Browsing by Author "Gronwall, C."

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    CONSTRAINING THE Lyα ESCAPE FRACTION WITH FAR- INFRARED OBSERVATIONS OF Lyα EMITTERS
    (2014) Wardlow, Julie L.; Malhotra, S.; Zheng, Z.; Finkelstein, S.; Bock, J.; Bridge, C.; Calanog, J.; Ciardullo, R.; Conley, A.; Cooray, A.; Farrah, D.; Gawiser, E.; Gronwall, C.; Heinis, S.; Ibar, E.; Ivison, R. J.; Marsden, G.; Oliver, S. J.; Rhoads, J.; Riechers, D.; Schulz, B.; Smith, A. J.; Viero, M.; Wang, L.; Zemcov, M.
    We study the far-infrared properties of 498 Ly alpha emitters (LAEs) at z = 2.8, 3.1, and 4.5 in the Extended Chandra Deep Field-South, using 250, 350, and 500 mu m data from the Herschel Multi-tiered Extragalactic Survey and 870 mu m data from the LABOCA ECDFS Submillimeter Survey. None of the 126, 280, or 92 LAEs at z = 2.8, 3.1, and 4.5, respectively, are individually detected in the far-infrared data. We use stacking to probe the average emission to deeper flux limits, reaching 1 sigma depths of similar to 0.1 to 0.4 mJy. The LAEs are also undetected at >= 3 sigma in the stacks, although a 2.5 sigma signal is observed at 870 mu m for the z = 2.8 sources. We consider a wide range of far-infrared spectral energy distributions (SEDs), including an M82 and an Sd galaxy template, to determine upper limits on the far-infrared luminosities and far-infrared-derived star formation rates of the LAEs. These star formation rates are then combined with those inferred from the Ly alpha and UV emission to determine lower limits on the LAEs' Lya escape fraction (f(esc)(Ly alpha)). For the Sd SED template, the inferred LAEs fesc(Ly alpha) are greater than or similar to 30% (1 sigma) at z = 2.8, 3.1, and 4.5, which are all significantly higher than the global fesc(Ly alpha) at these redshifts. Thus, if the LAEs fesc(Ly alpha) follows the global evolution, then they have warmer far-infrared SEDs than the Sd galaxy template. The average and M82 SEDs produce lower limits on the LAE fesc(Ly alpha) of similar to 10%-20% (1 sigma), all of which are slightly higher than the global evolution of fesc(Ly alpha), but consistent with it at the 2 sigma-3 sigma level.
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    Hubble Space Telescope ACS Multiband Coronagraphic Imaging of the Debris Disk around β Pictoris
    (2006) Golimowski, D. A.; Ardila, D. R.; Krist, J. E.; Clampin, M.; Ford, H. C.; Illingworth, G. D.; Bartko, F.; Benitez, N.; Blakeslee, J. P.; Bouwens, R. J.; Bradley, L. D.; Broadhurst, T. J.; Brown, R. A.; Burrows, C. J.; Cheng, E. S.; Cross, N. J. G.; Demarco, R.; Feldman, P. D.; Franx, M.; Goto, T.; Gronwall, C.; Hartig, G. F.; Holden, B. P.; Homeier, N. L.; Infante, L.; Jee, M. J.; Kimble, R. A.; Lesser, M. P.; Martel, A. R.; Mei, S.; Menanteau, F.; Meurer, G. R.; Miley, G. K.; Motta, V.; Postman, M.; Rosati, P.; Sirianni, M.; Sparks, W. B.; Tran, H. D.; Tsvetanov, Z. I.; White, R. L.; Zheng, W.; Zirm, A. W.
    We present F435W(B), F606W (broad V), and F814W(broad I) coronagraphic images of the debris disk around beta Pictoris obtained with the Hubble Space Telescope's Advanced Camera for Surveys. These images provide the most photometrically accurate and morphologically detailed views of the disk between 30 and 300 AU from the star ever recorded in scattered light. We confirm that the previously reported warp in the inner disk is a distinct secondary disk inclined by similar to 5 degrees from the main disk. The projected spine of the secondary disk coincides with the isophotal inflections, or "butterfly asymmetry,'' previously seen at large distances from the star. We also confirm that the opposing extensions of the main disk have different position angles, but we find that this "wing-tilt asymmetry'' is centered on the star rather than offset from it, as previously reported. The main disk's northeast extension is linear from 80 to 250 AU, but the southwest extension is distinctly bowed with an amplitude of similar to 1 AU over the same region. Both extensions of the secondary disk appear linear, but not collinear, from 80 to 150 AU. Within similar to 120 AU of the star, the main disk is similar to 50% thinner than previously reported. The surface brightness profiles along the spine of the main disk are fitted with four distinct radial power laws between 40 and 250 AU, while those of the secondary disk between 80 and 150 AU are fitted with single power laws. These discrepancies suggest that the two disks have different grain compositions or size distributions. The F606W/F435W and F814W/F435W flux ratios of the composite disk are nonuniform and asymmetric about both projected axes of the disk. The disk's northwest region appears 20%-30% redder than its southeast region, which is inconsistent with the notion that forward scattering from the nearer northwest side of the disk should diminish with increasing wavelength. Within similar to 120 AU, the m(F435W)-m(F606W) and m(F435W)-m(F814W) colors along the spine of the main disk are similar to 10% and similar to 20% redder, respectively, than those of beta Pic. These colors increasingly redden beyond similar to 120 AU, becoming 25% and 40% redder, respectively, than the star at 250 AU. These measurements overrule previous determinations that the disk is composed of neutrally scattering grains. The change in color gradient at similar to 120 AU nearly coincides with the prominent inflection in the surface brightness profile at similar to 115 AU and the expected water-ice sublimation boundary. We compare the observed red colors within similar to 120 AU with the simulated colors of nonicy grains having a radial number density alpha r(-3) and different compositions, porosities, and minimum grain sizes. The observed colors are consistent with those of compact or moderately porous grains of astronomical silicate and/or graphite with sizes greater than or similar to 0.15-0.20 mu m, but the colors are inconsistent with the blue colors expected from grains with porosities greater than or similar to 90%. The increasingly red colors beyond the ice sublimation zone may indicate the condensation of icy mantles on the refractory grains, or they may reflect an increasing minimum grain size caused by the cessation of cometary activity.
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    Lyα Emission-Line Galaxies at z = 3.1 in the Extended Chandra Deep Field-South.
    (2007) Gronwall, C.; Infante Lira, Leopoldo; Orsi Moyano, Alvaro; Treister, Ezequiel; Ciardullo, Robin; Hickey, Thomas; Gawiser, Eric; Feldmeier, John J.; van Dokkum, Pieter G.; Urry, C. Megan; Herrera, David
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    Searching for neutral hydrogen halos around z ~ 2.1 and z ~ 3.1 Lya emitting galaxies
    (2013) Feldmeier, J.; Hagen, A.; Gronwall, C.; Gawiser, E.; Guaita, L.; Hagen, L.; Bond, N.; Orsi Moyano, Alvaro