The DECam Plane Survey is a five-band optical and near-infrared survey of the southern Galactic plane with the Dark Energy Camera at Cerro Tololo. The survey is designed to reach past the ...main-sequence turn-off of old populations at the distance of the Galactic center through a reddening of 1.5 mag. Typical single-exposure depths are 23.7, 22.8, 22.3, 21.9, and 21.0 mag (AB) in the grizY bands, with seeing around . The footprint covers the Galactic plane with , . The survey pipeline simultaneously solves for the positions and fluxes of tens of thousands of sources in each image, delivering positions and fluxes of roughly two billion stars with better than 10 mmag precision. Most of these objects are highly reddened and deep in the Galactic disk, probing the structure and properties of the Milky Way and its interstellar medium. The fully-processed images and derived catalogs are publicly available.
ABSTRACT The dust extinction curve is a critical component of many observational programs and an important diagnostic of the physics of the interstellar medium. Here we present new measurements of ...the dust extinction curve and its variation toward tens of thousands of stars, a hundred-fold larger sample than in existing detailed studies. We use data from the APOGEE spectroscopic survey in combination with ten-band photometry from Pan-STARRS1, the Two Micron All-Sky Survey, and Wide-field Infrared Survey Explorer. We find that the extinction curve in the optical through infrared is well characterized by a one-parameter family of curves described by R(V). The extinction curve is more uniform than suggested in past works, with ( R ( V ) ) = 0.18 , and with less than one percent of sight lines having R ( V ) > 4 . Our data and analysis have revealed two new aspects of Galactic extinction: first, we find significant, wide-area variations in R(V) throughout the Galactic plane. These variations are on scales much larger than individual molecular clouds, indicating that R(V) variations must trace much more than just grain growth in dense molecular environments. Indeed, we find no correlation between R(V) and dust column density up to E ( B − V ) 2 . Second, we discover a strong relationship between R(V) and the far-infrared dust emissivity.
As of 2012 January 21, the Pan-STARRS 1 3pi Survey has observed the 3/4 of the sky visible from Hawaii with a minimum of 2 and mean of 7.6 observations in five filters, g sub(P1), r sub(P1), i ...sub(P1), z sub(P1), y sub(P1). Now at the end of the second year of the mission, we are in a position to make an initial public release of a portion of this unprecedented data set. This article describes the PS1 Photometric Ladder, Release 12.01. This is the first of a series of data releases to be generated as the survey coverage increases and the data analysis improves. The Photometric Ladder has rungs every hour in right ascension and at four intervals in declination. We will release updates with increased area coverage (more rungs) from the latest data set until the PS1 survey and the final re-reduction are completed. The currently released catalog presents photometry of ~ 1000 objects per square degree in the rungs of the ladder. Saturation occurs at g sub(P1), r sub(P1), i sub(P1) ~ 13.5; z sub(P1) ~ 13.0; and y sub(P1) ~ 12.0. Photometry is provided for stars down to g sub(P1), r sub(P1), z sub(P1) ~ 19.1 in the AB system. This data release depends on the rigid "Ubercal" photometric calibration using only the photometric nights, with systematic uncertainties of (8.0, 7.0, 9.0, 10.7, 12.4) mmag in (g sub(P1), r sub(P1), i sub(p1), z sub(P1), y sub(P1)). Areas covered only with lower quality nights are also included, and have been tied to the Ubercal solution via relative photometry; photometric accuracy of the non-photometric regions is lower and should be used with caution.
Near-infrared spectroscopy from APOGEE and wide-field optical photometry from Pan-STARRS1 have recently made precise measurements of the shape of the extinction curve possible for tens of thousands ...of stars, parameterized by R(V). These measurements revealed structures in R(V) with large angular scales, which are challenging to explain in existing dust paradigms. In this work, we combine three-dimensional maps of dust column density with R(V) measurements to constrain the three-dimensional distribution of R(V) in the Milky Way. We find that the variations in R(V) are correlated on kiloparsec scales. In particular, most of the dust within one kiloparsec in the outer Galaxy, including many local molecular clouds (Orion, Taurus, Perseus, California, and Cepheus), has a significantly lower R(V) than more distant dust in the Milky Way. These results provide new input to models of dust evolution and processing, and complicate the application of locally derived extinction curves to more distant regions of the Milky Way and to other galaxies.
