1801.02634
The Astropy Project: building an inclusive, open-science project and status of the v2.0 software
Price-Whelan, et al
The Astropy project supports and fosters the development of open-source and openly-developed Python packages that provide commonly-needed functionality to the astronomical community. A key element of the Astropy project is the core package Astropy, which serves as the foundation for more specialized projects and packages. In this article, provide and overview of the organization of the Astropy project and summarize key features in the core package as of the recent major release, version 2.0. Then describe the project infrastructure designed to facilitate and support development for a broader ecosystem of inter-operable packages. Conclude with a future outlook of planned new features and directions for the broader Astropy project.
1801.03009
Predicting the binary black hole population of the Milky Way with cosmological simulation
Lamberts, et al
Binary BHs are the primary endpoint of massive stellar evolution. Their properties provide a unique opportunity to constraint binary evolution, which is still poorly understood. In this paper, predict the inventory of binary BHs and their merger products in/around the MW, and detail their main properties. Present the first combination of a high-res cosmo sim of a MW-mass galaxy with a binary population synthesis model. The hydrodynamicsimulation, taken from the FIRE project, provides a cosmologically realistic SFH for the galaxy and its stellar halo and satellites. Apply a metallicity-dependent evolutionary model to the star particles to produce individual binary BHs. Find that a million binary BHs have merged in the model Milky Way, and 3 million binary are still present, with an average mass of 28 Msun per binary. Because the BH progenitors are biased towards low metallicity stars, half reside in the stellar halo and satellites and 40% of the binaries were formed outside the main galaxy. This trend increases with the masses of the BHs. The numbers and mass distribution of the merged systems is compatible with the LIGO/Virgo detections. Observations of these BHs will be challenging, both with EM methods and LISA. Find that a cosmologically realistic SFH, with self-consistent metal enrichment and Galactic accretion history, are key ingredients for determining binary BH rates that can be compared with observations to constrain massive binary evolution.
1801.03103
A candidate $z/sim10$ galaxy strongly lensed into a spatially resolved arc
Salmon, Coe, et al
The most distant galaxies known are at z~10-11, observed 400-500 Myr after the Big Bang. The view z~10-11 candidates discovered to date have been exceptionally small -- barely resolved, if at all, by HST. Here, present the discovery of SPT0615-JD, a fortuitous z~10 (z_poht-9.9±0.6) galaxy candidate stretched into an arc over ~2.5" by the effects of SL. Discovered in the Reionization Lensing Cluster Survey (RELICS) Hubble Treasury program wand companion S-RELICS Spitzer program, this candidate has a lensed H-band magnitude of 25.7±0.1 AB mag. With a magnification of mu~4-7 estimated from the lens models, the de-lensed intrinsic magnitude is 27.6±0.3 AB mag, and the half-light radius is r_e<0.8 kpc, both consistent with other z>9 candidates. The inferred stellar mass [log (M*/Msun)]=9.7^0.7_-0.5 and SFR log [SFR/Msun yr^-1]=1.3+0.2_-0.3 indicate that this candidate is a typical SF galaxy on the z>6 SFR-M* relation. Note that three independent lens models predict two counter images, at least one of which should be of a similar magnitude to the arc, but these counter images are not yet detected. Counterimages would not be expected if the arc were at lower redshift. However, the only spectral energy distributions capable of fitting the Hubble and Spitzer photometry well at lower redshifts require unphysical combinations of z~2 galaxy properties. The unprecedented lensed size of the z~10 candidate offers the potential for the JWST to study the geometric and kinematic properties of a galaxy observed 500 Myr after the Big Bang.
1801.03555
Galactic Reddening in 3D from stellar photometry - An improved map
Green, Schlafly, Finkbeiner, Nix, et al
Present a new 3D map of interstellar dust reddening, covering 3 quarters of the sky (declinations greater than -30 deg) out to a distance of several kilo parsecs. The map is based on high-quality stellar photometry of 800 million stars from Pan-STARRS 1 and 2MASS. Divide the sky into sightlines containing a few hundred stars each, and then infer stellar distances and types, along with the line-of-sight dust distribution. The new map incorporates a more accurate average extinction law and an additional 1.5 years of Pan-STARRS 1 data, tracing dust to greater extinctions and at higher angular resolutions than the previous map. Out of the plane of the Galaxy, the map agrees well with 2D reddening maps derived from FIR dust emission. After accepting for a 15% difference in scale, find a mean scatter of 10% between the map and the Planck FIR emission-based dust map, out to a depth of 0.8 mag in E(r-z), with the level of agreement varying over the sky. The map can be downloaded at http://argonaut.skymaps.info, or by it sDOI: 10.7910/DVN/LCYHJG.
