Day 985

Friday.


1510.02097
Mass measurements of isolated objects from spaced-based microlensing
Zhu, ... Gould, et al

Report on the mass and distance measurements of 2 single-lens events from 2015 Spitzer microlensing campaign.  With both finite-source effect and microlens parallax measurements, find that the lens of OGLE-2015-BLG1268 is a 47±7 M_J brown dwarf at 5.4±1.0 kpc, and that the lens of -0763 is a 0.50±0.04 Msun star at 6.9±1.0 kpc.  Show that the probability to definitively measure the mass of isolated micro lenses, including isolated stellar mass BHs and free floating planets, is dramatically increased once simultaneous ground- and space-based observations are conducted.


1510.02101
Detectability of local  group dwarf galaxy analogues at high redshifts
Patej, Loeb

The dwarf galaxies of the Local Group are believed to be similar to the most abundant galaxies during the epoch of reionization (z>6).  As a result of their proximity, there is a wealth of information that can be obtained about these galaxies; however, due to their low surface brightnesses, detecting their progenitors at high redshifts is challenging.  Compare the physical properties of these dwarf galaxies to those of galaxies detected at high redshifts using HST and Spitzer observations and consider the promise of the upcoming JWST on the prospects for detecting high redshift analogues of these galaxies.


1510.02106
The 3D-HST survey: Hubble Space Telescope WFC3/G141 grism spectra, redshifts, and emission line measurements from $/sim 100,000$ galaxies
Momcheva, Bramer, van Dokkum, ... et al

Present reduced data and data products from the 3D-HST survey, a 248-orbit HST Treasury program.  The survey obtained WFC3 G141 grism spectrosocopy in four of the five CANDELS fields: AEGIS, COSMOS, GOODS-S, and UDS, along with WFC3 H_140 imaging, parallel ACS G800L spectroscopy, and parallel I_814 imaging.  A previous paper (Skelton+ 2014) presented photometric catalogs in these 4 fields and in GOODS-N, the fifth CANDELS field.  Describe and present the WFC3 G141 spectroscopic data, again augmented with data from GO-1600 in GOODS-N.  The data analysis is complicated by the fact that no slits are used: all objects in the WFC3 field are dispersed, and many spectra overlap.  Developed software to automatically and optimally extract interlaced 2d and 1d spectra for all objects in the Skelton+2014 photometric catalogs.  The 2d spectra and the multi-band photometry were fit simultaneously to determine redshifts and emission line strengths, making the morphology of the galaxies explicitly into account.  The resulting catalog has 98,663 measured redshifts and line strengths down to JH_IR<26 and 22,548 with JH_IR<24, where continuum emission is comfortably detected.  Of this sample 5,459 galaxies are at z>1.5 and 9.621 are at 0.7<z<1.5, where Ha falls in the G141 wavelength coverage.  Based on comparisons with ground-based spec-z's, and on analyses of paired galaxies and repeat observations, the typical redshift error for JH_IR<24 galaxies in the catalog is sigma_z~0.003(1+z), i.e., one native WFPC3 pixel.  The 3sigma limit for emission line fluxes of point sources is 1.5e-17 erg/s/cm2.  Show various representations of the full dataset, as well as individual examples that highlight the range of spectra that is found in the survey.


1510.02296
Detailed modeling of the 21-cm forest
Semelin

The 21-cm forest is a promising probe of the Epoch of Reionization.  The local state of the IGM is encoded in the spectrum of a background source (radio-loud quasars or gamma ray burst afterglow) by absorption at the local 21-cm wavelength, resulting in a continuous and fluctuating absorption level.  Small-scale structures (filaments and minihaloes)  in the IGM are responsible for the strongest absorption features.  The absorption can also be modulated on large scales by inhomogeneous heating and Wouthuysen-Field coupling.  Present the results from a simulation that attempts to preserve the cosmological environment while resolving some of the small-scale structures (a few kpc resolution in a 50 Mpc/h box).  The simulation couples the dynamics and the ionizing radiative transfer and includes X-ray and Lyman lines radiative transfer for a detailed physical modeling.  As a result, find that soft X-ray self-sheidling, Lyman-alpha self-sheilding and shock heating all have an impact on the predicted values of the 21-cm optical depth of moderately overdense structures like filaments.  A correct treatment of the peculiar velocities is also critical.  Modeling these processes seems necessary for accurate predictions and can be done only at high enough resolution.  As a result, based on the fiducial model, estimate that LOFAR should be abe to detect a few (strong) absorption features in a frequency range of a few tens of MHz for a 20 mJy source located at z=10, while the SKA would extract a large fraction of the absorption information for the same source.