Chapman, Scott
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Item Open Access The next generation virgo cluster survey (NGVS). I. Introduction to the survey(2012) Ferrarese, L.; Cote, P.; Cuillandre, J. -C; Gwyn, S. D. J.; Peng, E. W.; MacArthur, L. A.; Duc, P. -A; Boselli, A.; Mei, S.; Erben, T.; McConnachie, A. W.; Durrell, P. R.; Mihos, J. C.; Jordan, A.; Lancon, A.; Puzia, T. H.; Emsellem, E.; Balogh, M. L.; Blakeslee, J. P.; van Waebeke, L.; Gavazzi, R.; Vollmer, B.; Kavelaars, J. J.; Woods, D.; Ball, N. M.; Boissier, S.; Courteau, S.; Ferriere, E.; Gavazzi, G.; Hildebrandt, H.; Hudelot, P.; Huertas-Company, M.; Liu, C.; McLaughlin, D.; Mellier, Y.; Milkeraitis, M.; Schade, D.; Balkowski, C.; Bournaud, F.; Carlberg, R. G.; Chapman, S. C.; Hoekstra, H.; Peng, C.; Sawicki, M.; Simard, L.; Taylor, J. E.; Tully, R. B.; van Driel, W.; Wilson, C. D.; Burdullis, T.; Mahoney, B.; Manset, N.No abstract available.Item Open Access INFRARED SPECTROGRAPH SPECTROSCOPY AND MULTI-WAVELENGTH STUDY OF LUMINOUS STAR-FORMING GALAXIES AT z 1.9(Published by the University of Chicago Press for the American Astronomical Society., 2009) Huang, J.-S., Faber, S. M., Daddi, E., Laird, E. S., Lai, K., Omont, A., Wu, Y., Younger, J. D., Bundy, K., Cattaneo, A., Chapman, S. C., Conselice, C. J., Dickinson, M., Egami, E., Fazio, G. G., Im, M., Koo, D., Le Floc'h, E., Papovich, C., Rigopoulou, D., Smail, I., Song, M., Van de Werf, P. P., Webb, T. M. A., Willmer, C. N. A., Willner, S. P.,Yan, L.,No abstract available.Item Open Access The Hubble Deep Field North SCUBA Super-map - I. Submillimetre maps, sources and number counts(Blackwell Publishing, 2003) Borys, Colin, Chapman, Scott, Halpern, Mark,Scott, Douglas,We investigate the emission of submillimetre-wave radiation from galaxies in a 165 arcmin2 region surrounding the Hubble Deep Field North. The data were obtained from dedicated observing runs from our group and others using the SCUBA camera on the James Clerk Maxwell Telescope (JCMT), and combined using techniques specifically developed for low signal-to-noise ratio source recovery. The resulting ‘Super-map’ is derived from approximately 60 shifts of JCMT time, taken in a variety of observing modes and chopping strategies, and combined here for the first time. At 850 μm we detect 19 sources at >4σ, including five not previously reported. We also list an additional 15 sources between 3.5 and 4.0σ (where two are expected by chance). The 450-μm map contains five sources at >4σ. We present a new estimate of the 850- and 450-μm source counts. The number of submillimetre galaxies we detect account for approximately 40 per cent of the 850-μm submillimetre background, and we show that mild extrapolations can reproduce it entirely. A clustering analysis fails to detect any significant signal in this sample of SCUBA-detected objects. A companion paper describes the multiwavelength properties of the sources.Item Open Access THE LARGE APEX BOLOMETER CAMERA SURVEY OF THE EXTENDED CHANDRA DEEP FIELD SOUTH(Published by the University of Chicago Press for the American Astronomical Society., 2009) Wei, A.; Kovacs, A.; Coppin, K.; Greve, T.R.; Walter, F.; Smail, Ian; Dunlop, J.S.; Knudsen, K.K.; Alexander, D.M.; Bertoldi, F.; Brandt, W.N.; Chapman, S.C.; Cox, P.; Dannerbauer, H.; De Breuck, C.; Gawiser, E.; Ivison, R.J.; Lutz, D.; Menten, K.M.; Koekemoer, A.M.; Kreysa, E.; Kurczynski, P.; Rix, H.