1. The Arecibo Legacy Fast ALFA Extragalactic HI Survey: (The Search for Low-Mass, Gas-Rich Halos) Martha Haynes (Cornell University) for the ALFALFA team ALFALFA:

2. ALFA is not a car… Arecibo L-band Feed Array It is a radio “camera”

3. ..on Arecibo 305m telescope

4. An extragalactic spectral line survey Covers 7000 sq deg of high galactic latitude sky 1345-1435 MHz (-2000 to +17500 km/s for HI line) 5 km/s resolution 2-pass, drift mode (total int. time per beam ~ 40 sec) 1.5-2 mJy rms 4000 hrs of telescope time, 6-7 years started Feb 2005; as of end of 2006, 1/3 complete One of several major surveys currently ongoing at Arecibo, exploiting its new multibeam capability http://egg.astro.cornell.edu/alfalfa ALFALFA as a Legacy Survey

5. Peebles (2000) Halo mass function in voids : Gottlöber et al (2003) Cosmic voids are filled with low mass dark matter haloes ~1000 haloes with M < 10 9 M  and v rot < 20 km/s in a 20 h -1 Mpc void are predicted v rot >55km/s The Void Phenomenon

6. Void galaxies in the SDSS : Hoyle et al (2005) Void LF has a faint M* but a similar faint-end slope, compared to the overall LF Void galaxies are blue, disk-like and have high H  equivalent width Luminosity function of void galaxies

7. The “Missing Satellite Problem” Models/simulations predict large numbers of satellites Kauffmann et al. (1993) Klypin et al. (1999) The current census does not count them. Faint end slope of the optical LF Faint end slope of the HIMF Willman et al. (2005) suggest that more than half of the MW satellites have not been identified because of extinction, surface brightness limits Nothing to detect? Baryon loss during reionization ( e.g., Efstathiou 1992; Barkana & Loeb 1999; Shaviv & Dekel 2003) Can they (ever) form stars? (Verde et al. 2002)

8. Dwarf galaxies dE, dSph, dIrr Low mass: detected only nearby Dark matter dominated Low abundances Stellar mass: 10 6 -10 8 M  Blue Luminosity: 10 6 -10 8 L  (M B > -15) Dynamical mass: 10 7 -10 9 M  Where they are gas-rich : HI mass: 10 6 -10 8 M  Sometimes, extensive HI Evidence for dark matter “Dwarf galaxies of the Local Group” Mateo 1998 ARAA Leo A Sagittarius LGS3 Carina IZw18 SBS0335-052

9. Substructure in the Local Group Diagram from Grebel 1999 Giant spirals dSph (+dEll) dIrr dIrr/dSph Galaxies mainly clustered around the two principal galaxies MW & M31 Morphological segregation evident dE/dSph near large galaxies dI at larger distances

10. The Search for Low Mass Halos Do large numbers of low mass “halos” exist? If so, do they contain baryons? If so, could they be “starless” but gas-rich? => Extragalactic HI survey If so, could they be found preferentially in some environments but not in others? => “Fair sample” ALFALFA is designed to detect low mass gas-rich halos

11. Parkes HIPASS survey: Zwaan et al. 2003 ? The HI Mass Function Previous surveys have included few (if any) objects with HI masses less than 10 8 M . At lowest masses, differ by 10X: Rosenberg & Schneider (2000) versus Zwaan et al. (1997)

12. Environment & the HIMF Previous studies based only on Virgo have suggested that the HIMF in Virgo is shallower than in the field Only a single cluster Very small number statistics Is this just HI deficiency? Watch out for morphological biases Springob, Haynes & Giovanelli (2005) Much larger sample, but optically targeted Used PSCz density field out to 6000 km/s Low mass end of HIMF in high density regions flatter and M* lower Cannot be explained simply by morphology or HI deficiency. Zwaan et al. (2005): HIPASS seems inconsistent ALFALFA will provide needed statistics and be HI blind.

