K. Ohta, K. Yabe, I. Iwata, M. Sawicki, M. Akiyama, N. Tamura, K. Aoki
Properties of Lyman Break Galaxies at $z\sim5$ are presented and are compared with those at $z\sim 2-3$ LBGs to see evolution of LBGs from $z\sim5$ to $z \sim3-2$. The LBGs at $z\sim5$ are tend to have smaller stellar masses, but they may show large star formation rates and specific star formation rates.
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We review the Lyan alpha emission in local star-forming galaxies. In most cases as already shown by the IUE, the emission is absent or much weaker than expected. This occurs because Lyman alpha photons can be resonantly scattered by the neutral gas and destroyed by even very low amounts of dust. However new Hubble Space Telescope observations (HST) indicate that other factors such as the velocity structure of the gas play a crucial role. Gas flows are likely to occur as powered by the kinetic energy released via stellar winds and supernova. We propose a scenario based on the hydrodynamics of s…
I discuss the properties of gas-rich forming galaxies. I particularly emphasize the latest results on Lyman alpha emission that are relevant to the search of distant young galaxies. The interdependance of the Lyman alpha escape with the properties of the ISM in starburst galaxies is outlined. A new model from G. Tenorio-Tagle and his collaborators explaining Lyman alpha profiles in starburst galaxies from the hydrodynamics of superbubbles powered by massive stars is presented. I stress again that since Lyman alpha is primarely a diagnostic of the ISM, it is mandatory to understand how the ISM …
We investigate the chemical abundances of local star-forming galaxies which cause Damped Lyman Alpha lines. A metallicity versus redshift diagram is constructed, on which the chemical abundances of low-redshift star-forming galaxy populations are compared with those of high-redshift Damped Lyman Alpha systems. We disucss two types of experiments on individual star-forming galaxies. In the first, the Damped Lyman Alpha line is created against an internal ultraviolet light source generated by a star-forming cluster or a supernova explosion. In the second, the Damped Lyman Alpha line is seen agai…
Can the submillimeter counts and background be produced by applying a locally derived extinction correction to the population of Lyman break galaxies? We investigate the submillimeter emission of two strongly lensed Lyman break galaxies (MS1512+36-cB58 and MS1358+62-G1) and find that the procedure that is used to predict the submillimeter emission of the Lyman break galaxy population overpredicts the observed 850micron fluxes by up to a factor of 14. This result calls for caution in applying local correlations to distant galaxies. It also shows that large extinction corrections on Lyman break …
Can the submillimetre counts and background be produced by applying a locally derived extinction correction to the population of Lyman break galaxies? We investigate the submillimetre emission of two strongly lensed Lyman break galaxies (MS1512+36-cB58 and MS1358+62-G1) and find that the procedure that is used to predict the submillimetre emission of the Lyman break galaxy population overpredicts the observed 850 micron fluxes by a factor of up to 14. This result calls for caution in applying local correlations to distant galaxies. It also shows that large extinction corrections on Lyman break…
The detection of Ly alpha emission in star-forming galaxies in different shapes and intensities (always smaller than predicted for case B recombination) has puzzled the astronomical community for more than a decade. Here we use two dimensional calculations to follow the evolution of superbubbles and of the H II regions generated by the output of UV photons from massive stars. We show the impact caused by massive star formation in the ISM of different galaxies and we look at the conditions required to detect Ly alpha emission from a nuclear H II region, and the variety of profiles that may be e…
We present accurate Monte-Carlo calculations of Lyman Alpha (hereafter Lya) radiation pressure in a range of models which represent galaxies during various epochs of our Universe. We show that the radiation force that Lya photons exert on hydrogen gas in the neutral intergalactic medium (IGM), that surrounds minihalos that host the first stars, may exceed gravity by orders of magnitude and drive supersonic winds. Lya radiation pressure may also dominate over gravity in the neutral IGM that surrounds the HII regions produced by the first galaxies. However, the radiation force is likely too weak…
