No abstract

The origin and growth of magnetic fields in galaxies is still something of an enigma. It is generally assumed that seed fields are amplified over time through the dynamo effect, but there are few constraints on the timescale. It was recently demonstrated that field strengths as traced by rotation measures of distant (and hence ancient) quasars are comparable to those seen today, but it was unclear whether the high fields were in the unusual environments of the quasars themselves or distributed along the lines of sight. Here we report high-resolution spectra that demonstrate that the quasars with strong Mg II absorption lines are unambiguously associated with larger rotation measures. Because Mg ii absorption occurs in the haloes of normal galaxies along the sightlines to the quasars, this association requires that organized fields of surprisingly high strengths are associated with normal galaxies when the Universe was only about one-third of its present age.

We study the chemical abundances of the interstellar medium surrounding high-z gamma-ray bursts (GRBs) through analysis of the damped Ly systems ( DLAs) identified in afterglow spectra. These GRB DLAs are characterized by large H i column densities N H i and metallicities [M/H] spanning 1/100 to nearly solar, with median ½M/H > À1 dex. The majority of GRB DLAs have [M/H] values exceeding the cosmic mean metallicity of atomic gas at z > 2; i.e., if anything, the GRB DLAs are biased to larger metallicity. We also observe (1) large [Zn/Fe] values (> +0.6 dex) and subsolar Ti/Fe ratios, which imply substantial differential depletion; (2) large /Fe ratios, suggesting nucleosynthetic enrichment by massive stars; and (3) low C 0 /C + ratios (<10 À4 ). Quantitatively, the observed depletion levels and C 0 /C + ratios of the gas are not characteristic of cold, dense H i clouds in the Galactic interstellar medium (ISM). We argue that the GRB DLA represents the ISM near the GRB but not gas directly local to the GRB (e.g., its molecular cloud or circumstellar material). We compare these observations with DLAs intervening in background quasars (QSO DLAs). The GRB DLAs exhibit larger N H i values, higher /Fe and Zn/Fe ratios, and higher metallicity than the QSO DLAs. Although these differences are statistically significant, the offsets are relatively modest (N H i excepted). We argue that the differences result primarily from galactocentric radius-dependent differences in the ISM: GRB DLAs preferentially probe denser, more depleted, higher metallicity gas located in the inner few kiloparsecs, whereas QSO DLAs are more likely to intersect the less dense, less enriched, outer regions of the galaxy. Finally, we investigate whether dust obscuration may exclude GRB DLA sight lines from QSO DLA samples; we find that the majority of GRB DLAs would be recovered, which implies little observational bias against large N H i systems.

We present the ancillary data and basic physical measurements for the galaxies in the ALMA Large Program to Investigate C + at Early Times (ALPINE) survey − the first large multi-wavelength survey which aims at characterizing the gas and dust properties of 118 main-sequence galaxies at redshifts 2 Faisst et al. 4.4 < z < 5.9 via the measurement of [C II] emission at 158 µm and the surrounding far-infrared (FIR) continuum in conjunction with a wealth of optical and near-infrared data. We outline in detail the spectroscopic data and selection of the galaxies as well as the ground-and space-based imaging products. In addition, we provide several basic measurements including stellar masses, star formation rates (SFR), rest-frame ultra-violet (UV) luminosities, UV continuum slopes (β), and absorption line redshifts, as well as Hα emission derived from Spitzer colors. Overall, we find that the ALPINE sample is representative of the 4 < z < 6 galaxy population and only slightly biased towards bluer colors (∆β ∼ 0.2). Using [C II] as tracer of the systemic redshift (confirmed for one galaxy at z = 4.5 for which we obtained optical [O II]λ3727 µm emission), we confirm red shifted Lyα emission and blue shifted absorption lines similar to findings at lower redshifts. By stacking the rest-frame UV spectra in the [C II] rest-frame we find that the absorption lines in galaxies with high specific SFR are more blue shifted, which could be indicative of stronger winds and outflows.

Galaxies are thought to be fed by the continuous accretion of intergalactic gas, but direct observational evidence has been elusive. The accreted gas is expected to orbit about the galaxy's halo, delivering not just fuel for starformation but also angular momentum to the galaxy, leading to distinct kinematic signatures. We report observations showing these distinct signatures near a typical distant star-forming galaxy where the gas is detected using a background quasar passing 26 kpc from the host. Our observations indicate that gas accretion plays a major role in galaxy growth since the estimated accretion rate is comparable to the star-formation rate.At all epochs, galaxies have short gas depletion time scales (1,2); to sustain the observed levels of star-formation over many billions of years, galaxies must continuously replenish their gas 1 arXiv:1306.0134v2 [astro-ph.CO] 3 Jul 2013 reservoir with fresh gas accreted from the vast amounts available in the intergalactic medium.In numerical cosmological simulations (3-5), the accretion phenomenon is often referred to as 'cold accretion' (6) and this term describes the mass regime where the accretion is most efficient (7,8). The cold accreted gas should orbit about the halo before falling in to build the central disk, delivering fuel for star formation and also angular momentum to shape the outer parts of the galaxy (9, 10). Thus, accreting material should co-rotate with the central disk in the form of a warped, extended cold gaseous disk, producing distinct kinematic signatures in absorption systems. In particular, the gas kinematics are expected to be offset by about 100 km s −1 from the galaxy's systemic velocity and these kinematic signatures of gas accretion should be observable in suitable quasar absorption line systems (6, 11-13).Here, we describe observations of a background quasar whose apparent location on the sky is fortuitously aligned with the galaxys projected major-axis, making it possible to test these predictions The associated star-forming galaxy with redshift z = 2.3285 is located just 26 kpc from the damped Lyman absorber (DLA) seen towards the quasar HE 2243−60 (14). The galaxy was detected in our z 2 SINFONI (15) survey called the SINFONI Mg II Program for Line Emitters (SIMPLE) (16). Recent adaptive optics (AO) assisted SINFONI observations (17) of this z = 2.3285 star-forming galaxy (Fig. 1a) obtained at the Very Large Telescope (VLT) with ∼ 1 kpc (0.25 arc sec) resolution (table S1) allow us to map the emission kinematics with precision ( Fig. 1b and figs S3 and S4). The kinematics reveal that this galaxy has physical properties (Table 1) (17) shows that the gas metallicity can give us insights into the physical nature of the gas. In particular, the total H I column is log(N H /cm −2 ) 20.6 (i.e. almost entirely neutral) and, from the undepleted low-ionisation ion Zn II, the gas metallicity ([Zn/H] = −0.72 ± 0.05) is much lower than that of the galaxy. This comparison disfavor an outflow scenario because these tend to be metal rich (19). ...