-inch mirror.

The CircumNuclear Disk (the CND), discovered with the KAO (Becklin, Gatley & Werner 1982)

J. Davidson et al 1992 (using KAO) 90 µm

H2

Yusef-Zadeh et al

(HST)

The clumpy disk is heated approximately equally by central stellar cluster of old stars and by the UV flux from the bright young stars in the central cluster. Total UV flux implied: ~107 L.

A few KAO highlights, to make the case for airborne astronomy:

63 µm OI emission measured with the KAO: Jackson et al. 1993FWHM: 22”

OI emission peaks in the interior of theCND, so the ionized gas there is mixed with atomic gas, presumably producedby photodissociation.

An indication that there is far more gasinside the CND (300 M8) than the ionized gas in Sgr A West (30 M8)

Latvakoski, H. M.; Stacey, G. J.; Gull, G. E.; Hayward, T. L. 1999

KWIC on the KAO

31.5 µm 37.7 µm

Hot dust in the Arched Filaments, ionized & heated by the Arches Cluster

2003

50 and 100 µm polarimetry from theKAO, and 350 µm polarimetry using theHertz polarimeter on the CSO

Dotson et al. 2000 and

Far-IR polarimetry !

Stratospheric Observatory for Infrared Astronomy: SOFIA

• This long-promised replacement for the KAO

will carry the torch for the next 20 years.• A Boeing 747SP aircraft modified to

accommodate a 2.5-meter diameter reflecting telescope <> compare to Herschel – 3.5 m

• SOFIA is a joint NASA + DLR sub-orbital observatory– 80% NASA – 20% DLR -- Germany’s Aerospace Agency

KAO experience Airborne astronomy is exceptionally well suited for study of the Galactic center

USRA (Universities Space Research Association) will manage the science operations of SOFIA - science center: NASA/Ames Research Center - the German SOFIA science center is in Stuttgart

NASA’s Dryden Flight Research Center will operate the aircraft

Operating altitude: 37,000 – 45,000 ft.

Advantages of SOFIA:

Long duration, once it starts

Portable observatory

Flexibility of operation, and instrument swapping

Real-time observer participation

High spectral resolution

High spatial resolution in mid to far IR, compared to any other existing platform.

Disadvantages: timing, with respect to Herschel cost of jet fuel

Telescope in Aircraft

Looking aft toward the pressure bulkhead & telescope assembly

Observatory Layout

FORCASTFaint Object Infrared Camera for the SOFIA TelescopeA mid-IR camera, 256 x 256 pixels, operating at 5-40 µm

First Science Instruments:

GREAT German Receiver for Astronomy at Terahertz FrequenciesA heterodyne spectrometer operating at 60-200 µm

other 1st generation instruments:HAWC High-resolution Airborne Wideband CameraEXES Echelon-Cross-Echelle SpectrographFIFI-LS Field Imaging Far-Infrared Line SpectrometerCASIMIR Caltech Submm Interstellar Medium Investigations ReceiverFLITECAM First Light Infrared Test Experiment CameraSAFIRE Submillimeter and Far-Infrared ExperimentHIPO High-speed Imaging Photometer for Occultations

SOFIA spectroscopy.

EXES: [S III] 18.7 µm, [S I] 25.2 um, [O IV] 25.9 µm; H2 @ 17 & 28 µm R~20,000 (15 km/s)

FIFI LS: [O III] 52, 88 µm, [O I] 63 µm, R~3000 (100 km/s) [O I] 145 µm, [C II] 158 µm, CO J=14-13, 17-16, 22-21, 27-26 R~2000

GREAT: [OI] 63 um; R~20,000 (15 km/s)

CASIMIR: CO 8-7, 9-8, 10-9, 12-11, HCN 6-5, 8-7, 9-8, 12-11, 13-12, HCN 14-13, 16-15, HCO+ 11-10

The Galactic Center from Spitzer

Galactic center issues that SOFIA can address:

I. Thermal balance of GC clouds – what is the dominant heating source?

Candidates: shocks, X-rays, dissipation of hydromagnetic waves

Shock heating – investigate with the 63 and 149 µm fine structure lines of OI, produced in both shocks and PDRs.<> But compare to [CII] 158 µm line, which is much less affected by shocks.

<> Use the intensity ratio of the two [OI] lines to control for density

II. Heat flow through the GC ISM – dust and gas luminosities

III. Magnetic field measurements <> equip the HAWC far-IR imager with a polarimeter to

measure alignment direction of dust grains using the polarization vector of their thermal emission.

IV. Chemistry – into the THz regime

SOFIA Schedule• First open door flight: November

2009• First Science: August 2010• Full operations: 2014• 160 flights per year, 8-hr flights• Operation for 20 years

Let’s go……

START, TAXI, TAKEOFF GW 570.03000 LBS TAXI FUEL

TOTAL FUEL USED = 169,000 LBS. (24,708 Gallons)

TOTAL CRUISE TIME = 7.05 HRS.TOTAL FLIGHT TIME = 8.05 HRS

ASSUMPTIONSZFW 381,000 LBS.ENGINES OPERATE AT 95% MAX CONT THRUST AT CRUISE25,000 LBS. FUEL TO FIRST LEVEL OFFCLIMB TO FIRST LEVEL-OFF AT MAX CRUISE WTLANDING WITH 20,000 LBS. FUELBASED ON NASA AMI REPORT: AMI 0423 IRBASED ON 747 SP FLIGHT MANUAL TABULATED DATASTANDARD DAY PLUS 10 DEGREES CCRUISE SPEED-MACH .84

CRUISE84,000 LBS. FUEL

F.F. 20,200 LBS/HR.

CRUISE52,000 LBS.FUEL

F.F. 17,920 LBS/HR.

FL410, 4.2 HrGW 542.0

FL430, 2.9 HrGW 458.0

DESCENTGW 406.05,000 LBS. FUEL.5 HRS.

LANDINGGW 401.0 20,000 LBSFUEL

CLIMB25,000 LBS. FUEL.5 HRS.

Flight Profile 1 Performance with P&W JT9D-7J Engines: Observations - start FL410, duration 7.1 Hr

START,TAXI,TAKEOFFGW 638.03000 LBS TAXI FUEL

TOTAL FUEL USED = 237,000 LBS. (34,650 Gallons)

TOTAL CRUISE TIME = 10.15 HRS.TOTAL FLIGHT TIME = 11.15 HRS.

CRUISE68,000 LBS. FUEL

F.F. 21,930 LBS/HR.

CRUISE84,000 LBS. FUEL

F.F. 20,200 LBS/HR.

CRUISE52,000 LBS.FUEL

F.F. 17,920 LBS/HR.

FL390, 3.1 HrGW 610.0

FL410, 4.2 HrGW 542.0

FL430, 2.9 HrGW 458.0

DESCENTGW 406.05,000 LBS. FUEL.5 HRS.

LANDINGGW 401.020,000 LBSFUEL

CLIMB25,000 LBS. FUEL.5 HRS.

Performance with P&W JT9D-7J Engines: Observations - start FL390, duration 10.2 Hr

ASSUMPTIONSZFW 381,000 LBS.ENGINES OPERATE AT 95% MAX CONT THRUST AT CRUISE25,000 LBS. FUEL TO FIRST LEVEL OFFCLIMB TO FIRST LEVEL-OFF AT MAX CRUISE WTLANDING WITH 20,000 LBS. FUELBASED ON NASA AMI REPORT: AMI 0423 IRBASED ON 747 SP FLIGHT MANUAL TABULATED DATASTANDARD DAY PLUS 10 DEGREES CCRUISE SPEED-MACH .84

Flight Profile 2