We test the hypothesis that the host galaxies of long-duration gamma-ray bursts (GRBs) as well as quasar-selected damped Lyman-alpha (DLA) systems are drawn from the population of UV-selected star-forming, high-z galaxies (generally referred to as Lyman-break galaxies). Specifically, we compare the metallicity distributions of the GRB and DLA populations to simple models where these galaxies are drawn randomly from the distribution of star-forming galaxies according to their star-formation rate and HI cross-section respectively. We find that it is possible to match both observational distribut…
We present the first spectroscopic measurement of the spatial cross-correlation function between damped Lyman alpha systems (DLAs) and Lyman break galaxies (LBGs). We obtained deep u'BVRI images of nine QSO fields with 11 known z ~ 3 DLAs and spectroscopically confirmed 211 R < 25.5 photometrically selected z > 2 LBGs. We find strong evidence for an overdensity of LBGs near DLAs versus random, the results of which are similar to that of LBGs near other LBGs. A maximum likelihood cross-correlation analysis found the best fit correlation length value of r_0 = 2.9^(+1.4)_(-1.5) h^(-1)Mpc using a …
We report an ultra-high-resolution simulation that follows evolution from the earliest stages of galaxy formation through the period of dynamical relaxation. The bubble structures of gas revealed in our simulation ($< 3\times 10^8$ years) resemble closely the high-redshift Lyman $α$ emitters (LAEs). After $10^9$ years these bodies are dominated by stellar continuum radiation and look like the Lyman break galaxies (LBGs) known as the high-redshift star-forming galaxies at which point the abundance of elements appears to be solar. After $1.3\times10^{10}$ years, these galaxies resemble present-d…
In this contribution we briefly describe our recent results on the properties of Lyman break galaxies at z~5 obtained from deep and wide blank field surveys using Subaru telescope, and through the comparison with samples at lower redshift ranges we discuss the evolution of star-forming galaxies in the early universe.
We briefly summarize our findings from the unbiased surveys for $z$$\sim$5 LBGs based on Subaru/Suprime-Cam and follow-up optical spectroscopy.
We report a deficiency of luminous Lyman break galaxies (LBGs) with a large rest-frame equivalent width (EW_rest) of Lyman-alpha emission at z~5-6. Combining our spectroscopic sample of LBGs at z~5 and those from the literature, we found that luminous LBGs at z~5-6 generally show weak Lyman-alpha emissions, while faint LBGs show a wide range of Lyman-alpha EW_rest and tend to have strong (EW_rest >20A) Lyman-alpha emissions; i.e., there is a deficiency of strong Lyman-alpha emission in luminous LBGs. There seems to be a threshold UV luminosity for the deficiency; it is M_1400 = -21.5 \~ -21.0 …
We present the faintest spectroscopically confirmed sample of redshift four and five Lyman break galaxies to date. The sample is based on slitless grism spectra of the Hubble Ultra Deep Field region from the GRAPES (Grism ACS Program for Extragalactic Science) and PEARS (Probing Evolution and Reionization Spectroscopically) projects, using the G800L grism on the HST Advanced Camera for Surveys. We report here confirmations of 39 galaxies, pre-selected as candidate Lyman break galaxies using photometric selection criteria. We compare a "traditional" V-dropout selection to a more liberal one (wi…
We use deep HST STIS and NICMOS images of three spectroscopically confirmed galaxy counterparts of high-redshift damped Ly-alpha (DLA) absorbers (one of which is a new discovery) to test the hypothesis that high-redshift DLA galaxies are Lyman-break galaxies. If this hypothesis is correct the emission properties of DLA galaxies must lie within the range of emission properties measured for Lyman-break galaxies of similar absolute magnitude. This will be true regardless of selection biases in the sample of detected DLA galaxies. We test this prediction using several emission properties: half-lig…
We summarise the main results of recent work on the Lyman break galaxy population which takes advantage of newly commissioned instrumentation on the VLT and Keck telescopes to push the detection of these objects to new wavelengths and more sensitive limits. We focus in particular on near-infrared observations targeted at detecting emission lines of [O II], [O III], and H-beta and on the first tentative detection of Lyman continuum emission from star forming galaxies at z = 3.
