Chemical Differentiation in Sagittarius B 2( N ): First High Resolution Results Joanna F . Corby1; Anthony J . Remijan2,1; Maria Cunningham3; Paul Jones3 1 University of Virginia , Department of Astronomy , Charlottesville , VA ; 2 National Radio Astronomy Observatory , Charlottesville , VA ;

3 University of New South Wales , Astrophysics , Sydney NSW

Sagittarius B2: The High Mass Star Sagittarius B2(N)

Forming Region in the Galactic Center Physically complex – compact and extended HII regions on size scales smaller than the beam of a single dish radio telescope – expanding ionization fronts (i.e. K4, K5, and K6) – warm dense molecular material in the Large Molecule Heimat (LMH) hot core – embedded in extended quiescent molecular material, the Sgr B2 envelope Continuum emission map at 3.5cm generated with the Robert C. Byrd Green Bank Telescope shows VLA continuum image of Sgr B2(N) at 18 GHz. The K1 - Chemically diverse 2 the position of Sgr B2 within the central 200pc of the Galactic Center. (Figure adapted from Law et K4 continuum cores, K5 and K6 shells , methanol maser – host to the most complex 3 4 al. 20031.) source “h” , and the Large Molecule Heimat (LMH) are chemistry observed in the ISM labeled.

Figure 4 (above): An initially unidentified transition in both the PRIMOS spectrum (blue) and the laboratory spectrum (black), Sgr with a single dish from the GBT PRIMOS: motivatedFigure 6 (below):work that Continuum led to the detectionimage of ofSgr a PRIMOS9, a 1-50GHz GBT survey of Sgr B2(N) shows newB2(N) interstellarat 18 GHz, overlayed molecule with and integrated refined emission line contours of HC N, CH CN,7 – Nitriles are almost exclusively in absorption measurements of the spectrum of3 HNCHCN3 . CH2CHCN, CH3CH2CN, and CH2CN. – Highly subthermal (3K < Tex< 8K) Dashed line contours are in absorption. Suggests: Nitriles ≠ Hot Core Species

Sgr through broadband interferometers: · VLA observations targeting multiple transitions of nitriles at 18 – 21 GHz with ~1 arcsecond resolution. · ATCA spectral line survey of Sgr B2(N) from 30 – 50 GHz with 5 to 12 arcsecond resolution. Figure 2: Sgr B2 continuum at 18GHz from VLA data with a ~.8 x .5 arcsecond beam shows physical structure on spatial scales much smaller than a single dish beam. The Green Bank Telescope's FWHM beam at 18GHz is represented by the green circle, centered on the LMH.

Hot Cores Not Hot Cores

– In an ATCA survey of Sgr – We've identified ~95% of the spectral lines detected towards the K4 compact B2(N) from 30 - 50 GHz, we continuum core and the K5 – K6 shells. Diverse oxygenated molecules, nitriles detect ~1000 spectral lines (with a CΞN functional group), and imines (with a C=N-H functional group) are towards the LMH, the famous observed. hot core in Sgr B2. – We detect recombination lines and the lines from the following molecules – The spectrum of the methanol (blue species were not detected towards K4) + maser source “h”, on the NW Small molecules: CS, HCS, HCS , H2CS CCS, SiO, NH3, H2CO, c-C3H2, l-C3H, HSCN

edge of the K5 shell is closer to Oxygenated species: NH2CHO, CH3CHO, CH3OCHO, CH3OCH3, t-HCOOH, H2CCO the LMH than it is to K4-K6. It is Nitriles: HC N, HC N, CH CN, CH CHCN, characterized by emission lines between high energy states (>50 K), and may 3 5 3 2 CH CH CN, ∙CH CN be Sgr B2(N)'s second hot core. 3 2 2 Imines: CH3NH, CH3CHNH, HNCHCN – Nearly all molecular lines are in absorption via transitions between low energy states (<30 K).

Above: Continuum image of Sgr B2(N) at 41 GHz, overlaid with integrated emission line contours of the

2-1 transition of CH2CN and the 404 - 303 and 505 - 404 transitions of E-HNCHCN. Dashed line contours are in absorption. All data is taken with the ATCA.

Left: Continuum image of Sgr B2(N) at 18 GHz, overlaid with integrated emission line contours of 18 –

20GHz transitions of HC3N, CH3CN, CH2CHCN,

CH3CH2CN, and CH2CN. Dashed line contours are in absorption. Data is from the Karl G. Jansky VLA. References 1. Law et al. (2003), AJ, 126, 1871. 2. Gaume et al. (1995), ApJ, 449, 663. 3. Mehringer & Menten (1997), ApJ, 474, 346. 4. Snyder, Kuan & Miao (1994), LNP, 439, 187.