1801.03941
Full-sky ray-tracing simulation of weak lensing using ELUCID simulations: exploring galaxy intrinsic alignment and cosmic shear correlations
Wei, et al
The IA of galaxies is an important systematic effect in WL surveys, which can affect the derived cosmological parameters. One direct way to distinguish different alignment models and quantify their effects on the measurement is to produce mock WL surveys. In this work, use full-sky ray-tracing technique to produce mock images of galaxies from the ELUCID N-body sims run with the WMAP9 cosmology. The model assumes that the shape of central elliptical galaxy follows that of the DM halo, and spiral galaxy follows the halo spin. Using the mock galaxy images, a combination of galaxy intrinsic shape and the gravitational shear, compare the predicted tomographic shear correlation to the results of KiDS and DLS. It is found that the predictions stay between the KiDS and DLS results. Rule out a model in which the satellite galaxies are radially aligned with the center galaxy, otherwise the shear-correlations on small scales are too high. Most importantly, find that although the IA of spiral galaxies is very weak, they induce a positive correlation between the gravitational shear signal and the intrinsic galaxy orientation (GI). This is because the spiral galaxy is tangentially aligned with the nearby large-scale overdensity, contrary to the radial alignment of elliptical galaxy. The results explain the origin of detected positive GI term from the WL surveys. Conclude that in future analysis, the GI model must include the dependence on galaxy types in more detail. And the full-sky mock data introduced in this work can be available if you are interesting. :D
1801.xxxxx
The CosmicWatch desktop muon detector: a self-contained, pocket sized particle detector
Axani, Frankiewicz, Conrad
The CosmicWatch Desktop Muon Detector is a self-contained, hand-held cosmic ray muon detector that is valuable for astro/particle physics research applications and outreach. The material cost of each detector is under $100 and it takes a novice student approximately four hours to build their first detector. The detectors are powered via a USB connection and the data can either be recorded directly to a computer or to a microSD card. Arduino- and Python-based software is provided to operate the detector and an online application to plot the data in real-time. In this paper, describe the various design features, evaluate the performance, and illustrate the detectors capabilities by providing several example measurements.
The Astropy Project: building an inclusive, open-science project and status of the v2.0 software
Price-Whelan, et al
The Astropy project supports and fosters the development of open-source and openly-developed Python packages that provide commonly-needed functionality to the astronomical community. A key element of the Astropy project is the core package Astropy, which serves as the foundation for more specialized projects and packages. In this article, provide and overview of the organization of the Astropy project and summarize key features in the core package as of the recent major release, version 2.0. Then describe the project infrastructure designed to facilitate and support development for a broader ecosystem of inter-operable packages. Conclude with a future outlook of planned new features and directions for the broader Astropy project.
1801.03009
Predicting the binary black hole population of the Milky Way with cosmological simulation
Lamberts, et al
Binary BHs are the primary endpoint of massive stellar evolution. Their properties provide a unique opportunity to constraint binary evolution, which is still poorly understood. In this paper, predict the inventory of binary BHs and their merger products in/around the MW, and detail their main properties. Present the first combination of a high-res cosmo sim of a MW-mass galaxy with a binary population synthesis model. The hydrodynamicsimulation, taken from the FIRE project, provides a cosmologically realistic SFH for the galaxy and its stellar halo and satellites. Apply a metallicity-dependent evolutionary model to the star particles to produce individual binary BHs. Find that a million binary BHs have merged in the model Milky Way, and 3 million binary are still present, with an average mass of 28 Msun per binary. Because the BH progenitors are biased towards low metallicity stars, half reside in the stellar halo and satellites and 40% of the binaries were formed outside the main galaxy. This trend increases with the masses of the BHs. The numbers and mass distribution of the merged systems is compatible with the LIGO/Virgo detections. Observations of these BHs will be challenging, both with EM methods and LISA. Find that a cosmologically realistic SFH, with self-consistent metal enrichment and Galactic accretion history, are key ingredients for determining binary BH rates that can be compared with observations to constrain massive binary evolution.
