An NH 3 Survey Program with the Radio Telescope of Hokkaido University

1. 4th International Symposium on New Trends of Physics Recent Advances in Astrophysics and Planetary Science – from the early universe to the Solar system – An NH3 Survey Program with the Radio Telescope of Hokkaido University Division of Physics, Graduate School of Science, Hokkaido University Kazuo Sorai, Asao Habe, Johta Awano, Sakurako Sumida, Yoshiaki Fukuya, Ryosuke Uchida, Hiroyuki Nishitani, Keita Hosaka, Yoshimasa Watanabe, Noboru Kaneko, Masayuki Fujimoto, and Tomakomai 11-m Telescope Team

2. I. INTRODUCTION Where are stars formed? ・ molecular clouds > dense cores What conditions are needed for star formation? ・ density, temperature, … ・ massive stars, low mass stars ・ clusters, isolated stars density fluctuation formation of molecular cores formation of protostars formation of star or star clusters

3. I. INTRODUCTION What is a good tracer of molecular cores? Object Class ncrit [cm-3] Tracer cloud complex ~ 10212CO cloud ~ 10313CO core ~ 103 – 4 C18O dense core 103 – 4 NH3 104 CS 104 – 5 H13CO+ 13CO Ha, radio recombination lines (RRLs) 12CO C18O NH3 IR

4. I. INTRODUCTION Previous observations on molecular gas ・ lower density gas large surveys 12CO J=1–0 : CfA, FCRAO J=2–1 : Univ. of Tokyo 12CO, 13CO, C18O J=1–0 : NANTEN ・ dense cores small area / single positions NH3 : Benson & Myers (1989) 149 dark clouds (J, K) = (1, 1), (2, 2) Haystack 37m & NRAO 43m telescopes optical band 12CO J=1–0 NASA

5. I. INTRODUCTION nitrogen hydrogen NH3 molecule ・ symmetric top molecule ・ energy level rotational quantum number: J projection of J on the molecular axis: K Inversion transitions of NH3 ・ J = K≠ 0  2 levels ・ many transitions in a narrow band (J, K) = (1, 1): 23.694 GHz (2, 2): 23.723 GHz (3, 3): 23.870 GHz (4, 4): 24.139 GHz  Simultaneous observations are possible with a same telescope.

6. I. INTRODUCTION Tracer of dense molecular gas ・ higher critical density: ncrit ~ 104 cm-3 Tracing molecular gas temperature ・ rotation temperature: Trot energy of upper state integrated intensity ・ accurate estimation of Trot several lines in a narrow band ・ not so different from kinetic temperature Trot≲Tkin Ho & Townes (1983)

7. II. OUR RADIO TELESCOPE Tomakomai 11m Radio Telescope ・ Moved from Miura (near Yokohama) ・ S/X-band VLBI system  K-band single-dish/VLBI system || || 2/8 GHz band ~ 22 GHz band Asahikawa Sapporo ~ 70 km Tomakomai Hakodate

8. II. OUR RADIO TELESCOPE Receiver 1st IF Converter E/O O/E 1st IF Distributor IF Signal Selector 2nd IF Converter Spectrometer VLBI Video Converter Auto Level Controller Spectrometer Spectrometer IP-VLBI Data Sampler IF Control PC K4 Recorder Antenna Control Unit Observation Control PC Remote Control PC (Sapporo) K-band Receiving System

9. II. OUR RADIO TELESCOPE Specification of the Telescope ・ Telescope Diameter 11 m Angular Accuracy 18 arcsec Angular Resolution 5 arcmin ・ Receiver Observed Band 21.3 – 24.3 GHz Polarization LHCP Noise Temperature 46 K ・ IF 1st IF Band 4 – 7 GHz 2nd IF Band 0.5 – 1.0 GHz Video Band DC – 32 MHz 3rd IF Band 16 – 32 MHz ・ Backend Spectrometer Type Digital FX (single dish) Bandwidth 16 MHz Channels 2048 (VLBI) Recorder Type K4 / IP-VLBI

10. III. OUR OBSERVATION PROGRAM Previous observations of NH3 lines ・ observations toward a single position dark clouds : Myers & Benson (1983), Benson & Myers (1989) ultracompact HII regions: Churchwell et al. (1990) ・ mapping or interferometer observations Orion : Ho et al. (1979), Cesaroni & Wilson (1984) the Galactic center : Coil & Ho (2000), McGary, Coil, & Ho (2001) Ho et al. (1979) Cesaroni & Wilson (1984) McGary, Coil, & Ho (2001) Nagahama et al. (1998)

11. III. OUR OBSERVATION PROGRAM The goal of our observational studies ・ How are dense molecular cores distributed over wider area? e.g., entire clouds, cloud complexes, the Galaxy ・ What are physical conditions of dense gas like? temperature, density ・ Are there any differences of the conditions from one position to another? e.g., ridge and edge of a cloud, arm and interarm, innter and outer Galaxy  star formation scenario in the Galaxy NASA

12. III. OUR OBSERVATION PROGRAM NH3 Survey toward the Galactic Star Forming Regions ・ Orion: bright, massive star forming region ・ Taurus: low mass star formation ・ Cygnus: the local arm ・ W3: star formation in the outer Galaxy ・ M17: test observation ・ the Galactic center: star formation in the nuclear region (Dame, Hartmann, & Thaddeus 2001)

13. III. OUR OBSERVATION PROGRAM An example – M17 ・ grid spacing: 2.5 arcmin ・ frequency resolution: 31.25 kHz ~ 0.4 km s-1 ・ integration: 1 hour ・ rms noise: 13 mK ・ total positions: 54  entire molecular cloud 2 months C18O J=2–1 Güsten & Fiebig (1988) (Wilson, Hanson, & Muders 2003)

14. IV. TEST OBSERVATIONS (J, K) = (1, 1) 0.2 TA* [K] 0.1 0.0 (J, K) = (2, 2) 0.2 TA* [K] 0.1 0.0 100 -100 -50 0 50 VLSR [km s-1] Observation and Results – DR21 ・ Integration: 20 min. ・ Freq. Resolution (8ch bound): 62. 5 kHz ~ 0.8 km s-1@ 23GHz ・ rms noise: ~ 16 mK ・ Tsys: ~ 100 K TA* (1, 1) = 0.22 K TA* (2, 2) = 0.11 K with satellite components TA* (3, 3) = 0.07 K (~2.5s) t = 0.77, Trot = 20 ± 4 K (Sumida 2005)

15. IV. TEST OBSERVATIONS 0.1 (J, K) = (1, 1) TA* [K] 0.0 (J, K) = (2, 2) -0.1 (J, K) = (3, 3) 40 -40 -20 0 20 VLSR [km s-1] Observation and Results – S140/L1204 ・ Integration: 23 min. ・ Freq. Resolution (4ch bound): 31.25 kHz ~ 0.4 km s-1@ 23GHz ・ rms noise: ~ 35 mK ・ Tsys: ~ 150 K TA* (1, 1) = 92 mK with satellite components ? no detection of (2, 2), (3, 3)

16. V. SUMMARY ・ We will just start observation with the radio telescope of Hokkaido University. ・ Our main program is NH3 survey toward the Galactic star forming regions. ・ The goal of the program is to reveal physical conditions of star formation in a scale from a molecular cloud to the Galaxy.