Presentation on theme: "Deep Neutral Hydrogen Surveys with the Arecibo 305-m Telescope – the Arecibo Galaxy Environment Survey Robert Minchin NAIC Arecibo Observatory."— Presentation transcript:
Deep Neutral Hydrogen Surveys with the Arecibo 305-m Telescope – the Arecibo Galaxy Environment Survey Robert Minchin NAIC Arecibo Observatory. The HIMF from the first 45 sq. deg. of AGES (Davies et al. 2011) is shown below, with the ALFALFA (Martin et al. 2010) and HIPASS (Zwaan et al. 2005) HIMFs overlaid. We also show the AGES HIIMFs from the Virgo (Taylor 2010) and Abell 1367 (Cortese et al. 2008) clusters (normalized to their peaks). It can be seen that the overall AGES HIMF is steeper (by about 2σ) at the faint end than those derived from the shallower surveys. If this difference is real, the most likely explanation is large scale structure – either a local underdensity is giving too low a number of small galaxies in the shallower surveys, or the various targeted structures are giving an overdensity of small galaxies in AGES. To check for the latter, the AGES HIMF was re-calculated excluding groups and clusters and excluding the super-galactic plane, with the result that the steep slope remains present. Combining the AGES data with data from the (similar depth) ALFA Zone of Avoidance survey will give much better statistics and enable us to see if there really is a difference between the deep ALFA surveys and ALFALFA. Neutral hydrogen surveys have the potential to investigate how cosmic structures form and evolve and how baryons cycle in and out of galaxies. AGES is the deepest wide-area neutral hydrogen survey to date, reaching noise levels of 0.7 mJy/beam at a velocity resolution of 10 km s -1. The survey is designed to sample the full gamut of galaxy environments, from the underdensity of the Local Void through to the Virgo Cluster. The full survey will cover 200 sq. deg. when complete, so far 65 sq. deg. have been observed to full depth. The full-depth fields include isolated galaxies (UGC 2082, NGC 1156), galaxy pairs (NGC 7332), galaxy groups (NGC 7448), and galaxy clusters (Virgo, Abell 1367). As well as the targeted environments, each cube also includes a ‘blind’ volume out to z~0.06 – expanding to z~0.15 for the second half of the survey. Renzogram showing HI being stripped from NGC 7339 by NGC 7332 (Minchin et al. 2010). VLA moment 0 map of AGES J , overlaid on a B-band DSS image. This galaxy has a high HI mass of 3.1 × M ☉, an HI mass to light ratio of 2 M ☉ /L ☉, and a star formation rate (from FIR and L-band continuum) of ~30 M ☉ /year. From the disturbed HI, this looks to be a post-merger starburst system (Minchin et al. 2010). The Baryon Cycle – Gas into Stars The Baryon Cycle – Intergalactic Gas Transfer The HI Mass Function – The Field Mass Function The HI Mass Function – Environmental Effects The number of HI-rich dwarf galaxies in low-density environments appears to be low (see table). So far, only three such regions have been studied, but it seems likely that the pattern will be repeated in the fields still to be covered. It appears that low density regions have flat or declining faint-end slopes to their HIMFs. FieldEnvironmentNo. Dwarf Galaxies NGC 1156Isolated Galaxy1 UGC 2082Isolated Galaxy1 NGC 7332Galaxy Pair2 As seen in the HIMF (below left), the Abell 1367 HIMF is consistent with the field HIMF, but the Virgo Cluster HIMF falls below it, particularly with the down-turn at the faint end (also seen, more marginally, by Davies et al and Gavazzi et al. 2005). This is consistent with Abell 1367 being a less evolved cluster than Virgo. Future AGES In 2011, AGES aims to complete two further fields (the NGC 3193 group and M33 & the Pisces-Perseus cluster), covering 40 sq. deg., Tthe remaining 95 sq. deg. will have a bandpass limit of z~0.15 rather than the current z~0.06. Fields yet to be covered include the Leo I group, the Local Void, and the outer regions of Abell 1367 along with a selection of isolated galaxies and galaxy pairs. In the longer term, the AO40 phased array feed will offer survey speeds ~4 times faster than ALFA, competitive with SKA pathfinder instruments. This could be used to extend AGES in two ways. Super AGES: Extend the survey to take in wider areas of nearby environments (such as Virgo and Leo I) and go deeper in more distant cluster (such as Abell 1367). This would cover similar physical areas to a similar mass limit in each environment, allowing more direct comparisons to be made. Virgo Deep: Carry out a deeper survey of a similar area of the Virgo Cluster to that already covered by AGES. Both of these would take ~1000 hours with AO40, adding up to a similar total time to the current AGES.