We present the Ðrst results of a spectroscopic survey of Lyman break galaxies (LBGs) in the nearinfrared aimed at detecting the emission lines of [O II], [O III], and Hb from the H II regions of normal star-forming galaxies at z^3. From observations of 15 objects with the Keck telescope and the Very Large Telescope augmented with data from the literature for an additional four objects, we reach the following main conclusions. The rest-frame optical properties of LBGs at the bright end of the luminosity function are remarkably uniform, their spectra are dominated by emission lines, [O III] is always stronger than Hb and [O II], and projected velocity dispersions are between 50 and 115 km s~1. Contrary to expectations, the star formation rates deduced from the Hb luminosity are on average no larger than those implied by the stellar continuum at 1500 presumably any di †erential extinction between A ; rest-frame optical and UV wavelengths is small compared to the relative uncertainties in the calibrations of these two star formation tracers. For the galaxies in our sample, the abundance of oxygen can only be determined to within 1 order of magnitude without recourse to other emission lines ([N II] and Ha), which are generally not available. Even so, it seems well established that LBGs are the most metalenriched structures at z^3, apart from quasi-stellar objects, with abundances greater than about 1/10 solar and generally higher than those of damped Lya systems at the same epoch. They are also signiÐ-cantly overluminous for their metallicities ; this is probably an indication that their mass-to-light ratios are low compared to present-day galaxies. At face value, the measured velocity dispersions imply virial masses of about 1010 within half-light radii of 2.5 kpc. The corresponding mass-to-light ratios, M _ M/L B 0.15 in solar units, are indicative of stellar populations with ages between 108 and 109 yr, consistent with the UV-optical spectral energy distributions. However, we are unable to establish conclusively whether or not the widths of the emission lines reÑect the motions of the H II regions within the gravitational potential of the galaxies, even though in two cases we see hints of rotation curves. All 19 LBGs observed show evidence for galactic-scale superwinds ; such outÑows have important consequences for regulating star formation, distributing metals over large volumes, and allowing Lyman continuum photons to escape and ionize the intergalactic medium.

We present near-infrared spectroscopy of Hα emission lines in a sample of 16 star-forming galaxies at redshifts 2.0 < z < 2.6. Our targets are drawn from a large sample of galaxies photometrically selected and spectroscopically confirmed to lie in this redshift range. We have obtained this large sample with an extension of the broadband U n GR color criteria used to identify Lyman break galaxies at z ∼ 3. The primary selection criterion for IR spectroscopic observation was proximity to a QSO sight-line; we therefore expect the galaxies presented here to be representative of the sample as a whole. Six of the galaxies exhibit spatially extended, tilted Hα emission lines; rotation curves for these objects reach mean velocities of ∼ 150 km s −1 at radii of ∼ 6 kpc, without corrections for inclination or any other observational effect. The velocities and radii give a mean dynamical mass of M ≥ 4 × 10 10 M ⊙ . We have obtained archival HST images for two of these galaxies; they are morphologically irregular. One-dimensional velocity dispersions for the 16 galaxies range from ∼ 50 to ∼ 260 km s −1 , and in cases where we have both virial masses implied by the velocity dispersions and dynamical masses derived from the spatially extended emission lines, they are in rough agreement. We compare our kinematic results to similar measurements made at z ∼ 3, and find that both the observed rotational velocities and velocity dispersions tend to be larger at z ∼ 2 than at z ∼ 3. We also calculate star formation rates (SFRs) from the Hα luminosities, and compare them with SFRs calculated from the UV continuum luminosity. We find a mean SFR Hα of 16 M ⊙ yr −1 and an average SFR Hα /SFR UV ratio of 2.4, without correcting for extinction. We see moderate evidence for an inverse correlation between the UV continuum luminosity and the ratio SFR Hα /SFR UV , such as might be observed if the UV-faint galaxies suffered greater extinction. We discuss the effects of dust and star formation history on the SFRs, and conclude that extinction is the most likely explanation for the discrepancy between the two SFRs.

