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I-GALFA: Mapping the Inner Galactic Disk using H.I. Spectroscopy

I-GALFA is a 2-year survey that maps the inner Galactic disk using H.I. spectroscopy. It explores molecular cloud formation, massive star energetics, and the detailed structure of the Galaxy. Commensal partners include ZOA and GALFACTS.

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I-GALFA: Mapping the Inner Galactic Disk using H.I. Spectroscopy

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  1. Bon-Chul Koo, Geumsook Park Ji-hyun Kang Kevin Douglas Josh Peek Eric Korpela, Carl Heiles Tom Bania Seoul National U. NAIC Exeter U. Columbia U. U. Cal-Berkeley Boston U. I-GALFA: The Inner-Galaxy ALFA H I Survey Steven Gibson W. Kentucky U. Arecibo Surveys Workshop, NAIC, December 10, 2009

  2. I-GALFA Overview • Quick (2-year) lean (8-member) survey • Map inner Galactic disk H I (330 hrs, 1100 deg2) • GALFA H I spectrometer, methods, pipeline • Base Trms ~ 0.25 K for 3.35’ beam, 0.184 km/s chan. • Science • Molecular cloud formation • Shells + chimneys related to massive star energetics • Detailed structure of Galaxy, on and off plane • Commensal partners: ZOA + GALFACTS • Thanks to NAIC for scheduling!

  3. I-GALFA Sky Coverage • Completed in 2009 September! • Will merge with other GALFA - H I surveys • RA+DEC fields covering |GLAT| < 10 degrees over full AO DEC range • 4 major fields (ZA nod on meridian, 0.84’/s) • 1 ``zenith’’ field (AZ wag 51m W of zenith, 0.59’/s) • Some latitude extensions due to CIMA quirks and schedule resolution – all useful!

  4. I-GALFA Commensality • First doubly-commensal ALFA survey project • I-GALFA (a2186) was primary (GALSPECT) • ZOA (a2144) + GALFACTS (a2390) commensal • shared WAPPs in 2008, Mocks in 2009 • GALFACTS pipeline bins time samples for ZOA data • Commensal needs + challenges • GALFACTS: rapid sampling, radar RFI filter, winking cal • ZOA: fine spectral resolution, good redshift coverage • Commensal benefits • Time efficiency • CIMA development (fastbasket 2006-2008, smartbasket 2009) • Same methods now used for GALFACTS (a2130) + TOGS2

  5. I-GALFA Observing • Procedures adapted from Perseus (a2174) and other GALFA - H I projects • Testing / hairy observations handled by obs. team • Routine observations by telescope operators • Each session assigned an obs. team member: • Prepare observing scripts for operator to run • On call during run in case of problems • Run daily bookkeeping scripts, update logs, etc. • All sessions logged on I-GALFA website

  6. I-GALFA Data • Processing team (Douglas, Kang, Peek) ran GSR pipeline on all GALSECT data • Challenges near plane spur pipeline development (broader lines, brighter emission) • Data still being improved in next few months • Processed data assembled in cubes (Gibson) • Currently proprietary to science team • Initial public release in 2010; full release in 2011 • I2 ‘narrow’ and ‘wide’ copies of each cube (1 GB) • R4 full-spectrum cubes eventually (8 GB) • Both RA+DEC and GLON+GLAT coordinates

  7. I-GALFA and the NVO • Public release data to be on GALFA - H I website • Cornell + other sites (?) -- redundancy is good! • Useful NVO interface features • Level 1: pre-generated atlas tile cubes (list or map) • Level 2: cutout image cubes on same atlas pixel grid • Level 3: arbitrary mosaic cubes regridded from atlas • Ancillary Data: • 2-D cube projections [(l,b), (l,v), etc.] of I-GALFA H I • NVO hooks to other ALFA data (e.g. GALFACTS, RRL) • NVO hooks to multi-l data (e.g., SkyView)

  8. First I-GALFA Science: Gas Structures

  9. First I-GALFA Science: Gas Structures

  10. First I-GALFA Science: Gas Structures 500 pc Distance ~ 3 kpc => 3.4’ ~ 3 pc

  11. NGC 891 Optical Dust Worms (WIYN 3.5m; Howk & Savage 1997) Distance ~ 9.5 Mpc Ground 1” ~ 48 pc HST 0.05” ~ 2.4 pc (H I has velocity!)

  12. First I-GALFA Science: Cold H I Emission Newly forming disk-halo molecular clouds?

  13. First I-GALFA Science: H I Self-Absorption Riegel-Crutcher Cold Cloud fragments?

  14. Supershell GSH 041+01+27 Multiple SNe or HVC Colliding with Disk Downes et al (1981) polarized continuum GALFACTS polarimetry pending

  15. H I Structure: Inner vs. Outer Galaxy In the inner Galaxy, small filamentary structures perpendicular to the plane dominate. In the outer Galaxy, long filaments parallel to the plane dominate. Massive stars, turbulence? Power spectrum? Inner galaxy at +80 km/s Outer galaxy at -80 km/s

  16. I-GALFA Publications, etc. • Koo et al., 2009, IAU Special Session 8 on Galactic plane, Highlights of Astronomy, in press (survey overview talk) • Gibson et al., in preparation for AJ (survey technical paper) • Forthcoming science papers (2010) • Gibson et al., in prep for ApJ (cold H I and H2 in extraplanar clouds) • Koo et al., in prep for ApJ (disk-halo H I whiskers + filaments) • Kang et al., in prep for ApJ (forbidden velocity wing H I shells) • Sidorin et al., in prep for A&A (H I analogs of GLIMPSE IR shells) • Douglas et al., in prep for ApJ (gas-dust relations in extraplanar clouds) • Ph.D. theses in progress: Geumsook Park, Vojtech Sidorin • Undergrad research: Sean Stopher, Aaron Bell • Outreach: public talks on Arecibo using GALFA images – WKU student clubs, gifted Kentucky high school students, etc.

  17. Acknowledgements • Telescope operators: Israel Cabrera, Edgardo Cruz, Norberto Despiau, Elliot Gonzalez, Juan Marrero, Wilfredo Portalatin • Other NAIC staff: Mikael Lerner, Phil Perillat, Arun Venkataraman, Ganesan Rajagopalan, Hector Hernandez, and many others • ZOA + GALFACTS commensal partners: Trish Henning, Robert Minchin, Russ Taylor, Chris Salter, Tapasi Ghosh, Jeff Dever, Jeroen Stil, and many others • GALFA - H I scripts, pipeline: Peek, Heiles, Stanimirovic, Krco • I-GALFA observing team: Koo, Kang, Park, Korpela, Gibson • I-GALFA data team: Douglas, Kang, Peek, Gibson • Grants from NSF, Korean Research Foundation, Marie Curie fellowship

  18. End

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