Discovery of Massive Young Stellar Objects in the Galactic Center with Warm CO2 Gas Absorption

Deokkeun An (IPAC/Caltech)

Solange Ramirez (IPAC/Caltech)

Kris Sellgren (Ohio State U.)

et al., 2009, ApJL, submitted

Galactic Center: Central Molecular Zone = central ~200 pc

Star formation conditions unique because tidal shear, high gas pressure

Evidence for recent star formation:

Compact H II regions

Young star clusters (1—8 Myr old)

Search for candidate Young Stellar Objects (YSOs) with Spitzer IR images + Spitzer IR spectra

Sgr B2

Sgr C

Sgr B1

Quintuplet Cluster

Central Cluster

+ Sgr A*

Arches Cluster

280 pc

280 pc

Imag

e C

ou

rtes

y: N

AS

A /

JPL

-Cal

tech

SSTGC 797384

Warm molecular gas in massive YSO in the Galactic Center

DeokkeunAn, Ramirez, Sellgren, et al. ApJL, submitted

Warm C2H2 HCN CO2 gas

(absence of [Ne III] gas)

Fitting CO2 ice profiles in GC YSOs with lab spectra

“Shoulder” seen in CH3OH-rich ices

Gas-Phase Absorption from C2H2, HCN, CO2

GC YSO model fits:T = 100—400 KX(HCN) = 2—70 x10-7

Sgr B2: T = 100—200 K X(HCN) = 0.2—0.7 x10-7

Conclusions:Spectra of GC YSO candidates show warm CO2, HCN, C2H2 gas in absorption

Spectra also show solid-phase CO2, H2O, silicate dust

CO2 ice profile suggestive of high CH3OH ice abundance

Molecular abundances comparable to other massive YSOs, much larger than towards Sgr B2 or TMC-1

Collaborators:Adwin Boogert (Caltech)

Richard Arendt (NASA/Goddard)

Angela Cotera (SETI Institute)

Thomas Robitaille (St. Andrews U.)

Mathias Schultheis (Besancon Obs.)

Howard Smith (CFA)

Susan Stolovy (SSC/Caltech)

+ = SSTGC 797384

+ = SSTGC 803187

Sgr B2 3.6 cm continuum Mehringer et al 1993

Sgr B2 (N)

Sgr B2(M)

X = SSTGC 524665

Box = H2O maser

+ = OH maser

3 cm continuum

Forster & Caswell (2000)

+ = SSTGC 797384

+ = SSTGC 803187

Sgr B2 CH3OH Jones et al 2008

S

M

N

+ = SSTGC 797384

+ = SST 803187

Sgr B2 1.3 cm continuum Gaume et al 1995

Sgr B2(M)

Sgr B2 (N)