Inter[Stellar and Galactic] Medium Program of Studies (IMPS)

Galaxies hosting z~2 quasars are the high-z progenitors of today’s massive red and dead galaxies. With close pairs of quasars at different redshifts, a background quasar can be used to study a foreground quasar’s halo gas in absorption, providing information about feedback, quenching, and the physics of massive galaxy formation. We have obtained echellete spectra of bright background quasars in projected pairs with small angular separations corresponding to < 300 kpc at the redshift of the foreground quasars. Most of the systems reveal optically thick gas (N_HI >= 10^17 cm^-2) coincident with foreground quasar redshift. We have detected extreme kinematics with metal absorption lines extending to ~ +1000 km s^-1 relative to z_fg. We have also found gas with nearly solar metallicity. Furthermore, there is evidence of anisotropic or intermittent illumination on the gas by the the foreground quasars.

The primordial chemistry of the Universe consisted almost entirely of the lightest elements of the periodic table, including hydrogen, helium, lithium, and their isotopes. These primordial nuclides were made just minutes after the Big Bang, during a period known as Big Bang Nucleosynthesis. The relative abundances of these elements offer an intimate view of the physical laws that were in operation moments after the Big Bang, and currently provide the most reliable probe of the very early Universe. To measure the primordial elements, environments must be found that remain as uncontaminated as possible since the Big Bang. The IMPS group studies this primordial chemistry by identifying neutral clouds of gas that are located, by chance, along the line-of-sight to a more distant quasar. In particular, this technique can measure the ratio of deuterium to hydrogen atoms (D/H); detailed numerical calculations have shown that (D/H) is very sensitive to the total amount of visible matter in the present day Universe.

The HALO7D survey provides an unprecedented opportunity to make major advances in the study of galactic wind scaling relations by providing spectra with adequate signal-to-noise (S/N) for a large sample of individual galaxies in CANDELS fields at z~1, as opposed to stacked spectra of hundreds of galaxies (Weiner et al. 2009; Rubin et al. 2010; Bordoloi et al. 13). As a demonstration of the quality of the distant galaxy spectra from the HALO7D survey, panels a & b show unsmoothed example spectra of V=22.5 magnitude galaxy at redshift z=1.35. This galaxy has been observed both in HALO7D (6 hrs) and DEEP3 (1 hr) surveys. As expected, the S/N of the HALO7D spectrum is about 2.5 times higher than that of DEEP3 spectrum, and the low-ionization UV absorption and emission lines of both Mg II and Fe II are clearly observed. Sine the Mg II absorption lines are contaminated with emission, a more reliable but weaker Fe II absorption lines, provide calibrating references and independent checks for the Mg II velocity profiles (e.g., Prochaska et al. 2011). These lines however are vaguely conspicious in the unsmoothed DEEP3 spectra. Furthermore, the detectability of strong Mg II and Fe II emission lines in the example HALO7D spectrum also demonstrates the potential of our survey to study the spatial exent of the wind thereby constrain the much sought-after mass-loading factor, a critical ingredient for all wind models. Note however that when the DEEP3 spectrum is smoothed by 6 pixel (Panel c), enough S/N is achieved to measure the UV absorption lines. Thus indicating that V ~ 23.5 is reachable with 8 hour exposures and some smoothing to study individual galaxies in the HALO7D survey.

This figure shows a snapshot of the early collapse of a 10^6 M_\odot turbulent cloud in the process of forming stars. The column density is shown by the color gradients and velocity distribution is shown by the arrows. The stars will form in the densest regions and the radiation emitted by these stars will heat up the surrounding gas. This effect of stellar feedback can potentially inhibit subsequent star formation and may also cause mass to be ejected from the natal cloud.

White dwarf imaging and spectroscopy in star clusters reveals the total integrated mass loss that stars suffer through post-main sequence evolution. The initial-to-final mass relation therefore represents a powerful input to chemical evolution models of galaxies (including enrichment of the interstellar medium) and therefore enhances our understanding of star formation efficiencies in these systems.