We use deep GALEX images of CDFS in UV to define the first large sample of 420 Lyman Break Galaxies at z~1. We use a PSF fitting to estimate UV magnitudes on these deep crowded images. Deep Spitzer IRAC and MIPS provide the first detection of a large sample of Lyman Break Galaxies in the mid- to far-infrared range. We are therefore able to study and compare the UV and TIR emission of Lyman Break Galaxies. We find that about 15% of the LBG sample are strong emitters at 24 microns (Red LBGs). Most of them are Luminous IR Galaxies (LIRGs) while the rest (Blue LBGs) are undetected at the 83 microJ…
We report on the status of large surveys of photometrically selected star forming galaxies at z~3 and z~4, with particular emphasis on both the advantages and the limitations of selecting objects using the ``Lyman break'' technique. Current results on the luminosity functions, luminosity densities, color distribution, star formation rates, clustering properties, and the differential evolution of the population as a function of redshift are summarized.
We have measured the counts-in-cells fluctuations of 268 Lyman-break galaxies with spectroscopic redshifts in six 9 arcmin by 9 arcmin fields at z~3. The variance of galaxy counts in cubes of comoving side length 7.7, 11.9, 11.4 h^{-1} Mpc is σ_{gal}^2 ~ 1.3\pm0.4 for Ω_M=1, 0.2 open, 0.3 flat, implying a bias on these scales of σ_{gal} / σ_{mass} = 6.0\pm1.1, 1.9\pm0.4, 4.0\pm0.7. The bias and abundance of Lyman-break galaxies are surprisingly consistent with a simple model of structure formation which assumes only that galaxies form within dark matter halos, that Lyman-break galaxies' rest-U…
Broadband optical and IR spectral energy distributions are determined for spectroscopically confirmed z>2 Lyman break objects in the Hubble Deep Field (HDF). These photometric data are compared to spectral synthesis models which take into account the effects of metallicity and of internal reddening due to dust. It is found that, on average, Lyman break objects are shrouded in enough dust (typically E(B-V)~0.3) to suppress their UV fluxes by a factor of more than 10. The dust-corrected star formation rate in a typical HDF Lyman break object is ~60 h^-2 M_sun/yr (q_0=0.5). Furthermore, these obj…
Using the UVES echelle spectrograph at the ESO VLT we obtained high-resolution (R = 40 000) spectra of the object SDSS J1553+0056, which has been identified in the literature alternatively as a high-redshift quasar or as a Lyman-break galaxy (LBG). Although low-resolution spectra of SDSS J1553+0056 closely resemble those of LBGs, our high-resolution spectra allow us to identify this object unambiguously as a LoBAL quasar, probably belonging to the rare FeLoBALQSO class. Based on our spectrum we discuss how misidentifications of such objects from low-resolution spectra can be avoided.
