ALFALFA The Arecibo Legacy Fast ALFA Extragalactic HI

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

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

. . on Arecibo 305 m telescope

ALFALFA as a Legacy Survey • One of several major surveys currently ongoing at Arecibo, exploiting its new multibeam capability • • 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 m. Jy rms 4000 hrs of telescope time, 6 -7 years started Feb 2005; as of end of 2006, 1/3 complete http: //egg. astro. cornell. edu/alfalfa

The Void Phenomenon Peebles (2000) • Cosmic voids are filled with low mass dark matter haloes vrot>55 km/s • ~1000 haloes with M < 109 M and vrot< 20 km/s in a 20 h-1 Mpc void are predicted Halo mass function in voids : Gottlöber et al (2003)

Luminosity function of void galaxies • 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 Void galaxies in the SDSS : Hoyle et al (2005)

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)

Dwarf galaxies Leo A Sagittarius LGS 3 • • d. E, d. Sph, d. Irr Low mass: detected only nearby Dark matter dominated Low abundances Stellar mass: 106 -108 M Blue Luminosity: 106 -108 L (MB> -15) Dynamical mass: 107 -109 M Where they are gas-rich: • HI mass: 106 -108 M • Sometimes, extensive HI • Evidence for dark matter “Dwarf galaxies of the Local Group” Mateo 1998 ARAA Carina IZw 18 SBS 0335 -052

Substructure in the Local Group • Galaxies mainly clustered around the two principal galaxies MW & M 31 • Morphological segregation evident • d. E/d. Sph near large galaxies • d. I at larger distances Diagram from Grebel 1999 Giant spirals d. Sph (+d. Ell) d. Irr/d. Sph

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

The HI Mass Function • Previous surveys have included few (if any) objects with HI masses less than 108 M. ? • At lowest masses, differ by 10 X: Rosenberg & Schneider (2000) versus Zwaan et al. (1997) Parkes HIPASS survey: Zwaan et al. 2003

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.

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 1996 a (Bootes void) • Szomoru et al 1996 b • Pustilnik et al 2002 (Blue compact galaxies)

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

HI in “famous” voids VLA surveys: • Szomoru et al (1994): PPS & foreground void Void PPS # fields 30 12 Int. time/field 40 min 210 min rms/beam 1 m. Jy 0. 4 m. Jy # detections 0 17 Serious limitations: • Relatively small volume sampled • Bandwidth only 6. 25 MHz (1200 km/s) • Velocity resolution ~42 km/s (too wide)

ALFALFA Survey • Commensal with TOGS HI High galactic latitude sky visible from AO • Does not compete with galactic plane surveys Supergalactic plane Virgo Leo

ALFALFA Science Goals 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 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 M 31 Credit: R. Braun ∫ Sd. V V ∆V HI mass Distance Mass

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

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 & De. Cesar; +Yun 1994

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

Are there totally “dark” galaxies? Arecibo map outer extent [Hoffman et al. 1993] DDO 154 MH = 2. 5 x 108 M Mstars = 5. 0 x 107 M MDyn = 3. 0 x 109 M Extent of Optical image Carignan & Beaulieu 1989 VLA D HI

HI 1225+01 Optical galaxy M > 200 L Giovanelli, Williams & Haynes 1989

The ALFALFA Team • 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. • 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

Participating Institutions • Cornell University • NAIC • NRAO • Lafayette College • Union College • Wesleyan University • Harvard/Smithsonian Cf. A • 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

ALFALFA: a wide area survey Beam dilution Giovanelli et al. 2005, AJ 130, 2598 To sample more deeply, you have to integrate A LOT longer! … For low masses: larger solid angle

ALFALFA strategy: Keep it simple! ALFA beams are 3. 3’x 3. 8’ “Almost” fixed azimuth drift mode 2 nd pass offset from the first to give 1. 05’ sampling

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

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, DSS 2, Sloan, 2 MASS, NVSS images can be fetched • NED and other on-line catalogs, including our own, can be accessed and overplotted.

VO portal • 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” http: //arecibo. tc. cornell. edu/hiarchive

Current Status (by 15 Dec 2006) Total # blocks 177 145 Total hours 1070 690 In map region 1010 625 07 h 30 – 16 h 30 22 h 00 – 03 h 00 +04 to +16 deg +12 to +16 deg +24 to +32 deg • 1/3 of survey covered with 2 passes (by 15 Jan 07) • Processing requires complete sky coverage • Riccardo will present only 4% of final survey…

Comparison of blind HI surveys Survey Beam arcmin Area rms min MHI Ndet 65 265 4315 (? ) 31 129 sq. deg. (m. Jy @ 18 km/s) @ 10 Mpc AHISS ADBS HIPASS HIJASS J-Virgo HIDEEP 3. 3 15. 12 15 13 430 30, 000 (TBD) 32 32 0. 7 3. 3 13 13 4 3. 2 2. 0 x 10 6 9. 6 x 10 6 3. 6 x 10 7 1. 1 x 10 7 8. 8 x 10 6 ALFALFA 3. 5 7, 000 1. 7 4. 4 x 106 20, 000+ ts sec Nlos var 17, 000 12 500, 000 460 1. 9 x 106 3500 (TBD) 3500 3200 9000 2000 30 7 x 106 ALFALFA will be ~ 1 order of magnitude more sensitive than HIPASS with 4 X better angular resolution, 3 X better spectral resolution, and 1. 6 X total spectral bandwidth

ALFALFA Precursor Giovanelli et al 2005 Astron. J 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 > 1010 M - 4 with HI mass < 107 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

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

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 < Dec. J < +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

ALFALFA: Hunting in/around voids 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 • 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

Riccardo will talk next, after tea