FIRST RESULTS FROM THE DRAGONFLY TELEPHOTO ARRAY: THE APPARENT LACK OF A STELLAR HALO IN THE MASSIVE SPIRAL GALAXY M101

(ProQuest: ... denotes formulae and/or non-USASCII text omitted)We use a new telescope concept, the Dragonfly Telephoto Array, to study the low surface brightness outskirts of the spiral galaxy M101. The radial surface brightness profile is measured down to mu sub(g) ~ 32 mag arcsec super(-2), a dep...

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Published inAstrophysical journal. Letters Vol. 782; no. 2; pp. 1 - 6
Main Authors van Dokkum, Pieter G, Abraham, Roberto, Merritt, Allison
Format Journal Article
LanguageEnglish
Published United States 20.02.2014
Subjects
APPROXIMATIONS
Arrays
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
BRIGHTNESS
COLOR
COMPUTERIZED SIMULATION
COSMOLOGY
Density
Disks
Drag (hindrance)
GALACTIC EVOLUTION
Galactic halos
Halos
MASS
Mathematical models
MILKY WAY
Odonata
SATELLITES
SENSITIVITY
STARS
Surface brightness
SURFACES
TELESCOPES
VISIBLE RADIATION
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Summary:(ProQuest: ... denotes formulae and/or non-USASCII text omitted)We use a new telescope concept, the Dragonfly Telephoto Array, to study the low surface brightness outskirts of the spiral galaxy M101. The radial surface brightness profile is measured down to mu sub(g) ~ 32 mag arcsec super(-2), a depth that approaches the sensitivity of star count studies in the Local Group. We convert surface brightness to surface mass density using the radial g - r color profile. The mass density profile shows no significant upturn at large radius and is well-approximated by a simple bulge + disk model out to R = 70 kpc, corresponding to 18 disk scale lengths. Fitting a bulge + disk + halo model we find that the best-fitting halo mass ... The total stellar mass of M101 is ..., and we infer that the halo mass fraction ... This mass fraction is lower than that of the Milky Way ([functionof] sub(halo) ~ 0.02) and M31 ([functionof] sub(halo) ~ 0.04). All three galaxies fall below the [functionof] sub(halo)-M sub(tot,[lo w *]) relation predicted by recent cosmological simulations that trace the light of disrupted satellites, with M101's halo mass a factor of ~10 below the median expectation. However, the predicted scatter in this relation is large, and more galaxies are needed to better quantify this possible tension with galaxy formation models. Dragonfly is well suited for this project: as integrated-light surface brightness is independent of distance, large numbers of galaxies can be studied in a uniform way.
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ISSN:2041-8205
2041-8213
DOI:10.1088/2041-8205/782/2/L24