We discuss the spectral character of Lyman-limit-selected, star-forming galaxies at z>3. The rest-frame UV spectra of these faint galaxies may show Ly-alpha in either absorption or emission, probably depending upon their local ISM content and geometry. Other UV interstellar resonance absorption lines show considerable variation in strength, likely related to differences in the galactic metal abundances. We present initial results on B-drop galaxies, generally at z~4. Our low-resolution spectrograms show no measurable flux below the redshifted Lyman limit (912 Angstroms). Thus, it is likely tha…
Motivated by the observed discrepancy between the strong spatial correlations of Lyman break galaxies (LBGs) and their velocity dispersions, we consider a theoretical model in which these starbursting galaxies are associated with dark matter halos that experience appreciable infall of material. We show using numerical simulation that selecting halos that substantially increase in mass within a fixed time interval introduces a ``temporal bias'' which boosts their clustering above that of the underlying population. If time intervals consistent with the observed LBGs star formation rates of 50 so…
We have carried out targetted sub-mm observations as part of a programme to explore the connection between the rest-frame UV and far-IR properties of star-forming galaxies at high redshift, which is currently poorly understood. On the one hand the Lyman break technique is very effective at selecting z~3 galaxies. On the other hand `blank field' imaging in the sub-mm seems to turn up sources routinely, amongst which some are star forming galaxies at similar redshifts. Already much work has been done searching for optical identifications of objects detected using the SCUBA instrument. Here we ha…
Thomson scattering of the Cosmic Microwave Background (CMB) on moving electrons in the outflows of Lyman Break Galaxies (LBGs) at redshifts 2-8 contributes to the small-scale CMB anisotropies. The net effect produced by each outflow depends on its level of deviation from spherical symmetry, caused either by an anisotropic energy injection from the nuclear starburst or quasar activity, or by an inhomogeneous intergalactic environment. We find that for plausible outflow parameters consistent with spectroscopic observations of LBGs, the induced CMB anisotropies on arcminute scales reach up to $\s…
We present results from stacking analyses, using the 1 Ms Chandra Deep Field North data, that constrain the X-ray emission of Lyman break galaxies at z = 2-4. Stacking the counts from 24 individually undetected Lyman break galaxies located within the Hubble Deep Field North, we have obtained average detections of these objects in the resulting 0.5-8.0 keV and 0.5-2.0 keV images; these images have effective exposure times of 22.4 Ms (260 days). Monte Carlo testing empirically shows the detections to be highly significant. The average rest-frame 2-8 keV luminosity of a Lyman break galaxy is deri…
We present the results of detailed studies of the astrophysical conditions in z~3 Lyman Break Galaxies (LBGs), placing particular emphasis on what is learned from LBG rest frame UV spectra. By drawing from our database of ~1000 spectra, and constructing higher S/N composite spectra from galaxies grouped according to properties such as luminosity, extinction, morphology, and environment, we can show how the rest-frame UV spectroscopic properties systematically depend on other galaxy properties. Such information is crucial to understanding the detailed nature of LBGs, and their impact on the sur…
Using the IRAM Plateau de Bure Interferometer, we have searched for CO(3-2) emission from the dusty Lyman break galaxy Westphal-MD11 at z = 2.98. Our sensitive upper limit is surprisingly low relative to the system's 850 um flux density and implies a far-IR/CO luminosity ratio as elevated as those seen in local ultraluminous mergers. We conclude that the observed dust emission must originate in a compact structure radiating near its blackbody limit and that a relatively modest molecular gas reservoir must be fuelling an intense nuclear starburst (and/or deeply buried active nucleus) that may h…
We present deep Hubble Space Telescope ACS and NICMOS images of six bright Lyman-break galaxy candidates that were previously discovered in the Sloan Digital Sky Survey. We find that five of the objects are consistent with unresolved point sources. Although somewhat atypical of the class, they are most likely LoBAL quasars, perhaps FeLoBALs. The sixth object, J1147, has a faint companion galaxy located ~0.8 arcsec to the southwest. The companion contributes ~8% of the flux in the observed-frame optical and infrared. It is unknown whether this companion is located at the same redshift as J1147.
