Lyman-break Galaxy Candidates Research Articles

A Search for Lyman Break Galaxies at z > 8 in the NICMOS Parallel Imaging Survey

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), then a few J-dropout LBGs are likely. A similar increase in luminosity has been suggested by Eyles et al. and Yan et al., but the magnitude of this increase is uncertain.

The discovery of a significant sample of massive galaxies at redshifts 5 < z < 6 in the UKIDSS Ultra Deep Survey early data release

We have exploited the large area coverage of the combined UKIDSS Ultra Deep Survey (UDS) and Subaru/XMM-Newton Deep Survey (SXDS) to search for bright Lyman-break galaxies (LBGs) at z >= 5. Using the available optical+near-infrared photometry to efficiently exclude low-redshift contaminants, we identify nine z >= 5 LBG candidates brighter than z'=25(AB) within the 0.6 square degree overlap region between the UDS early data release (EDR) and the optical coverage of the SXDS. Accounting for selection incompleteness, we estimate the corresponding surface density of z >= 5 LBGs with z' ~5x10^10 Msun which, if confirmed, places them amongst the most massive galaxies currently known at z >= 5. It is found that Lambda CDM structure formation can produce sufficient numbers of dark matter halos at z >= 5 to accommodate our estimated number density of massive LBGs for plausible values of sigma_8 and the ratio of stellar to dark matter. Moreover, it is found that recent galaxy formation models can also account for the existence of such massive galaxies at z >= 5. Finally, no evidence is found for the existence of LBGs with stellar masses in excess of ~3x10^11 Msun at this epoch, despite the large co-moving volume surveyed.

HST/ACS observations of Lyman‐break galaxies and Lyα emitters associated with radio galaxies at z > 4

AbstractDistant radio galaxies may pinpoint overdense regions in the early universe.We have collected data with HST/ACS towards several overdensities of Lyα emitters associated with radio galaxies discovered by Venemans et al. Using the Lyman break selection technique we find statistical evidence for additional galaxies associated with the radio galaxies TN J1338–1942 at z = 4.1 and TN J0924–2201 at z = 5.2. In the case of TN J1338–1942, the angular distribution of candidate Lyman break galaxies is highly filamentary across the ∼12 arcmin2 field, with more than half of the objects clustered in a 4.4 arcmin2 region that includes the radio galaxy. Both fields appear to be significantly richer in Lyman break galaxies than the Great Observatories Origins Deep Survey (GOODS) fields, suggesting that the radio galaxies are embedded in galaxy groups or (forming) clusters. The Lyman break galaxies have mild to moderate star formation rates and relatively blue UV continuum colours. Except for their high equivalent width Lyα , the properties of spectroscopically confirmed Lyα emitters associated with these radio galaxies are consistent with those of normal Lyman break galaxies at relatively low luminosities. The two radio galaxies have some intriguing properties: TN J1338–1942 is extremely bright in the rest‐frame UV, and has a highly disturbed morphology presumed to arise from interactions between the jet and the surrounding medium, and a starburst‐driven superwind. The UV star formation rate and (projected) size of TN J0924–2201 are typical of relatively faint Lyman break galaxies at z ∼ 3–5. Yet it is a luminous, radio‐loud AGN, suggesting the presence of a supermassive black hole that may have acquired its mass before the host galaxy produced the bulk of its stars. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The Multiwavelength Survey by Yale‐Chile (MUSYC): Survey Design and Deep Public UBVRI z ′ Images and Catalogs of the Extended Hubble Deep Field–South

We present UBVRIz' optical images taken with MOSAIC on the CTIO 4 m telescope of the 0.32 deg2 Extended Hubble Deep Field-South. This is one of four fields comprising the MUSYC survey, which is optimized for the study of galaxies at z = 3, active galactic nucleus (AGN) demographics, and Galactic structure. Our methods used for astrometric calibration, weighted image combination, and photometric calibration in AB magnitudes are described. We calculate corrected aperture photometry and its uncertainties and find through tests that these provide a significant improvement upon standard techniques. Our photometric catalog of 62,968 objects is complete to a total magnitude of RAB = 25, with R-band counts consistent with results from the literature. We select z 3 Lyman break galaxy (LBG) candidates from their UVR colors and find a sky surface density of 1.4 arcmin-2 and an angular correlation function w(θ) = (2.3 ± 1.0)θ-0.8, consistent with previous findings that high-redshift Lyman break galaxies reside in massive dark matter halos. Our images and catalogs are available online.

Rest-frame optical and far-infrared observations of extremely bright Lyman-break galaxy candidates atz∼ 2.5

We have investigated the rest-frame optical and far-infrar ed properties of a sample of extremely bright candidate Lyman-break galaxies (LBG) identified in the Sloan Digital Sky Survey. Their high ultraviolet luminosities and lack of str ong ultraviolet emission lines are suggestive of massive starbursts, although it is possible t hat they are more typical luminosity LBGs which have been highly magnified by strong gravitationa l lensing. Alternatively, they may be an unusual class of weak-lined quasars. If the ultraviolet and submillimetre properties of these objects mirror those of less luminous, starbur st LBGs, then they should have detectable rest-frame far-infrared emission. However, our submm photometry fails to detect such emission, indicating that these systems are not merely scaled-up (either intrinsically or as a result of lensing) examples of typical LBGs. In addition we have searched for the morphological signatures of strong lensing, using high-resol ution, near-infrared imaging, but we find none. Instead, near-infrared spectroscopy reveals tha t these systems are, in fact, a rare class of broad absorption-line (BAL) quasars.