-W.; Schinnerer, E.; van der Werf, P.P.No abstract available.Item Open Access The nature and origin of substructure in the outskirts of M31. I. Surveying the stellar content with the hubble space telescope advanced camera for surveys(2008) Richardson J.C., Ferguson A.M.N., Johnson R.A., Irwin M.J., Faria D.C., Chapman S.C., Tanvir N.R., Ibata R.A., Johnston K.V., Lewis G.F.,McConnachie A.W.,No abstract available.Item Open Access The SCUBA Half Degree Extragalactic Survey (SHADES) - IX. The environment, mass and redshift dependence of star formation(Blackwell Publishing, 2008) Serjeant, S., Dye, S., Mortier, A., Peacock, J., Egami, E., Cirasuolo, M., Rieke, G., Borys, C., Chapman, S., Clements, D., Coppin, K., Dunlop, J., Eales, S., Farrah, D., Halpern, M., Mauskopf, P., Pope, A., Rowan-Robinson, M., Scott, D., Smail, I.,Vaccari, M.,We present a comparison between the SCUBA (Submillimetre Common User Bolometer Array) Half Degree Extragalactic Survey (SHADES) at 450 and 850 in the Lockman Hole East with a deep Spitzer Space Telescope survey at 3.6 conducted in guaranteed time. Using stacking analyses we demonstrate a striking correspondence between the galaxies contributing the submm extragalactic background light, with those likely to dominate the backgrounds at Spitzer wavelengths. Using a combination BRIzK plus Spitzer photometric redshifts, we show that at least a third of the Spitzer-identified submm galaxies at 1 appear to reside in overdensities when the density field is smoothed at 0.5-2 Mpc comoving diameters, supporting the high-redshift reversal of the local star formation-galaxy density relation. We derive the dust-shrouded cosmic star formation history of galaxies as a function of assembled stellar masses. For model stellar masses <, this peaks at lower redshifts than the ostensible z maximum for submm point sources, adding to the growing consensus for ‘downsizing’ in star formation. Our surveys are also consistent with ‘downsizing’ in mass assembly. Both the mean star formation rates ⟨ and specific star formation rates ⟨ are in striking disagreement with some semi-analytic predictions from the Millenium Simulation. The discrepancy could either be resolved with a top-heavy initial mass function, or a significant component of the submm flux heated by the interstellar radiation field.Item Open Access The SCUBA Half-Degree Extragalactic Survey - I. Survey motivation, design and data processing(Blackwell Publishing, 2005) Mortier, A. M. J., Serjeant, S., Dunlop, J. S., Scott, S. E., Ade, P., Alexander, D., Almaini, O., Aretxaga, I., Baugh, C., Benson, A. J., Best, P. N., Blain, A., Bock, J., Borys, C., Bressan, A., Carilli, C., Chapin, E. L., Chapman, S., Clements, D. L., Coppin, K., Crawford, M., Devlin, M., Dicker, S., Dunne, L., Eales, S. A., Edge, A. C., Farrah, D., Fox, M., Frenk, C., Gaztañaga, E., Gear, W. K., Gonzales-Solares, E., Granato, G. L., Greve, T. R., Grimes, J. A., Gundersen, J., Halpern, M., Hargrave, P., Hughes, D. H., Ivison, R. J., Jarvis, M. J., Jenness, T., Jimenez, R., van Kampen, E., King, A., Lacey, C., Lawrence, A., Lepage, K., Mann, R. G., Marsden, G., Mauskopf, P., Netterfield, B., Oliver, S., Olmi, L., Page, M. J., Peacock, J. A., Pearson, C. P., Percival, W. J., Pope, A., Priddey, R. S., Rawlings, S., Roche, N., Rowan-Robinson, M., Scott, D., Sekiguchi, K., Seigar, M., Silva, L., Simpson, C., Smail, I., Stevens, J. A., Takagi, T., Tucker, G., Vlahakis, C., Waddington, I., Wagg, J., Watson, M., Willott, C.,Vaccari, M.,The Submillimetre Common-User Bolometer Array (SCUBA) Half-Degree Extragalactic Survey (SHADES) is a major new blank-field extragalactic submillimetre (submm) survey currently underway at the James Clerk Maxwell Telescope (JCMT). Ultimately, SHADES aims to cover half a square degree at 450 and 850 μm to a 4σ depth of similar 8 mJy at 850 μm. Two fields are being observed, the Subaru/XMM-Newton Deep Field (SXDF) (02 and the Lockman Hole East (10. The survey has three main aims: (i) to investigate the population of high-redshift submm galaxies and the cosmic history of massive dust-enshrouded star formation activity; (ii) to investigate the clustering properties of submm-selected galaxies in order to determine whether these objects could be progenitors of present-day massive ellipticals; and (iii) to investigate the fraction of submm-selected sources that harbour active galactic nuclei. To achieve these aims requires that the submm data be combined with co-spatial information