Near-infrared observations of Lyman-break galaxies at redshifts z~3 are beginning to provide constraints on ages, star-formation histories, dust content, metallicities, and stellar masses. At present, uncertainties of more than an order of magnitude are typical for many of these parameters. It is nonetheless interesting to ask what the stellar-population models imply for the existence and luminosities of Lyman-break galaxies at higher redshift. To this end we examine the inferred star-formation rates in two well-studied samples of galaxies as a function of redshift out to z = 10 for various be…
We investigate the nature of Lyman break galaxies (LBGs) using a chemodynamical model for evolution of galaxies. Our models predict an early (the first Gyr) stage of intense star formation in the evolution of massive spheroids which could be identified to the LBGs, observed at redshift $\sim 3$ with strong ongoing star formation. In particular, we are successful in reproducing the properties of the LBG DSF 2237+116 C2 with a model describing a young $\sim L^*$ spheroid. The comparison of the predictions of our models with the observations gives support to the scenario in which LBGs are the pro…
We present the results of a high resolution UV 2-D spectroscopic survey of star forming galaxies observed with HST-STIS. Our main aim was to map the Lyman alpha profiles to learn about the gas kinematics and its relation with the escape of Lyman alpha photons and to detect extended Lyman alpha emission due to scattering in gaseous halos. We have combined our data with previously obtained UV spectroscopy on other three star-forming galaxies. We find that the P-Cygni profile is spatially extended, smooth and spans several kiloparsecs covering a region much larger than the starburst itself. We pr…
We present the first rest-frame ~4 micron detection of a Lyman break galaxy. The data were obtained using the 16 micron imaging capability of the Spitzer Infrared Spectrograph. The target object, J134026.44+634433.2, is an extremely luminous Lyman break galaxy at z=2.79 first identified in Sloan Digital Sky Survey spectra (Bentz, Osmer, & Weinberg 2004). The source is strongly detected with a flux of 0.94 +/- 0.02 mJy. Combining Spitzer and SDSS photometry with supporting ground-based J- and K-band data, we show that the spectral energy distribution is consistent with an actively star-forming …
We perform cosmological simulations of galaxies forming at z=3 using the hydrodynamics grid code, Enzo. By selecting the largest galaxies in the volume to correspond to Lyman-break galaxies, we construct observational spectra of the HI flux distribution around these objects, as well as column densities of CIV and OVI throughout a refined region. We successfully reproduce the most recent observations of the mean HI flux in the close vicinity of Lyman-break galaxies but see no evidence for the proximity effect in earlier observations. While our galaxies do return metals to the IGM, their quantit…
We present the results of rest-frame ultraviolet spectroscopic observations of a sample of 14 z~3 star-forming galaxies in the SSA22a field. These spectra are characterized by unprecedented depth in the Lyman-continuum region. For the first time, we have detected escaping ionizing radiation from individual galaxies at high redshift, with two of the 14 objects showing significant emission below the Lyman limit. We also measured the ratio of emergent flux density at 1500 AA to that in the Lyman-continuum region, for the individual detections (C49 and D3) and the sample average. If a correction f…
(abridged) We present a large sample of z~3 U- band dropout galaxies extracted from the Canada-France deep fields survey (CFDF). Our catalogue covers an effective area of ~1700 arcmin^2 divided between three large, contiguous fields separated widely on the sky. To IAB=24.5, the survey contains 1294 Lyman-break candidates, in agreement with previous measurements by other authors. Based on comparisons with spectroscopic observations and simulations, we estimate that our sample of Lyman-break galaxies is contaminated by stars and interlopers at no more than ~30%. We find that ω(θ) is well fitted …
