1508.03336
Planet sensitivity from combined ground- and space-based microlensing observations
Zhu, Gould, et al
Present the first planet sensitivity analysis for microlensing events with simultaneous observations form space and ground. Present this analysis for 2 such events, which both show substantial planet sensitivity even though neither of them reached high magnification. Suggests an ensemble of low to moderate magnification events can also yield significant planet sensitivity and therefore probability to detect planets. The implications of the results to the ongoing and future space-based microlensing experiments to measure the Galactic distribution of planets are discussed.
1508.03375
Planck 2013 results. XXXI. Consistency of the Planck data
Planck Collaboration
The Planck design and scanning strategy provide many levels of redundancy that can be exploited to provide tests of internal consistency. One of the most important is the comparison of the 70 GHz and 100 GHz channels. Based on different instrument technologies, with feeds located differently in the focal plane, analyzed independently by different teams using different software, and near the minimum of diffuse foreground emission, these channels are in fact two different experiments. The 143 GHz channel has the lowest noise level on Planck, and is near the minimum of unresolved foreground emission. In this paper, analyse the level of consistency achieved in the 2013 Planck data. Concentrate on comparisons between the 70/100/143 GHz channel maps and power spectra, particularly over the angular scales of the first and second acoustic peaks, on maps masked for diffuse Galactic emission and for strong unresolved sources. Difference maps covering angular scales from 8 deg - 15 arcmin are consistent with noise, and show no evidence of CMB structure. Including small but important corrections for unresolved-source residuals, demonstrate agreement between 70 and 100 GHz power spectra averaged over 70<l<390 at the 0.8% level, and agreement between 143 and 100 GHz power spectra of 0.4% over the same ell range.
1508.03580
Impact of cosmological satellites on the vertical heating of the Milky Way disc
Moetazedian, Just
Present a high-res study of the impact of realistic satellite galaxies, extracted from cosmo sims of MW haloes including 6 Aquarius suites and Via Lactea II, on the dynamics of the galactic disc. The initial conditions for the multi-component NW galaxy were generated using the GalIC code, to ensure a system in real equilibrium state prior to addition of satellites. The candidate sub haloes that came closer than 25 kpc to the center of the host DM haloes, with initial mass M_tid>1e8=0.003 Mtid/Mdisc, were identified, inserted into the high res N-body sims and evolved for 2 Gyrs. Quantified the vertical heating due to such impacts by measuring the disc thickness, root-mean-square of z-coordinate, and vertical velocity dispersion sigma^2_z across the disc. According to the analysis the strength of the heating is strongly dependent on the high mass end of the sub halo distribution from the cosmo sims. The mean increase of the vertical dispersion is ~25 km^2/s^2/Gyr for R>4 kpc while, if the Aq-F-2 results are excluded, the mean heating is <12 km^2/s^2/Gyr. The observed vertical heating rate in the solar neighborhood has a value of 67 km^2/s^2/Gyr; taking into account the 1 sigma statistical dispersion around the mean, it lies just below the observed value of 144 km^2/s^2 after 2 Gyrs. Observed a general flaring of the disc height in the case of all 7 simulations in the outer disc where the thickness was increased by ~40% at 15 kpc. The 1 sigma cosmic variance corresponds to doubling the disc thickness in the outer region.
1508.03622
Eight ultra-faint galaxy candidates discovered in year two of the dark energy survey
The DES Collaboration
Report the discovery of eight new ultra-faint dwarf galaxy candidates in the second year of optical imaging data from the DES. Six of these candidates are detected at high confidence, while two additional lower-confidence candidates are identified in regions of incomplete or non-uniform survey coverage. The new stellar systems are found using three independent automated search techniques, and are identified as statistically significant over densities of individually resolved stars consistent with the isochrone and luminosity function of an old and metal-poor simple stellar population. the new systems are faint (Mv>-4.7 mag) and span a broad range of physical sizes (17 pc < r_1/2 < 181 pc) and heliocentric distances (25 kpc < D < 214 kpc). All of the new systems have central surface brightnesses (mu>27.5 mag arcsec^2) consistent with known ultra-faint dwarf galaxies. Roughly half of the DES candidates are more distant, less luminous, and/or have lower surface brightnesses than previously known MW satellite galaxies, and would have had a low probability of detection if observed by SDSS. A large fraction of satellite candidates are found in the southern half of the DES footprint in proximity to the Magellanic Clouds. Find that the DES data alone exclude (p<0.001) a spatially isotropic distribution of MW satellites, and that this distribution can be well, although not uniquely, explained by a model in which several of the observed DES satellites are associated with the Magellanic system. Including the current sample, the model predicts that ~100 ultra-faint galaxies with physical properties comparable to the DES satellites might exist over the full sky and that 20-30% of these would be spatially associated wit the Magellanic Clouds.
No comments:
Post a Comment