Distance measurements to molecular clouds are important but are often made separately for each cloud of interest, employing very different data and techniques. We present a large, homogeneous catalog ...of distances to molecular clouds, most of which are of unprecedented accuracy. We determine distances using optical photometry of stars along lines of sight toward these clouds, obtained from PanSTARRS-1. We simultaneously infer the reddenings and distances to these stars, tracking the full probability distribution function using a technique presented in Green et al. We fit these star-by-star measurements using a simple dust screen model to find the distance to each cloud. We thus estimate the distances to almost all of the clouds in the Magnani et al. catalog, as well as many other well-studied clouds, including Orion, Perseus, Taurus, Cepheus, Polaris, California, and Monoceros R2, avoiding only the inner Galaxy. Typical statistical uncertainties in the distances are 5%, though the systematic uncertainty stemming from the quality of our stellar models is about 10%. The resulting catalog is the largest catalog of accurate, directly measured distances to molecular clouds. Our distance estimates are generally consistent with available distance estimates from the literature, though in some cases the literature estimates are off by a factor of more than two.
Despite more than a century of biological research on the evolution and maintenance of mimetic signals, the relative frequencies of models and mimics necessary to establish and maintain Batesian ...mimicry in natural populations remain understudied. Here we investigate the frequency-dependent dynamics of imperfect Batesian mimicry, using predation experiments involving artificial butterfly models. We use two geographically distinct populations of Adelpha butterflies that vary in their relative frequencies of a putatively defended model (Adelpha iphiclus) and Batesian mimic (Adelpha serpa). We found that in Costa Rica, where both species share similar abundances, Batesian mimicry breaks down, and predators more readily attack artificial butterfly models of the presumed mimic, A. serpa. By contrast, in Ecuador, where A. iphiclus (model) is significantly more abundant than A. serpa (mimic), both species are equally protected from predation. Our results provide compelling experimental evidence that imperfect Batesian mimicry is frequency-dependent on the relative abundance of models and mimics in natural populations, and contribute to the growing body of evidence that complex dynamics, such as seasonality or the availability of alternative prey, influence the evolution of mimetic traits.
Abstract
Turbulence is a key process in many fields of astrophysics. Advances in numerical simulations of fluids over the last several decades have revolutionized our understanding of turbulence and ...related processes such as star formation and cosmic ray propagation. However, data from numerical simulations of astrophysical turbulence are often not made public. We introduce a new simulation-oriented database for the astronomical community: the Catalogue for Astrophysical Turbulence Simulations (CATS), located at
www.mhdturbulence.com
. CATS includes magnetohydrodynamic (MHD) turbulent box simulation data products generated by the public codes
athena++
,
arepo
,
enzo,
and
flash
. CATS also includes several synthetic observational data sets, such as turbulent HI data cubes. We also include measured power spectra and three-point correlation functions from some of these data. We discuss the importance of open-source statistical and visualization tools for the analysis of turbulence simulations such as those found in CATS.
During a survey for stars with disks in the Taurus star-forming region using the Spitzer Space Telescope, we have discovered a pair of young brown dwarfs, FU Tau A and B, in the Barnard 215 dark ...cloud. They have a projected angular separation of 57, corresponding to 800 AU at the distance of Taurus. To assess the nature of these two objects, we have obtained spectra of them and constructed spectral energy distributions. Both sources are young (~1 Myr) according to their H alpha emission, gravity-sensitive spectral features, and mid-infrared excess emission. The proper motion of FU Tau A provides additional evidence of its membership in Taurus. We measure spectral types of M7.25 and M9.25 for FU Tau A and B, respectively, which correspond to masses of ~0.05 and ~0.015 M according to the evolutionary models of Chabrier and Baraffe. FU Tau A is significantly overluminous relative to an isochrone passing through FU Tau B and relative to other members of Taurus near its spectral type, which may indicate that it is an unresolved binary. FU Tau A and B are likely to be components of a binary system based on the low probability (~3 X 10-4) that Taurus would produce two unrelated brown dwarfs with a projected separation of a <= 6''. Barnard 215 contains only one other young star and is in a remote area of Taurus, making FU Tau A and B the first spectroscopically confirmed brown dwarfs discovered forming in isolation rather than in a stellar cluster or aggregate. Because they were born in isolation and comprise a weakly bound binary, dynamical interactions with stars could not have played a role in their formation, and thus are not essential for the birth of brown dwarfs.
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