spanning the radio-to-X-ray frequency range. Accordingly, SHADES has been designed to benefit from ultra-deep radio imaging obtained with the Very Large Array (VLA), deep mid-infrared observations from the Spitzer Space Telescope, submm mapping by the Balloon-borne Large Aperture Submillimetre Telescope (BLAST), deep near-infrared imaging with the United Kingdom Infrared Telescope, deep optical imaging with the Subaru Telescope and deep X-ray observations with the XMM-Newton observatory. It is expected that the resulting extensive multiwavelength data set will provide complete photometric redshift information accurate to as well as detailed spectral energy distributions for the vast majority of the submm-selected sources. In this paper, the first of a series on SHADES, we present an overview of the motivation for the survey, describe the SHADES survey strategy, provide a detailed description of the primary data-analysis pipeline and demonstrate the superiority of our adopted matched-filter source-extraction technique over, for example, Emerson-II style methods. We also report on the progress of the survey. As of 2004 February, 720 arcmin2 had been mapped with SCUBA (about 40 per cent of the anticipated final total area) to a median 1σ depth of 2.2 mJy per beam at 850 μm (25 mJy per beam at 450 μm), and the source-extraction routines give a source density of 650 sources deg at 850 μm. Although uncorrected for Eddington bias, this source density is more than sufficient for providing enough sources to answer the science goals of SHADES, once half a square degree is observed. A refined reanalysis of the original 8-mJy survey Lockman hole data was carried out in order to evaluate the new data-reduction pipeline. Of the 17 most secure sources in the original sample, 12 have been reconfirmed, including 10 of the 11 for which radio identifications were previously secured.Item Open Access A Mid-Infrared Imaging Survey of Submillimeter-Selected Galaxies with the Spitzer Space Telescope(2009) Laura J. Hainline, A. W. Blain, Ian Smail, D. T. Frayer, S. C. Chapman, R. J. Ivison,D.M.Alexander,We present Spitzer-IRAC and MIPS mid-IR observations of a sample of 73 radio-detected submillimeter-selected galaxies (SMGs) with spectroscopic redshifts, the largest such sample published to date. From our data, we find that IRAC colors of SMGs are much more uniform as compared with rest-frame UV and optical colors, and z>1.5 SMGs tend to be redder in their mid-IR colors than both field galaxies and lower-z SMGs. However, the IRAC colors of the SMGs overlap those of field galaxies sufficiently that color-magnitude and color-color selection criteria suggested in the literature to identify SMG counterparts produce ambiguous counterparts within an 8'' radius in 20%-35% of cases. We use a rest-frame J-H versus H-K color-color diagram and a S 24/S 8.0 versus S 8.0/S 4.5 color-color diagram to determine that 13%-19% of our sample are likely to contain active galactic nuclei which dominate their mid-IR emission. We observe in the rest-frame JHK colors of our sample that the rest-frame near-IR emission of SMGs does not resemble that of the compact nuclear starburst observed in local ultraluminous IR galaxies and is consistent with more widely distributed star formation. We take advantage of the fact that many high-z galaxy populations selected at different wavelengths are detected by Spitzer to carry out a brief comparison of mid-IR properties of SMGs to UV-selected high-z galaxies, 24 μm-selected galaxies, and high-z radio galaxies, and find that SMGs have mid-IR fluxes and colors which are consistent with being more massive and more reddened than UV-selected galaxies, while the IRAC colors of SMGs are most similar to powerful high-z radio galaxies.Item Open Access Understanding the nature of the optically faint radio sources and their connection to the submillimeter population(2002-05-10) Chapman, Scott C.; Lewis, Geraint