13. Previous surveys for HI in voids for example: Weinberg et al 1991 (PPS & foreground void) Szoromu et al 1994 Szomoru et al 1993 (HI in Bootes void galaxy) Szomoru et al 1996a (Bootes void) Szomoru et al 1996b Pustilnik et al 2002 (Blue compact galaxies)

14. HI in “famous” voids VLA surveys: Szomoru et al (1996): Bootes void

15. HI in “famous” voids VLA surveys: Szomoru et al (1996): Bootes void

16. HI in “famous” voids VLA surveys: Szomoru et al (1994): PPS & foreground void VoidPPS # fields3012 Int. time/field40 min210 min rms/beam1 mJy0.4 mJy # detections017 Serious limitations: Relatively small volume sampled Bandwidth only 6.25 MHz (1200 km/s) Velocity resolution ~42 km/s (too wide)

17. ALFALFA Survey Commensal with TOGS HI Does not compete with galactic plane surveys High galactic latitude sky visible from AO Supergalactic plane VirgoLeo

18. 1.Determination of the faint end of the HI Mass Function and the abundance of low mass gas rich halos 2.Environmental variation in the HI Mass Function 3.Blind survey for HI tidal remnants 4.Determination of the HI Diameter Function 5.The low HI column density environment of galaxies 6.The nature of HVC’s around the MW (and beyond?) 7.HI absorbers and the link to Ly  absorbers 8.OH Megamasers at intermediate redshift 0.16 < z < 0.25 ALFALFA Science Goals

19. ALFALFA as a Blind HI Survey HI mass and distribution (for extended objects) Normal, star-forming disks Potential for future star formation (HI content) HI deficiency in clusters History of tidal events Low mass, LSB dwarfs HI absorption: optical depth Link to Ly-α absorbers Redshifts Rotational velocities Dark matter Distances via Tully-Fisher relation HI in M31 Credit: R. Braun ∫ SdV HI mass V Distance ∆V Mass

20. ALFALFA as a Blind HI Survey HI mass and distribution (for extended objects) Normal, star-forming disks Potential for future star formation (HI content) HI deficiency in clusters History of tidal events Low mass, LSB dwarfs HI absorption: optical depth Link to Ly-α absorbers Redshifts Rotational velocities Dark matter Distances via Tully-Fisher relation Credit: A. Chung

21. ALFALFA as a Blind HI Survey HI mass and distribution (large objects) Normal, star-forming disks Potential for future star formation (HI content) HI deficiency in clusters History of tidal events Low mass, LSB dwarfs HI absorption: optical depth Link to Ly-α absorbers Redshifts Rotational velocities Dark matter Distances via Tully-Fisher relation Durrell & DeCesar; +Yun 1994

22. ALFALFA as a Blind HI Survey HI mass and distribution (large objects) Normal, star-forming disks Potential for future star formation (HI content) HI deficiency in clusters History of tidal events Low mass, LSB dwarfs HI absorption: optical depth Link to Ly-α absorbers Redshifts Rotational velocities Dark matter Distances via Tully-Fisher relation I Zw 18 van Zee et al. 1998

23. Carignan & Beaulieu 1989 VLA D HI Arecibo map outer extent [Hoffman et al. 1993] Extent of Optical image M H = 2.5 x 10 8 M  M stars = 5.0 x 10 7 M  M Dyn = 3.0 x 10 9 M  DDO154 Are there totally “dark” galaxies?

24. Optical galaxy Giovanelli, Williams & Haynes 1989 HI 1225+01 MLML > 200

25. ALFALFA is a collaboration of >50 people, from 34 institutions in 13 countries. ALFALFA is an open collaboration: anybody with a valid scientific interest and a hardworking disposition can join. The ALFALFA Team Legacy survey on a national telescope used not only for radio astronomy but also radar studies of Solar System objects and the Earth’s upper atmosphere Heavy student involvement Broad institutional representation

26. Cornell University NAIC NRAO Lafayette College Union College Wesleyan University Harvard/Smithsonian CfA U. of Michigan Indiana U. Rutgers U. U. of Minnesota U. of Wisconsin St. Lawrence U. Humboldt St. U. Colgate U. Georgia Southern U. NRL NASA/GSFC U. of Crete U. of Tel-Aviv U. of Rome U. of Milan II Obs. Of Brera U. of Provence Arcetri Astrophys. Obs. Lab. D’Astrophysique/Marseille Cardiff U. U. de Barcelona U. de Cordoba (Argentina) NCRA/GMRT (India) P. U. Cat. de Chile Special Astrophys. Obs. (Russia) U. of Kiev Participating Institutions

27. Beam dilution To sample more deeply, you have to integrate A LOT longer! ALFALFA: a wide area survey For low masses: larger solid angle Giovanelli et al. 2005, AJ130, 2598 …

28. ALFA beams are 3.3’x3.8’ “Almost” fixed azimuth drift mode 2 nd pass offset from the first to give 1.05’ sampling ALFALFA strategy: Keep it simple!