Motivated by an interpretation of $z \sim 3$ objects by Jimenez and Haiman (2006), we examine processes that control the fraction of primordial ($Z = 0$) gas, and so primordial stars, in high-SFR Lyman break galaxies. A primordial fraction different from 1 or 0 requires microscopic diffusion catalyzed by a velocity field with timescale comparable to the duration of star formation. The only process we found that satisfies this requirement for LBGs without fine-tuning is turbulence-enhanced mixing induced by exponential stretching and compressing of metal-rich ejecta. The time-dependence of the …
We detect 1.2mm continuum emission from dust in the gravitationally lensed Lyman break galaxy MS 1512+36-cB58. Our detected flux is surprisingly low: relative to local starburst galaxies, cB58 appears to produce somewhat less far-IR emission than its UV reddening predicts. After comparing several different estimates of the source's dust content, we conclude that the apparent discrepancy is most likely related to uncertainty in its UV spectral slope. Alternate scenarios to account for a far-IR "deficit" which rely on a high dust temperature or differential magnification are less satisfactory. O…
We have measured the rest--frame lambda~1500 Ang comoving specific luminosity density of star--forming galaxies at redshift 3.5<z<6.5 from deep images taken with the Hubble Space Telescope (HST)and the Advanced Camera for Surveys (ACS), obtained as part of the Great Observatories Origins Deep Survey (GOODS). We used color selection criteria to construct samples of star--forming galaxies at redshifts z~4, 5 and 6, identified by the signature of the 912 Ang Lyman continuum discontinuity and Lyman-alpha forest blanketing in their rest--frame UV colors (Lyman--break galaxies). The ACS samples cove…
With SIRTF and NGST in the offing, it is interesting to examine what the stellar populations of z~3 galaxies models imply for the existence and nature of Lyman-break galaxies at higher redshift. To this end, we ``turn back the clock'' on the stellar population models that have been fit to optical and infrared data of Lyman-break galaxies at z~3. The generally young ages (typically 10^8 +- 0.5 yr) of these galaxies imply that their stars were not present much beyond z=4. For smooth star-formation histories SFR(t) and Salpeter IMFs, the ionizing radiation from early star-formation in these galax…
The optical properties of a number of supercompact ultraviolet luminous galaxies (UVLG), recently discovered in the local Universe matching GALEX and Sloan Digital Sky Survey (SDSS) data, are discussed. Detailed re-analysis of the SDSS data for these and other similar but nearer galaxies shows that their surface brightness radial profile in both R and u bands is in most cases well described by an extended disk plus a central unresolved component (possibly a bulge). Since the SDSS pipeline used a single disk component to derive the half light radius of these UVLGs their size was severely undere…
We present the results of Spectral Energy Distribution (SED) fitting analysis for Lyman Break Galaxies (LBGs) at $z\sim5$ in the GOODS-N and its flanking fields. From the SED fitting for $\sim100$ objects, we found that the stellar masses range from $10^{8}$ to $10^{11}M_{\odot}$ with a median value of $4\times10^{9}M_{\odot}$. By using the large sample of galaxies at $z\sim5$, we construct the stellar mass function (SMF) with incompleteness corrections. By integrating down to $10^{8}M_{\odot}$, the cosmic stellar mass density at $z\sim5$ is calculated to be $7\times10^{6}M_{\odot}\textrm{Mpc}…
We calculate the statistical clustering of Lyman-break galaxies predicted in a selection of currently-fashionable structure formation scenarios. These models are all based on the cold dark matter model, but vary in the amount of dark matter, the initial perturbation spectrum, the background cosmology and in the presence or absence of a cosmological constant term. If Lyman-break galaxies form as a result of hierarchical merging, the amplitude of clustering depends quite sensitively on the minimum halo mass that can host such a galaxy. Interpretation of the recent observations by Giavalisco et a…