F.; Scott, Douglas; Borys, Colin; Richards, Eric A.We present a sample of 43 submillimeter sources detected (at >3 sigma), drawn from our program to follow-up optically faint radio sources with SCUBA. These sources already have associated radio and in many cases optical identifications, and many are also detected at 450 microns. We compare these with 12 submillimeter sources drawn from the literature, which were discovered in blank field mapping campaigns, but also have radio detections. We then use this total sample (55 sources) to study and model the evolution of dusty galaxies. A correlation is observed in the sub-mm/radio color-magnitude diagram, which can be modeled by strong luminosity evolution. The selection effects of the radio/optical pre-selection technique are determined from the models, and a corrected redshift distribution is constrained using a range of model assumptions. The temperature/redshift effects on the 450 microns detected subset of our sample are studied in relation to the models, and prospects for improved measurements in the shorter sub-mm wavelength windows (450 microns and 350 microns) are explored.Item Open Access A Keck/DEIMOS Kinematic Study of Andromeda IX: dark matter on the smallest galactic scales(2005-10-20) Chapman, Scott C.; Ibata, Rodrigo; Lewis, Geraint F.; Ferguson, Annette M. N.; Irwin, Mike; McConnachie, Alan; Tanvir, NialWe present the results of a kinematic survey of the dwarf spheroidal satellite of M31, And-IX, which appears to be the lowest surface brightness and also the faintest galaxy (M_V = -8.3) found to date. Using Keck/DEIMOS spectroscopic data, we have measured its velocity relative to M31, its velocity dispersion, and its metallicity. It exhibits a significant velocity dispersion sigma_v = 6.8+3.0-2.0km/s, which coupled with the low luminosity implies a very high mass to V-band light ratio, M/L ~ 93+120-50msun/lsun (M/L > 17msun/lsun at 99% confidence). Unless strong tidal forces have perturbed this system, this smallest of galaxies is a highly dark matter dominated system.Item Open Access Near-IR adaptive optics imaging of nuclear spiral structure in the Seyfert galaxy, NGC3227(2002-04-04) Chapman, Scott C.; Morris, Simon L.; Walker, Gordon A. H.We present high spatial resolution, near-IR images in J, H, K of the nucleus of NGC3227, obtained with the Adaptive Optics bonnette on CFHT. The ~0.15 arcsec (17pc) resolution allows structures to be probed in the core region. Dust obscuration becomes significantly less pronounced at longer wavelengths, revealing the true geometry of the core region. We are able to identify two main features in our maps: (i) a spiraling association of knots with a counterpart in an HST F606W image; (ii) a smaller scale annulus, orthogonal to the spiral of knots. These features may provide a means to transport material inwards to fuel the active nucleus.Item Open Access Adaptive optics near-IR imaging of NGC2992 - unveiling core structures related to radio figure-8 loops(2000-05-11) Chapman, Scott C.; Morris, Simon L.; Alonso-Herrero, Almudena; Falcke, HeinoWe present near-IR adaptive optics, VLA radio and HST optical imaging of the nearby Seyfert galaxy NGC2992. Spiral structure and an extension to the West are traced down to the core region at the limiting resolution of our near-IR images. A faint, diffuse loop of near-IR and radio emission is also observed to the north, embedded within the prominent 2 arcsec radio loop previously observed to the northwest. Near-IR color maps, and CO narrowband imaging, are then used to identify which regions may not be purely reddened stellar populations. Our new data provide evidence that the VLA radio-loop morphology in the shape of a figure-8 represents two components superimposed: 1) outflow bubbles out of the plane of the disk, coincident with the extended emission line region (EELR); 2) star formation along the spiral arm within the galaxy disk and through the dust lane. The