Search

We present a suite of semianalytic disk-bulge-halo models for the Andromeda galaxy (M31) that satisfy three fundamental conditions: (1) internal self-consistency, (2) consistency with observational data, and (3) stability of the disk against the formation of a central bar. The models are chosen from a set first constructed by Kuijken & Dubinski. We develop an algorithm to search the parameter space for this set in order to best match observations of the M31 rotation curve, inner velocity dispersion profile, and surface brightness profile. Models are obtained for a large range of bulge and disk masses; we find that the disk mass must be [?]8 x 1010 M and that the preferred value for the bulge mass is 2.5 x 1010 M. N-body simulations are carried out to test the stability of our models against the formation of a bar within the disk. We also calculate the baryon fraction and halo concentration parameter for a subset of our models and show that the results are consistent with the predictions from cosmological theories of structure formation. In addition, we describe how gravitational microlensing surveys and dynamical studies of globular clusters and satellites can further constrain the models.

We present an overview of a deep transient survey of the COSMOS field with the Subaru Hyper Suprime-Cam (HSC). The survey was performed for the 1.77 deg2ultra-deep layer and 5.78 deg2deep layer in the Subaru Strategic Program over six- and four-month periods from 2016 to 2017, respectively. The ultra-deep layer reaches a median depth per epoch of 26.4, 26.3, 26.0, 25.6, and 24.6 mag in g, r, i, z, and ybands, respectively; the deep layer is ∼0.6 mag shallower. In total, 1824 supernova candidates were identified. Based on light-curve fitting and derived light-curve shape parameter, we classified 433 objects as Type Ia supernovae (SNe); among these candidates, 129 objects have spectroscopic or COSMOS2015 photometric redshifts and 58 objects are located at z> 1. Our unique data set doubles the number of Type Ia SNe at z> 1 and enables various time-domain analyses of Type II SNe, high-redshift superluminous SNe, variable stars, and active galactic nuclei.

We report the results of our search for the 380 GHz H2O line emissions from the quadruply lensed quasi-stellar object (QSO) MG J0104+0534 at z= 2.639 with the Atacama Large Millimeter/submillimeter Array. Our observation shows a tentative detection of the 380 GHz line from the lensed QSO, and the line spectrum shows a broad spectral distribution that has a velocity width of ∼290 km s−1and a peak flux of ∼0.8 mJy. The integrated intensity map of the H2O line shows lensed emissions at the A1 and A2 component of the QSO, with the A2 component slightly resolved. The integrated line flux ratio between the A1 and A2 components shows an unexpected difference from the continuum flux ratio. Based on our gravitational lens modeling, assuming our tentative detection is real, this flux ratio anomaly would suggest that the 380 GHz line emissions come from two or three spatially displaced locations in the QSO, with the dominant one located at the position of the continuum emission from the QSO, and the other one(s) displaced from the continuum by ∼1.5 kpc on the source plane.

The Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) is an excellent survey for the search for strong lenses, thanks to its area, image quality, and depth. We use three different methods to look for lenses among 43000 luminous red galaxies from the Baryon Oscillation Spectroscopic Survey (BOSS) sample with photometry from the S16A internal data release of the HSC-SSP. The first method is a newly developed algorithm, named YattaLens, which looks for arc-like features around massive galaxies and then estimates the likelihood of an object being a lens by performing a lens model fit. The second method, Chitah, is a modeling-based algorithm originally developed to look for lensed quasars. The third method makes use of spectroscopic data to look for emission lines from objects at a different redshift from that of the main galaxy. We find 15 definite lenses, 36 highly probable lenses, and 282 possible lenses. Among the three methods, YattaLens, which was developed specifically for this study, performs best in terms of both completeness and purity. Nevertheless, five highly probable lenses were missed by YattaLensbut found by the other two methods, indicating that the three methods are highly complementary. Based on these numbers, we expect to find ∼300 definite or probable lenses by the end of the HSC-SSP.

Hyper Suprime-Cam (HSC) is a wide-field imaging camera on the prime focus of the 8.2-m Subaru telescope on the summit of Mauna Kea in Hawaii. A team of scientists from Japan, Taiwan, and Princeton University is using HSC to carry out a 300-night multi-band imaging survey of the high-latitude sky. The survey includes three layers: the Wide layer will cover 1400 deg2in five broad bands (grizy), with a 5 σ point-source depth of r≈ 26. The Deep layer covers a total of 26 deg2in four fields, going roughly a magnitude fainter, while the UltraDeep layer goes almost a magnitude fainter still in two pointings of HSC (a total of 3.5 deg2). Here we describe the instrument, the science goals of the survey, and the survey strategy and data processing. This paper serves as an introduction to a special issue of the Publications of the Astronomical Society of Japan, which includes a large number of technical and scientific papers describing results from the early phases of this survey.