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). ...

Aims. We present the detailed characterisation of a sample of 56 sources serendipitously detected in ALMA band 7 as part of the ALMA Large Program to INvestigate CII at Early Times (ALPINE). These sources, detected in COSMOS and ECDFS, have been used to derive the total infrared luminosity function (LF) and to estimate the cosmic star formation rate density (SFRD) up to z ≃ 6. Methods. We looked for counterparts of the ALMA sources in all the available multi-wavelength (from HST to VLA) and photometric redshift catalogues. We also made use of deeper UltraVISTA and Spitzer source lists and maps to identify optically dark sources with no matches in the public catalogues. We used the sources with estimated redshifts to derive the 250 μm rest-frame and total infrared (8–1000 μm) LFs from z ≃ 0.5 to 6. Results. Our ALMA blind survey (860 μm flux density range: ∼0.3–12.5 mJy) allows us to further push the study of the nature and evolution of dusty galaxies at high-z, identifying luminous and massive sources to redshifts and faint luminosities never probed before by any far-infrared surveys. The ALPINE data are the first ones to sample the faint end of the infrared LF, showing little evolution from z ≃ 2.5 to z ≃ 6, and a “flat” slope up to the highest redshifts (i.e. 4.5 <  z <  6). The SFRD obtained by integrating the luminosity function remains almost constant between z ≃ 2 and z ≃ 6, and significantly higher than the optical or ultra-violet derivations, showing a significant contribution of dusty galaxies and obscured star formation at high-z. About 14% of all the ALPINE serendipitous continuum sources are found to be optically and near-infrared (near-IR) dark (to a depth Ks ∼ 24.9 mag). Six show a counterpart only in the mid-IR and no HST or near-IR identification, while two are detected as [C II] emitters at z ≃ 5. The six HST+near-IR dark galaxies with mid-IR counterparts are found to contribute about 17% of the total SFRD at z ≃ 5 and to dominate the high-mass end of the stellar mass function at z >  3.

We analyze the gas kinematics of damped Lyα systems (DLAs) hosting high z gamma-ray bursts (GRBs) and those toward quasars (QSO-DLAs) focusing on three statistics: (1) ∆v 90 , the velocity interval encompassing 90% of the total optical depth, (2,3) W 1526 and W CIV , the rest equivalent widths of the Si II 1526 and C IV 1548 transitions. The ∆v 90 distributions of the GRB-DLAs and QSO-DLAs are similar, each has median ∆v 90 ≈ 80 km s −1 and a significant tail to several hundred km s −1. This suggests comparable galaxy masses for the parent populations of GRB-DLAs and QSO-DLAs and we infer the average dark matter halo mass of GRB galaxies is 10 12 M ⊙. The unique configuration of GRB-DLA sightlines and the presence (and absence) of fine-structure absorption together give special insight into the nature of high z, protogalactic velocity fields. The data support a scenario where the ∆v 90 statistic reflects dynamics in the interstellar medium (ISM) and W 1526 traces motions outside the ISM (e.g. halo gas, galactic-scale winds). The W 1526 statistic and gas metallicity [M/H] are tightly correlated, especially for the QSO-DLAs: [M/H] = a + b log(W 1526 /1Å) with a = −0.92 ± 0.05 and b = 1.41 ± 0.10. We argue that the W 1526 statistic primarily tracks dynamical motions in the halos of high z galaxies and interpret this correlation as a mass-metallicity relation with very similar slope to the trend observed in local, low-metallicity galaxies. Finally, the GRB-DLAs exhibit systematically larger W 1526 values (> 0.5Å) than the QSO-DLAs (< W 1526 >≈ 0.5Å) which may suggest galacticscale outflows contribute to the largest observed velocity fields.

We present a wide area (≈ 8×8 kpc), sensitive map of CO (2-1) emission around the nearby starburst galaxy M82. Molecular gas extends far beyond the stellar disk, including emission associated with the well-known outflow as far as 3 kpc from M82's midplane. Kinematic signatures of the outflow are visible in both the CO and Hi emission: both tracers show a minor axis velocity gradient and together they show double peaked profiles, consistent with a hot outflow bounded by a cone made of a mix of atomic and molecular gas. Combining our CO and Hi data with observations of the dust continuum, we study the changing properties of the cold outflow as it leaves the disk. While H 2 dominates the ISM near the disk, the dominant phase of the cool medium changes as it leaves the galaxy and becomes mostly atomic after about a kpc. Several arguments suggest that regardless of phase, the mass in the cold outflow does not make it far from the disk; the mass flux through surfaces above the disk appears to decline with a projected scale length of ≈ 1-2 kpc. The cool material must also end up distributed over a much wider angle than the hot outflow based on the nearly circular isophotes of dust and CO at low intensity and the declining rotation velocities as a function of height from the plane. The minor axis of M82 appears so striking at many wavelengths because the interface between the hot wind cavity and the cool gas produces Hα, hot dust, PAH emission, and scattered UV light. We also show the level at which a face-on version of M82 would be detectable as an outflow based on unresolved spectroscopy. Finally, we consider multiple constraints on the CO-to-H 2 conversion factor, which must change across the galaxy but appears to be only a factor of ≈ 2 lower than the Galactic value in the outflow. view relative to the OVRO map of Walter et al. (2002) but much coarser resolution. It has greatly improved resolution and sensitivity compared to the FCRAO singledish map by Taylor et al. (2001). It complements the CO J = 1 → 0 map of Salak et al. (2013), which has comparable resolution but much lower sensitivity than our HERA map, with ≈ 10× higher rms noise in T mb units for matched velocity channels. Similarly, it improves on the extent and sensitivity of the CO J = 3 → 2 map presented by Wilson et al. (2012). We will see below that comparing the CO J = 3 → 2, J = 2 → 1, and J = 1 → 0 lines yields interesting constraints on physical conditions.