BOSS DR12 survey: Clustering of galaxies and Dark Matter Haloes
Sergio Rodriguez, UAM, Madrid and Cal. Berkeley
BOSS SDSS-III is the largest redshift survey for the large scale structure and a powerful sample for the study of the low redshift Baryonic Acoustic Oscillations. We combine the features of the survey, such as, geometry, angular incompleteness and stellar mass incompleteness, with the BigMultiDark cosmological simulation to do a study of the distribution of galaxies in the dark matter halos. Using this large N-Body simulation and the halo abundance matching technique, we found a remarkably good agreement with the 2-point and 3-point statistics of the data.
Evolving Perspectives on the Atmosphere and Climate of Mars
Dr. Richard Zurek, JPL
Abstract: The planet Mars has both fascinated and tantalized humankind since the invention of the telescope and now well into the age of exploration from space. The first of three waves of space missions to Mars were flyby spacecraft that returned images of a heavily cratered planet with a thin atmosphere, suggesting Mars was more like the Moon than an older Earth. However, Mariner 9, the first spacecraft to orbit another planet, found vast channel and valley networks carved into its surface, as well as towering volcanoes, suggesting that ancient Mars was once much more Earth-like. Subsequent missions have landed on the planet and new orbiters have probed the planet at ever increasing spatial resolution and spectral coverage. As a result of the latest round of space exploration, Mars is revealed to be a complex, diverse planet— one whose climate has changed dramatically over time from an ancient atmosphere where water was active on its surface to a drier, thinner atmosphere shaped by periodic ice ages, to the present atmosphere where dynamic change continues today.
Dr. Zurek is the Chief Scientist in the Mars Program Office, Project Scientist, MRO.
Exploring Impact Heating of the Early Martian Climate
Kathryn Steakley, NMSU
ABSTRACT: Geological evidence implies that Mars may have had a more warm and wet environment during the late Noachian / early Hesperian era (3.5–3.8 billion years ago), but climate models struggle to reproduce such warm conditions. Prior studies with one-dimensional atmospheric models indicate that the water and energy from impacts could provide enough greenhouse warming to raise temperatures above the freezing point of liquid water for many years. We will use the NASA Ames Research Center Mars GCM to characterize potential atmospheric changes induced by impactors ranging in diameter from 50 m to 100 km on a range of early Mars surface pressure scenarios (10-mbar, 100-mbar, 300-mbar, 1-bar, 2-bar, 3-bar). Our objectives are 1) to examine the temperature behavior of the early Martian climate following impacts and determine if environmental conditions on its surface could support liquid water for extended periods of time, and 2) to quantify precipitation rates and examine rainfall patterns on a simulated early Martian surface following impacts and determine if this mechanism is possibly responsible for the formation of observed river valley networks on Mars. Examining climate conditions after impacts with a GCM will allow us to test a potential mechanism for heating the early Martian atmosphere, constrain the magnitude and temporal duration of these potential heating events, and provide insight regarding the availability of liquid water on early Mars which is relevant to its past habitability.
Galaxy Evolution during the Epoch of Reionization
Steve Finkelstein, University of Texas at Austin
Abstract: The advent of the Wide Field Camera 3 on the Hubble Space Telescope has heralded a new era in our ability to study the earliest phases of galaxy formation and evolution. The number of candidates for galaxies now known at redshifts greater than six has grown to be in the thousands. This allows us to move beyond mere counting of galaxies, to endeavor to understand the detailed physics regulating the growth of galaxies. I will review the recent progress our group in Texas has made in this arena using the exquisite datasets from the CANDELS and Frontier Fields programs. Specifically, our detailed new measurements of both the evolution of the stellar mass function and rest-frame UV luminosity function now allow us to probe the effect of feedback on low-mass galaxies, the star-formation efficiency in high-mass galaxies, and the contribution of galaxies to the reionization of the universe. Our most recent result comes from the Frontier Fields, where we have used an advanced technique to remove the light from the cluster galaxies to uncover z > 6 galaxies as faint as M_UV=-13. Our updated luminosity functions show no sign of a turnover down to these extremely faint levels, providing the first empirical test of reionization models which require such faint galaxies, and is in modest tension with simulations which predict a turnover at brighter levels. I will also discuss our spectroscopic followup efforts, which have yielded two of the four highest redshift confirmed galaxies, and also provide further insight into reionization, by the scattering of Lyman alpha emission by neutral gas in the intergalactic medium. I will conclude with a look ahead to the problems we can expect to tackle with ALMA, JWST, and even more future facilities.
High Resolution Spectroscopy with Immersion Grating Infrared Spectrometer (IGRINS)
Hwihyun Kim, KASI/UT Austin
The Immersion Grating Infrared Spectrometer (IGRINS) is a revolutionary instrument that exploits broad spectral coverage at high-resolution (R=45,000) in the near-infrared. IGRINS employs a silicon immersion grating as the primary disperser of the white pupil, and volume-phase holographic gratings cross-disperse the H and K bands onto Teledyne Hawaii-2RG arrays. IGRINS provides simultaneous wavelength coverage from 1.45 – 2.45 microns in a compact cryostat. I will summarize the performance and various science programs of IGRINS since commissioning in Summer 2014. With IGRINS we have observed such as Solar System objects, nearby young stars, star-forming regions like Taurus and Ophiuchus, the Galactic Center, and planetary nebulae.
The second half of my talk will be focused on the study of ionized and neutral gas in an ultracompact HII region Monoceros R2. We obtained the IGRINS spectra of Mon R2 to study the kinematic patterns in the areas where ionized and molecular gases interact. The position-velocity maps from the IGRINS spectra demonstrate that the ionized gases (Brackett and Pfund series, He and Fe emission lines;Δv ≈ 40km/s) flow along the walls of the surrounding clouds. This is consistent with the model by Zhu et al. (2005, 2008). In the PV maps of the H2 emission lines there is no obvious motion (Δv < ~10km/s) of the molecular hydrogen right at the ionization boundary. This implies that the molecular gas is not taking part in the flow as the ionized gas is moving along the cavity walls.
Dr. Janna Levin