We fit general relativistic, geometrically thin accretion disk models with non-LTE atmospheres to near simultaneous multiwavelength data of 3C~273, extending from the optical to the far ultraviolet. Our model fits show no flux discontinuity associated with a hydrogen Lyman edge, but they do exhibit a spectral break which qualitatively resembles that seen in the data. This break arises from relativistic smearing of Lyman emission edges which are produced locally at tens of gravitational radii in the disk. We discuss the possible effects of metal line blanketing on the model spectra, as well as …
What type of objects are being detected as $z\sim 3$ "Lyman break galaxies"? Are they predominantly the most massive galaxies at that epoch, or are many of them smaller galaxies undergoing a short-lived burst of merger-induced star formation? We attempt to address this question using high-resolution cosmological hydrodynamic simulations including star formation and feedback. Our $Λ$CDM simulation, together with Bruzual-Charlot population synthesis models, reproduces the observed number density and luminosity function of Lyman break galaxies when dust is incorporated. The inclusion of dust is c…
A large population of z>5 Lyman break galaxies has been identified in recent years. However, the high redshift galaxies selected by different surveys are subject to a variety of selection effects - some overt, others more subtle. We present an analysis of sample completeness and contamination issues in high redshift surveys, focusing on surveys at z=5 and using a spectroscopically-confirmed low redshift sample from the DEEP2 survey in order to characterise contaminant galaxies. We find that most surveys underestimate their contamination from highly clustered galaxies at z=1 and stars. We consi…
In 2000, we started the program ``Building the Bridge between Damped Ly-alpha Absorbers and Lyman-Break Galaxies: Ly-alpha Selection of Galaxies'' at the European Southern Observatory's Very Large Telescope. This project is an attempt to use Ly-alpha selection of high-z galaxies to bridge the gap between absorption- and emission-selected galaxies by creating a large database of z=3 galaxies belonging to the abundant population of faint (R>25.5) galaxies probed by the Damped Ly-alpha Absorbers (DLAs). Here we present the first results of our program, namely the results from a deep Ly-alpha stud…
The Aim of our study is to understand the variety of observed Lyman-alpha (Lya) line profiles and strengths in Lyman Break Galaxies (LBGs) and Lya emitters (LAEs), the physical parameters governing them, and hence deriving constraints on the gas and dust content and stellar populations of these objects. Using our 3D Lya radiation transfer code including gas and dust (Verhamme et al. 2006), we fit 11 LBGs from the FORS Deep Field with redshifts between 2.8 and 5 observed by Tapken et al. (2007). A simple geometry of a spherically expanding shell of HI is adopted. RESULTS : The variety of observ…
We report the first observations of the clustering environment of damped Lyman alpha absorption systems at z=4. Color selection and photometric redshifts were used to select 44 candidate Lyman-break galaxies brighter than I_AB=25.5 from deep BRI images of the 35 sq. arcmin field containing the quasar BR 0951-04. Multislit spectroscopy of 35 candidate galaxies was performed and 8 of these candidates have been confirmed as z>3.5 Lyman-break galaxies. With only BRI photometry, the photometric redshifts are quite accurate for the spectroscopically confirmed galaxies but have a high rate of misclas…
Using a combination of deep MID-IR observations obtained by IRAC, MIPS and IRS on board Spitzer we investigate the MID-IR properties of Lyman Break Galaxies (LBGs) at z~3, establish a better understanding of their nature and attempt a complete characterisation of the population. With deep mid-infrared and optical observations of ~1000 LBGs covered by IRAC/MIPS and from the ground respectively, we extend the spectral energy distributions (SEDs) of the LBGs to mid-infrared. Spitzer data reveal for the first time that the mid-infrared properties of the population are inhomogeneous ranging from th…
We summarise the results of a deep search for Lyman alpha emission from star-forming regions associated with damped Lyman alpha absorption systems and conclude that the Lyman alpha luminosity of high redshift galaxies is generally less than 10^(42) erg/s . We also present a newly discovered case, in the field of the QSO Q2059-360, where the emission is unusually strong, possibly because the damped system is close in redshift to the QSO.