Galaxies had their most significant impact on the Universe when they assembled their first generations of stars. Energetic photons emitted by young, massive stars in primeval galaxies ionized the intergalactic medium surrounding their host

We describe ISAAC/ESO‐VLT observations of the Hαλ6563 Balmer line of 33 field galaxies from the Canada–France Redshift Survey (CFRS) with redshifts selected between 0.5 and 1.1. We detect Hα in emission in 30 galaxies and compare the properties of this sample with the low‐redshift sample of CFRS galaxies at z∼ 0.2. We find that the Hα luminosity, L(Hα), is tightly correlated to M(BAB) in the same way for both the low‐ and high‐redshift samples. L(Hα) is also correlated to L([O ii]λ3727), and again the relation appears to be similar at low and high redshifts. The ratio L(lsqb;O ii])/L(Hα) decreases for brighter galaxies by as much as a factor of 2 on average. Derived from the Hα luminosity function, the comoving Hα luminosity density increases by a factor 12 from 〈z〉= 0.2 to 〈z〉= 1.3. Our results confirm a strong rise of the star formation rate (SFR) at z < 1.3, proportional to (1 +z)4.1±0.3 (with H0= 50 km s−1 Mpc−1, q0= 0.5). We find an average SFR(2800 Å)/SFR (Hα) ratio of 3.2 using the Kennicutt SFR transformations. This corresponds to the dust correction that is required to make the near‐ultraviolet data consistent with the reddening‐corrected Hα data within the self‐contained, I‐selected CFRS sample.

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THESEUS is a space mission concept aimed at exploiting Gamma-Ray Bursts for investigating the early Universe and at providing a substantial advancement of multi-messenger and time-domain astrophysics. These goals will be achieved through a unique combination of instruments allowing GRB and X-ray transient detection over a broad field of view (more than 1sr) with 0.5-1 arcmin localization, an energy band extending from several MeV down to 0.3 keV and high sensitivity to transient sources in the soft X-ray domain, as well as on-board prompt (few minutes) followup with a 0.7 m class IR telescope with both imaging and spectroscopic capabilities. THESEUS will be perfectly suited for addressing the main open issues in cosmology such as, e.g., star formation rate and metallicity evolution of the inter-stellar and intra-galactic medium up to redshift ∼10, signatures of Pop III stars, sources and physics of reionization, and the faint end of the galaxy luminosity function. In addition, it will provide unprecedented capability to monitor the X-ray variable sky, thus detecting, localizing, and identifying the electromagnetic counterparts to sources of gravitational radiation, which may be routinely detected in the late '20s / early '30s by next generation facilities like aLIGO/ aVirgo, eLISA, KAGRA, and Einstein Telescope. THESEUS will also provide powerful synergies with the next generation of multi-wavelength observatories (e.g., LSST, ELT, SKA, CTA, ATHENA).

Abstract. We report on the results of medium-resolution spectroscopy of GRS 1915+105 in the near-infrared H and K band using the 8 m VLT at ESO. We clearly identify absorption bandheads from 12 CO and 13 CO. Together with other features this results in a classification of the mass-donating star in this binary as a K-M III star, clearly indicating that GRS 1915+105 belongs to the class of low-mass X-ray binaries (LMXB).

Aims. The Lyα luminosity function (LF) of high-redshift Lyα emitters (LAEs) is one of the few observables of the re-ionization epoch accessible with 8-10 m class telescopes. The evolution of the LAE LF with redshift is dependent upon the physical evolution of LAEs and the ionisation state of the Universe towards the end of the Dark Ages. Methods. We performed a narrow-band imaging program at 1.06 μm using CFHT/WIRCam. The observations target Lyα emitters at redshift z ∼ 7.7 in the CFHT-LS D1 field. From these observations we derived a photometric sample of 7 LAE candidates at z ∼ 7.7. Results. We derive luminosity functions for the full sample of seven objects and for subsamples of four objects. Assuming the brightest objects in our sample are real, we find that the resulting luminosity function is not consistent with previous work at lower redshifts. More definitive conclusions will require spectroscopic confirmation.