near-IR continuum emission associated with the outflowing radio bubbles suggest that the radio loops are driven by the active nucleus.Item Open Access Submillimetre sources in rich cluster fields - source counts, redshift estimates, and cooling flow limits(2002-02-11) Chapman, Scott C.; Scott, Douglas; Borys, Colin; Fahlman, Gregory G.Recent submillimetre surveys have revealed a population of dusty, high redshift sources of great cosmological significance for understanding dust-enshrouded star formation in distant galaxies, and for determining the origin of the far-IR background. In this paper, we analyze nine rich cluster fields mapped at 850 and 450 microns with the SCUBA array on the James Clerk Maxwell telescope. Lensing models of the clusters are developed in order to derive accurate source counts for our sample. VLA maps of the same clusters are used to help constrain the redshift distribution of our SCUBA detections. Implications for high redshift galaxies and for the far-IR background are discussed. We also provide limits on distributed dust produced by cooling flows in these clusters.Item Open Access The Far- and Mid-Infrared/Radio Correlations in the Spitzer Extragalactic First Look Survey(2004-09) Appleton, P. N.; Fadda, D. T.; Marleau, F. R.; Frayer, D. T.; Helou, G.; Condon, J. J.; Choi, P. I.; Yan, L.; Lacy, M.; Wilson, G.; Armus, L.; Chapman, S. C.; Fang, F.; Heinrichson, I.; Im, M.; Jannuzi, B. T.; Storrie-Lombarsi, L. J.; Shupe, D.; Soifer, B. T.; Squires, G.; Teplitz, H. I.Using the SPITZER SPACE TELESCOPE and the VLA, we present the first DIRECT evidence that the well-known far-infrared/radio correlation is valid to cosmologically significant redshift. We also confirm, with improved statistics compared with previous surveys, a similar result for the Mid-IR/radio correlation. We explore the dependence of monochromatic q_{24} and q_{70} on z. The results were obtained by matching Spitzer sources at 24 and 70 microns with VLA 1.4 GHz micro-Jy radio sources obtained for the SPITZER FLS. Spectroscopic redshifts have been obtained for over 500 matched IR/radio sources using observations at WIYN, Keck and archival SDSS data extending out to z > 2. We find that q_{24} shows significantly more dispersion than q_{70}. By comparing the observed fluxes at 70, 24 and 4.5 microns with a library of SED templates, we find that the larger dispersion in q_{24} is predictable in terms of systematic variations in SED shape throughout the population. Although the models are not able to encompass the full range of observed behavior (both the presence of either extremely flat or extremely steep IR SEDs), the fitting parameters were used to `k-correct' the higher-z galaxies which resulted in a reduced scatter in q. For comparison, we also corrected these data using the SED for M82. The results for 24 and 70 microns provide strong consistent evidence for the universality of the mid-IR/radio and far-IR/radio correlations out to redshifts of at least z = 1.Item Open Access A search for the submillimetre counterparts to Lyman break galaxies(2002-04-04) Chapman, Scott C.; Scott, Douglas; Steidel, Charles C.; Borys, Colin; Halpern, Mark; Morris, Simon L.; Adelberger, Kurt L.; Dickinson, Mark; Giavalisco, Mauro; Pettini, MaxWe have carried out targetted sub-mm observations as part of a programme to explore the connection between the rest-frame UV and far-IR properties of star-forming galaxies at high redshift, which is currently poorly understood. On the one hand the Lyman break technique is very effective at selecting z~3 galaxies. On the other hand `blank field' imaging in the sub-mm seems to turn up sources routinely, amongst which some are star forming galaxies at similar redshifts. Already much work has been done searching for optical identifications of objects detected using the SCUBA instrument. Here we have taken the opposite approach, performing sub-mm photometry for a sample of Lyman break