We have compared the results from a model for the chemical evolution of an elliptical galaxy with initial luminous mass of 2x10^10 M_sun and effective radius of 2 kpc with the recent abundance determinations for the Lyman-break galaxy MS 1512-cB58 at a redshift z=2.7276. After correcting the iron abundance determination for the presence of dust we concluded that the observed [Si/Fe], [Mg/Fe], [N/Fe] are consistent with our model when a galactic age between 20 and 35 Myr is assumed. Moreover, the [N/O] ratio also suggests the same age. This age is in very good agreement with other independent s…
We report the discovery of a z~9 Lyman Break Galaxy (LBG) candidate, selected from the NICMOS Parallel Imaging Survey as a J-dropout with J110 - H160 = 1.7. Spitzer/IRAC photometry reveals that the galaxy has a blue H160 - 3.6 um color, and a spectral break between 3.6 and 4.5 um. We interpret this break as the Balmer break, and derive a best-fit photometric redshift of z~9. We use Monte Carlo simulations to test the significance of this photometric redshift, and show a 96% probability of z>7. We estimate a lower limit to the comoving number density of such galaxies at z~9 of phi > 3.8 x 10^{-…
We perform a detailed analysis of the statistical significance of a concentration of Lyman break galaxies at $z \sim 3$ recently discovered by Steidel et al. (1997), using a series of N-body simulations with $N=256^3$ particles in a $(100\himpc)^3$ comoving box. While the observed number density of Lyman break galaxies at $z\sim3$ implies that they correspond to systems with dark matter halos of $\simlt 10^{12}M_\odot$, the resulting clustering of such objects on average is not strong enough to be reconciled with the concentration if it is fairly common; we predict one similar concentration ap…
We derive the bolometric to X-ray correlation for a local sample of normal and starburst galaxies and use it, in combination with several UV reddening schemes, to predict the 2--8 keV X-ray luminosity for a sample of 24 Lyman-break galaxies in the HDF/CDF-N. We find that the mean X-ray luminosity, as predicted from the Meurer UV reddening relation for starburst galaxies, agrees extremely well with the Brandt stacking analysis. This provides additional evidence that Lyman-break galaxies can be considered as scaled-up local starbursts and that the locally derived starburst UV reddening relation …
The formation rate of luminous galaxies seems to be roughly constant from z~2 to z~4 from the recent observations of Lyman break galaxies (LBGs) (Steidel et al 1999). The abundance of luminous quasars, on the other hand, appears to drop off by a factor of more than twenty from z~2 to z~5 (Warren, Hewett, & Osmer 1994; Schmidt, Schneider, & Gunn 1995). The difference in evolution between these two classes of objects in the overlapping, observed redshift range, z=2-4, can be explained naturally, if we assume that quasar activity is triggered by mergers of luminous LBGs and one quasar lifetime is…
We explore empirical relations between three different populations of high-redshift galaxies and their hosting dark halos employing the halo model approach. Specifically we consider Lyman-break galaxies at z\sim4 and at z\sim5, and Lyman-Alpha emitters at z\simeq 4.86. We adopt a halo occupation function prescription to parameterize the properties of their hosting halos and the efficiency of halo-dependent star formation. We find that the two LBG samples are well described by the halo model with an appropriate HOF. We obtain constraints on properties of their hosting halos. A typical mass of h…
Measurements of [OIII] emission in Lyman Break galaxies (LBGs) at z>3 are presented. Four galaxies were observed with narrow-band filters using the Near-IR Camera on the Keck I 10-m telescope. A fifth galaxy was observed spectroscopically during the commissioning of NIRSPEC, the new infrared spectrometer on Keck II. The emission-line spectrum is used to place limits on the metallicity. Comparing these new measurements with others available from the literature, we find that strong oxygen emission in LBGs may suggest sub-solar metallicity for these objects. The [OIII]5007 line is also used to es…
We have selected 14 J-dropout Lyman Break Galaxy (LBG) candidates with J110 - H160 > 2.5 from the NICMOS Parallel Imaging Survey. This survey consists of 135 square arcminutes of imaging in 228 independent sight lines, reaching average 5 sigma sensitivities of J110 = 25.8 and H160 = 25.6 (AB). Distinguishing these candidates from dust reddened star forming galaxies at z ~ 2-3 is difficult, and will require longer wavelength observations. We consider the likelihood that any J-dropout LBGs exist in this survey, and find that if L*(z=9.5) is significantly brighter than L*(z=6) (a factor of four),…
We recently reported the discovery of FORJ0332-3557, a lensed Lyman-break galaxy at z=3.77 in a remarkable example of strong galaxy-galaxy gravitational lensing. We present here a medium-resolution rest-frame UV spectrum of the source, which appears to be similar to the well-known Lyman-break galaxy MS1512-cB58 at z=2.73. The spectral energy distribution is consistent with a stellar population of less than 30 Ma, with an extinction of A(V)=0.5 mag and an extinction-corrected star formation rate SFR(UV) of 200-300 Msun/a. The Lyman-alpha line exhibits a damped profile in absorption produced by …
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