Browsing by Author "Blakeslee, J. P."

Now showing 1 - 4 of 4
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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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    Specific Frequencies and Luminosity Profiles of Cluster Galaxies and Intracluster Light in Abell 1689
    (IOP PUBLISHING LTD, 2017) Alamo Martinez, K. A.; Blakeslee, J. P.
    We present magnitudes and profile fits for 180 galaxies in the central field of the massive lensing cluster Abell 1689 using very deep imaging with the Hubble Space Telescope Advanced Camera for Surveys in the F814W bandpass. Previous work revealed an exceptionally large number of globular clusters (GCs) in A1689 and mapped their number density distribution. We decompose this number density map into GCs associated with individual cluster galaxies and ICGCs (intracluster GCs) associated with the intracluster light (ICL). In all, we measure GC specific frequencies S-N for 33 cluster members and the ICL. The relation between S-N and galaxy magnitude is consistent with the trend observed in Virgo, although some intermediate-luminosity galaxies scatter to S-N > 10. We estimate that the ICL makes up 11% of the starlight in this field, whereas the ICGCs account for similar to 35% of the GCs, both consistent with predictions from simulations. Galaxies with higher S-N values tend to be rounder, and there is a marginally significant trend of decreasing S-N with increasing specific angular momenta lambda(R). We also reevaluate the GC population in the A2744 Frontier Field, for which fewer than 1/10 as many GCs have been detected because of its larger distance. Finally, our core-Sersic fit to the light profile of the A1689 brightest cluster galaxy implies a break radius of 3.8 kpc, among the largest known; we discuss implications of the sizable core and extensive GC population for the supermassive black hole in light of scaling relations.
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    The Next Generation Virgo Cluster Survey (NGVS). XIV. The Discovery of Low-mass Galaxies and a New Galaxy Catalog in the Core of the Virgo Cluster
    (2020) Ferrarese, L.; Côté, P.; Macarthur, L. A.; Durrell, P. R.; Gwyn, S. D. J.; Duc, P. A.; Sánchez Janssen, R.; Jordán Colzani, Andrés Cristóbal; Puzia, Thomas H.; Santos, M.; Blakeslee, J. P.; Boselli, A.; Boyer, F.; Cantiello, M.; Courteau, S.; Cuillandre, J. C.; Emsellem, E.; Erben, T.; Gavazzi, G.; Guhathakurta, P.; Huertas Company, M.; Lançon, A.; Liu, C.; Mei, S.; Mihos, J. C.; Peng, E. W.; Roediger, J.; Schade, D.; Taylor, J. E.; Toloba, E.; Zhang, H.
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    The Next Generation Virgo Cluster Survey. XXXIV. Ultracompact Dwarf Galaxies in the Virgo Cluster
    (2020) Liu, C. Z.; Cote, P.; Peng, E. W.; Roediger, J.; Zhang, H. X.; Ferrarese, L.; Sánchez Janssen, R.; Guhathakurta, P.; Yang, X. H.; Puzia, Thomas H.; Jing, Y. P.; Alamo Martínez, K.; Blakeslee, J. P.; Boselli, A.; Cuilandre, J. C.; Duc, P. A.; Durrell, P.; Gwyn, S.; Jordán Colzani, Andrés Cristóbal; Ko, Y.; Lancon, A.; Lim, S.; Longobardi, A.; Mei, S.; Mihos, J. C.; Munoz, R.; Powalka, M.; Spengler, C.; Toloba, E.