galaxies whose UV properties imply high star formation rates. The total signal from our Lyman break sample is undetected in the sub-mm, at an RMS level of 0.5 mJy, which implies that the population of Lyman break galaxies does not constitute a large part of the recently detected blank-field sub-mm sources. However, our one detection suggests that with reasonable SCUBA integrations we might expect to detect those few LBGs that are far-IR brightest.Item Open Access Search For Trapped Antihydrogen(2011-1/2011) Andresen, Gorm B.; Ashkezari, Mohammad D.; Baquero-Ruiz, Marcelo; Bertsche, William; Bowe, Paul D.; Bray, Crystal C.; Butler, Eoin; Cesar, Claudio L.; Chapman, Steven; Charlton, Michael; Fajans, Joel; Friesen, Tim; Fujiwara, Makoto C.; Gill, David R.; Hangst, Jeffrey S.; Hardy, Walter N.; Hayano, Ryugo S.; Hayden, Michael E.; Humphries, Andrew J.; Hydomako, Richard; Jonsell, Svante; J\orgensen, Lars V.; Kurchaninov, Lenoid; Lambo, Ricardo; Madsen, Niels; Menary, Scott; Nolan, Paul; Olchanski, Konstantin; Olin, Art; Povilus, Alexander; Pusa, Petteri; Robicheaux, Francis; Sarid, Eli; Nasr, Sarah Seif El; Silveira, Daniel M.; So, Chukman; Storey, James W.; Thompson, Robert I.; van der Werf, Dirk P.; Wilding, Dean; Wurtele, Jonathan S.; Yamazaki, YasunoriWe present the results of an experiment to search for trapped antihydrogen atoms with the ALPHA antihydrogen trap at the CERN Antiproton Decelerator. Sensitive diagnostics of the temperatures, sizes, and densities of the trapped antiproton and positron plasmas have been developed, which in turn permitted development of techniques to precisely and reproducibly control the initial experimental parameters. The use of a position-sensitive annihilation vertex detector, together with the capability of controllably quenching the superconducting magnetic minimum trap, enabled us to carry out a high-sensitivity and low-background search for trapped synthesised antihydrogen atoms. We aim to identify the annihilations of antihydrogen atoms held for at least 130 ms in the trap before being released over ~30 ms. After a three-week experimental run in 2009 involving mixing of 10^7 antiprotons with 1.3 10^9 positrons to produce 6 10^5 antihydrogen atoms, we have identified six antiproton annihilation events that are consistent with the release of trapped antihydrogen. The cosmic ray background, estimated to contribute 0.14 counts, is incompatible with this observation at a significance of 5.6 sigma. Extensive simulations predict that an alternative source of annihilations, the escape of mirror-trapped antiprotons, is highly unlikely, though this possibility has not yet been ruled out experimentally.Item Open Access Submillimetre Detection of the z=2.83 Lyman-Break Galaxy, Westphal-MM8, and Implications for SCUBA2(2009-03-12) Chapman, Scott C.; Casey, Caitlin M.We present confusion limited submillimetre (submm) observations with the SCUBA camera on the JCMT of the z=2.83 Lyman-break galaxy (LBG), Westphal-MM8, reaching an 850um sensitivity even greater than that achieved in the SCUBA map of the Hubble Deep Field region. The detection of Westphal-MM8 (S_{850um} = 1.98+-0.48mJy), along with the literature submm detections of lensed LBGs, suggest that the LBG population may contribute significantly to the source counts of submm selected galaxies in the 1-2mJy regime. Additionally, submm-luminous LBGs are a viable progenitor population for the recently discovered evolved galaxies at z~2-2.5. These observations represent an important baseline for SCUBA2 observations which will regularly map large regions of the sky to this depth.Item Open Access B1933+503, a dusty radio quasar at z>2: implications for blank field sub-mm surveys?(1998-10-27) Chapman, Scott C.; Scott, Douglas; Lewis, Geraint F.; Borys, Colin; Fahlman, Gregory G.We present a detailed mm-wave and optical study of the gravitational lens system B1933+503, discovered by Sykes et al.