The Latest in Radio Astronomy Surveys of Star Formation Towards the Center of our Galaxy Matthew Rickert

Transcription

1 F. Yusef-Zadeh (Northwestern University) J. Ott (National Radio Astronomy Observatory) Search for Water and Ammonia towards the Galactic Center (SWAG) The Latest in Radio Astronomy Surveys of Star Formation Towards the Center of our Galaxy Matthew Rickert (Northwestern University)

2 The Galactic Center: Central Molecular Zone (CMZ) CMZ Longmore et al MNRAS 429

3 The Galactic Center: Central Molecular Zone (CMZ) Inner ~400 pc Molecular Gas 5 % (~ 5 x 10 7 M Θ ) Dense (~10 4 cm -3 )

4 The Galactic Center: Star Formation in the CMZ CMZ Longmore et al MNRAS 429

5 Star Formation in the CMZ Longmore et al MNRAS 429

6 Question 1: Is the CMZ inefficient at forming stars? Possible Solution: Conduct a sensitive untargeted survey that can detect more star formation

7 Distribution of Star Formation Yusef-Zadeh et al ApJL 764

8 Distribution of Star Formation Yusef-Zadeh et al ApJL 764

9 Yusef-Zadeh et al ApJL 764 Distribution of Star Formation 2/3 of the molecular gas

10 Distribution of Star Formation

11 Distribution of Star Formation

12 Distribution of Star Formation

13 Distribution of Star Formation

14 Distribution of Star Formation 2/3 of the molecular gas

15 Question 2: Is the distribution of star formation asymmetric? Possible Solution: Use an untargeted survey that isn t susceptible to absorption

16 Water (22 GHz) Maser Collisionaly Pumped Bright Don t suffer from absorption Not Unique to Star Formation Not many (37) McCaughrean,

17 Methanol Masers (6.7 GHz) Radiatively Pumped Biased towards high mass ( 8 M ʘ ) Don t suffer from absorption Bright (100s Jy) Not many (23)

18 Chambers et al A&A 563 Previous Works: Water masers Methanol masers Sgr B2 Sgr B2

19 Solution: Conduct high resolution high sensitivity survey of water and methanol masers

20 My Work: VLA Finley, D., NRAO and Associated Universities, Inc.

21 High resolution=more detections Detection Limit Source * = Telescope Response (Beam) Observation Detection Limit

22 T [K] My Work: VLA vs Mopra resolution Mopra 4km/s S [Jy] VLA km/s Flux Density (Jy/Beam) V LSR (km/s) <2 Chambers et al A&A 563 Finley, D., NRAO and Associated Universities, Inc.

23 astronomy.swin.edu.au Finley, D., NRAO and Associated Universities, Inc. My Surveys ATCA water (SWAG) VLA methanol OTF VLA water (imaging) LARGE data size >70 TB

24 Calibrated and imaged by Nico Krieger (Max Planck Institut für Astronomie) astronomy.swin.edu.au My Work: ATCA Water Survey ~250 maser locations factor of 6 improvement

25 My Work: ATCA Water Survey

26 Water vs IR Distributions Water 2/3 of the molecular gas IR 2/3 of the molecular gas

27 My Work: VLA Methanol Survey ~50 maser locations Factor of 2 improvement

28 My Work: VLA Methanol Survey ~50 maser locations Factor of 2 improvement 2/3 of the molecular gas

29 Methanol vs IR Methanol 2/3 of the molecular gas Distributions IR 2/3 of the molecular gas

30 Methanol vs IR Methanol 2/3 of the molecular gas Distributions IR 2/3 of the molecular gas

31 Methanol vs IR Methanol 2/3 of the molecular gas Distributions IR 2/3 of the molecular gas

32 Summary Low number of young stellar objects per mass of gas in CMZ Conducted 1 st high resolution surveys of water and methanol masers in CMZ, got many new detections Water masers are uniformly distributed along Galactic longitude, methanol masers are not

33 Star Formation across Galaxies Yusef-Zadeh et al ApJ 702 Kennicutt et al ARAA 50

34 Current Work: Characterize Spectra Example: ID outflows 0.04 pc

35 Water Masers: Contaminated by Evolved Stars?

36 Previous Work: Mopra + Water masers (22 GHz) ο Methanol masers (6.7 GHz) Star formation occurs on different timescale in the CMZ? Breen et al. 2010MNRAS Chambers et al A&A 563

37 The Galactic Center: Star Formation Hansen, et al. Stellar Interiors 2004

38 Current Work: ID YSOs Ramirez et al ApJS 175

39 Finley, D., NRAO and Associated Universities, Inc. Current Work: VLA: Upgrades Replaced ALL electronics Receivers Wave guides Cables Correlator Improved: Sensitivity Frequency range Frequency resolution