1801.03103
A candidate $z/sim10$ galaxy strongly lensed into a spatially resolved arc
Salmon, Coe, et al
The most distant galaxies known are at z~10-11, observed 400-500 Myr after the Big Bang. The view z~10-11 candidates discovered to date have been exceptionally small -- barely resolved, if at all, by HST. Here, present the discovery of SPT0615-JD, a fortuitous z~10 (z_poht-9.9±0.6) galaxy candidate stretched into an arc over ~2.5" by the effects of SL. Discovered in the Reionization Lensing Cluster Survey (RELICS) Hubble Treasury program wand companion S-RELICS Spitzer program, this candidate has a lensed H-band magnitude of 25.7±0.1 AB mag. With a magnification of mu~4-7 estimated from the lens models, the de-lensed intrinsic magnitude is 27.6±0.3 AB mag, and the half-light radius is r_e<0.8 kpc, both consistent with other z>9 candidates. The inferred stellar mass [log (M*/Msun)]=9.7^0.7_-0.5 and SFR log [SFR/Msun yr^-1]=1.3+0.2_-0.3 indicate that this candidate is a typical SF galaxy on the z>6 SFR-M* relation. Note that three independent lens models predict two counter images, at least one of which should be of a similar magnitude to the arc, but these counter images are not yet detected. Counterimages would not be expected if the arc were at lower redshift. However, the only spectral energy distributions capable of fitting the Hubble and Spitzer photometry well at lower redshifts require unphysical combinations of z~2 galaxy properties. The unprecedented lensed size of the z~10 candidate offers the potential for the JWST to study the geometric and kinematic properties of a galaxy observed 500 Myr after the Big Bang.
1801.03555
Galactic Reddening in 3D from stellar photometry - An improved map
Green, Schlafly, Finkbeiner, Nix, et al
Present a new 3D map of interstellar dust reddening, covering 3 quarters of the sky (declinations greater than -30 deg) out to a distance of several kilo parsecs. The map is based on high-quality stellar photometry of 800 million stars from Pan-STARRS 1 and 2MASS. Divide the sky into sightlines containing a few hundred stars each, and then infer stellar distances and types, along with the line-of-sight dust distribution. The new map incorporates a more accurate average extinction law and an additional 1.5 years of Pan-STARRS 1 data, tracing dust to greater extinctions and at higher angular resolutions than the previous map. Out of the plane of the Galaxy, the map agrees well with 2D reddening maps derived from FIR dust emission. After accepting for a 15% difference in scale, find a mean scatter of 10% between the map and the Planck FIR emission-based dust map, out to a depth of 0.8 mag in E(r-z), with the level of agreement varying over the sky. The map can be downloaded at http://argonaut.skymaps.info, or by it sDOI: 10.7910/DVN/LCYHJG.
1801.03941
Full-sky ray-tracing simulation of weak lensing using ELUCID simulations: exploring galaxy intrinsic alignment and cosmic shear correlations
Wei, et al
The IA of galaxies is an important systematic effect in WL surveys, which can affect the derived cosmological parameters. One direct way to distinguish different alignment models and quantify their effects on the measurement is to produce mock WL surveys. In this work, use full-sky ray-tracing technique to produce mock images of galaxies from the ELUCID N-body sims run with the WMAP9 cosmology. The model assumes that the shape of central elliptical galaxy follows that of the DM halo, and spiral galaxy follows the halo spin. Using the mock galaxy images, a combination of galaxy intrinsic shape and the gravitational shear, compare the predicted tomographic shear correlation to the results of KiDS and DLS. It is found that the predictions stay between the KiDS and DLS results. Rule out a model in which the satellite galaxies are radially aligned with the center galaxy, otherwise the shear-correlations on small scales are too high. Most importantly, find that although the IA of spiral galaxies is very weak, they induce a positive correlation between the gravitational shear signal and the intrinsic galaxy orientation (GI). This is because the spiral galaxy is tangentially aligned with the nearby large-scale overdensity, contrary to the radial alignment of elliptical galaxy. The results explain the origin of detected positive GI term from the WL surveys. Conclude that in future analysis, the GI model must include the dependence on galaxy types in more detail. And the full-sky mock data introduced in this work can be available if you are interesting. :D
1801.xxxxx
The CosmicWatch desktop muon detector: a self-contained, pocket sized particle detector
Axani, Frankiewicz, Conrad
The CosmicWatch Desktop Muon Detector is a self-contained, hand-held cosmic ray muon detector that is valuable for astro/particle physics research applications and outreach. The material cost of each detector is under $100 and it takes a novice student approximately four hours to build their first detector. The detectors are powered via a USB connection and the data can either be recorded directly to a computer or to a microSD card. Arduino- and Python-based software is provided to operate the detector and an online application to plot the data in real-time. In this paper, describe the various design features, evaluate the performance, and illustrate the detectors capabilities by providing several example measurements.
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