(1998) in the radio. This object is probably the most complex lens system known, with 10 lensed components within a radius of one arcsecond. It is potentially important as a probe of the Hubble constant, although no optical counterpart has thus far been observed down to I=24.2. We have obtained new sub-millimetre detections at 450, 850 and 1350 microns. We have also constrained the possible dust emission from the proposed foreground lensing galaxy using a K-band adaptive optics image and CO(5-4) measurements. A lensing model is constructed, taking the foreground elliptical galaxy at z=0.755 as the lensing mass. From this we derive a scenario from which to model the sub-millimetre emission. Several arguments then point to the source in the B1933+503 system lying above a redshift of 2. We speculate that unlensed relatives of this source may constitute a sizable fraction of the 850 micron source counts.Item Open Access Further multiwavelength observations of the SSA22 Ly_alpha emitting `blob'(2004-05) Chapman, S. C.; Scott, D.; Windhorst, R. A.; Frayer, D. T.; Borys, C.; Lewis, G. F.; Ivison, R. J.We present new follow-up observations of the sub-mm luminous Ly_alpha-emitting object in the SSA22 z=3.09 galaxy overdensity, referred to as `Blob 1' by Steidel et al.(2000). In particular we discuss high resolution Hubble Space Telescope optical imaging, Owens Valley Radio Observatory spectral imaging, Keck spectroscopy, VLA 20cm radio continuum imaging, and Chandra X-ray observations. We also present a more complete analysis of the existing James Clerk Maxwell Telescope sub-mm data. We detect several optical continuum components which may be associated with the core of the submillimeter emitting region. A radio source at the position of one of the HST components (22:17:25.94, +00:12:38.9) identifies it as the likely counterpart to the submillimeter source. We also tentatively detect the CO(4-3) molecular line, centered on the radio position. We use the CO(4-3) intensity to estimate a limit on the gas mass for the system. The optical morphology of sources within the Ly_alpha cloud appears to be filamentary, while the optical source identified with the radio source has a dense knot which may be an AGN or compact starburst. We obtain a Keck-LRIS spectrum of this object, despite its faintness (R=26.8). The spectrum reveals weak Ly_alpha emission, but no other obvious features, suggesting that the source is not an energetic AGN (or that it is extremely obscured). We use non-detections in deep Chandra X-ray images to constrain the nature of the `Blob'. Although conclusive evidence regarding the nature of the object remains hard to obtain at this redshift, the evidence presented here is at least consistent with a dust-obscured AGN surrounded by a starburst situated at the heart of this giant Ly_alpha cloud.Item Open Access Strangers in the night: Discovery of a dwarf spheroidal galaxy on its first Local Group infall(2007-06-20) Chapman, S. C.; Penarrubia, J.; Ibata, R.; McConnachie, A.; Martin, N.; Irwin, M.; Blain, A.; Lewis, G. F.; Letarte, B.; Lo, K.; Ludlow, A.; O'neil, K.We present spectroscopic observations of the AndXII dwarf spheroidal galaxy using DEIMOS/Keck-II, showing it to be moving rapidly through the Local Group (-556 km/s heliocentric velocity, -281 km/s relative to Andromeda from the MW), falling into the Local Group from ~115 kpc beyond Andromeda's nucleus. AndXII therefore represents a dwarf galaxy plausibly falling into the Local Group for the first time, and never having experienced a dense galactic environment. From Green Bank Telescope observations, a limit on the H{I} gas mass of <3000 Msun suggests that AndXII's gas could have been removed prior to experiencing the tides of the Local Group galaxies. Orbit models suggest the dwarf is close to the escape velocity of M31 for published mass models. AndXII is our best direct evidence for the late infall of satellite galaxies, a prediction of cosmological simulations.