29. ● Signal extraction in the Fourier domain by Amélie Saintonge – Match filter over a range of widths of the template ● e.g. 10 km/s – 600km/s – Choose the width for which the convolution is maximized - -> position of the signal – Calculate the amplitude of the signal from the width Slide: Amelie Saintonge Run on 3-D datacubes after completion of “tile” Once signals identified, further interactive analysis Automated signal detection

30. Exploit VO tools during data processing Data processing tools developed here at CU are now running at 11 other institutions VO tools incorporated to allow access to external datasets during data processing DSS, DSS2, Sloan, 2MASS, NVSS images can be fetched NED and other on-line catalogs, including our own, can be accessed and overplotted.

31. VO portal http://arecibo.tc.cornell.edu/hiarchive ALFALFA data & products will be made public as soon as possible. Targeted HI survey and precursor data already available Remember: we need a complete dataset – both passes – to make a grid. Issue is serving data volume/local cpu: “google ALFALFA”

32. Current Status (by 15 Dec 2006) Total # blocks177145 Total hours1070690 In map region1010625 07h30 – 16h30 +04 to +16 deg 22h00 – 03h00 +12 to +16 deg +24 to +32 deg 1/3 of survey covered with 2 passes (by 15Jan07) Processing requires complete sky coverage Riccardo will present only 4% of final survey…

33. Survey Beam Area rms min M HI N det t s N los arcmin sq. deg. (mJy @ 18 km/s) @ 10 Mpc sec AHISS 3.3 13 0.7 2.0x10 6 65 var 17,000 ADBS 3.3 430 3.3 9.6x10 6 265 12 500,000 HIPASS 15. 30,000 13 3.6x10 7 4315 460 1.9x10 6 HIJASS 12. (TBD) 13 3.6x10 7 (?) 3500 (TBD) J-Virgo 12 32 4 1.1x10 7 31 3500 3200 HIDEEP 15 32 3.2 8.8x10 6 129 9000 2000 ALFALFA 3.5 7,000 1.7 4.4x10 6 20,000+ 30 7x10 6 ALFALFA will be ~ 1 order of magnitude more sensitive than HIPASS with 4X better angular resolution, 3X better spectral resolution, and 1.6X total spectral bandwidth Comparison of blind HI surveys

34. Giovanelli et al 2005 AstronJ 130, 2598 & 2613 * Aug-Sep 2004 * Candidate Detections Confirmation Run Jan-Feb 2005 * 36 hours of ALFA data 166 confirmed HI sources : - 25 with HI mass > 10 10 M  - 4 with HI mass < 10 7 M  (twice as many as all of HIPASS) - high positional accuracy => optical counterparts ID’d - slightly better detection rate than expected (high side), i.e. our ability to reliably dig in low S/N territory is high - system hardware performance, “hands-off” bandpass calibration and baselining (IDL processing pipeline) yield EXCELLENT data quality ALFALFA Precursor

35. F Integrated Flux of 1 Jy km/s HIPASS Completeness Limit HIPASS Detection Limit HIPASS would have detected only a handful; and none of the low mass ones. Precursor (ALFA commissioning phase) results In 36 hours, we detected 4X more lowest mass objects than all of HIPASS

36. First ALFALFA catalog Giovanelli et al (2006, Astron. J. submitted) Northern Virgo cluster region 11 h 44 m < R.A. < 14 h 00 m +12º < DecJ < +16º 716 detections of good/excellent quality Median redshift 7000 km/s In the same sky region, HIPASS detected only 40 objects. HIJASS Virgo survey: region of maximum sensitivity: ALFALFA: 193 detections HIJASS: 13

37. ALFALFA: Hunting in/around voids HI mass function to low masses, and its environmental dependence HI detections + HST distances => shapes and kinematics of voids Tikhonov & Karachentsev 2006 astro-ph/0609109 Evolutionary history of isolated (never interacting!) galaxies ALFALFA is designed to hunt for low mass systems efficiently High sensitivity (Arecibo = 1/10 th SKA!) Efficient: 97% “open shutter” time Large solid angle (7000 sq deg) Moderate angular resolution (~3.5’) => optical i.d. - or none! High spectral resolution (5 km/s) “Minimum intrusion” => high data quality Dual pol/2 pass coverage (confirmation) Automated signal detection

38. Riccardo will talk next, after tea