Number Density of Bright Lyman-Break Galaxies at z ∼ 6 in the Subaru Deep Field

Abstract We report on bright Lyman-break galaxies (LBGs) selected in a $767 \,\mathrm{arcmin}^2$ area of the Subaru Deep Field. The selection was made in the $i-z_{\mathrm{R}}$ versus $z_{\mathrm{B}}-z_{\mathrm{R}}$ plane, where $z_{\mathrm{B}}$ and $z_{\mathrm{R}}$ are new bandpasses with a central wavelength of 8842 Å and 9841 Å, respectively. We detected 12 LBG candidates down to $z_{\mathrm{R}} = 25.4$, and calculated the normalization of the rest-frame far-ultraviolet (FUV: $\simeq 1400 \,{Å}$) luminosity function at $M_{\mathrm{FUV}} =-21.6$ to be $\phi(-21.6) = (2.6 \pm 0.7) \times 10^{-5} \,\mathrm{mag}^{-1} \,\mathrm{Mpc}^{-3}$. This must be the most reliable measurement ever obtained of the number density of bright $z\sim 6$ LBGs, because it is more robust against both contamination and cosmic variance than previous values. The FUV luminosity density contributed from LBGs brighter than $M_{\mathrm{FUV}} =-21.3$ is $(2.8 \pm 0.8) \times 10^{24} \,\mathrm{erg} \,\mathrm{s}^{-1} \,\mathrm{Hz}^{-1} \,\mathrm{Mpc}^{-3}$, which is equivalent to a star-formation rate density of $(3.5 \pm 1.0) \times 10^{-4} \,{{{M}_{\odot}}} \,\mathrm{yr}^{-1} \,\mathrm{Mpc}^{-3}$. We find that the FUV luminosity density of bright galaxies increases by an order of magnitude from $z\sim 6$ to $\sim 3$, and then drops by $10^3$ from $z \sim 3$ to the present epoch. The evolutionary behavior of bright LBGs resembles that of luminous dusty star-forming galaxies and bright QSOs. The redshift of $z \sim 3$ appears to be a remarkable era in the cosmic history when massive galaxies were being intensively formed.

Z~6 i-DROPOUT GALAXIES IN THE SUBARU /XMM-NEWTON DEEP FIELD

We conducted an extremely wide field survey of z 6 Lyman break galaxies (LBGs) to precisely derive their bright end surface density overcoming the bias due to cosmic variance. We selected out LBG candidates in the Subaru/ XMM-Newton Deep Survey Field (SXDS) over the total of sky area down to $z_{AB}

Survey for Galaxies Associated withz∼ 3 Damped Lyα Systems. I. Spectroscopic Calibration ofu′BVRIPhotometric Selection

We present a survey of z ~ 3 Lyman break galaxies (LBGs) associated with damped Lyα systems (DLAs) with the primary purpose of determining the DLA-LBG cross-correlation. This paper describes the acquisition and analysis of imaging and spectroscopic data of nine quasar fields having 11 known z ~ 3 DLAs covering an area of 465 arcmin2. Using deep u'BVRI images, 796 LBG candidates up to an apparent RAB magnitude of 25.5 were photometrically selected from 17,343 sources detected in the field. Spectroscopic observations of 529 LBG candidates using the Keck Low Resolution Imaging Spectrometer yielded 339 redshifts. We have conservatively identified 211 z > 2 objects with z = 3.02 ± 0.32. We discuss our method of z ~ 3 LBG identification and present a model of the u'BVRI photometric selection function. We use the 339 spectra to evaluate our u'BVRI z ~ 3 Lyman break photometric selection technique.

Deep Mid‐Infrared Observations of Lyman Break Galaxies

As part of the in-orbit checkout activities for the Spitzer Space Telescope, the Infrared Array Camera (IRAC) team carried out a deep observation (average integration time ~8 hr) of a field surrounding the bright QSO HS 1700+6416. This field contains several hundred z ~ 3 Lyman break galaxy (LBG) candidates, and we report here on their mid-infrared properties, including the IRAC detection rate, flux densities, and colors, and the results of fitting population synthesis models to the optical, near-infrared, and IRAC magnitudes. The results of the model fitting show that previous optical/near-infrared studies of LBGs were not missing large, hidden old stellar populations. The LBG candidates' properties are consistent with those of massive star-forming galaxies at z ~ 3. Other IRAC sources in the same field have similar properties, so IRAC selection may prove to be a promising method of finding additional high-redshift galaxies.

Bright Lyman-break galaxy candidates in the SDSS first data release

We discuss the discovery of six bright Lyman break galaxy candidates in the Sloan Digital Sky Survey and the follow-up observations necessary to determine whether they are powered by star formation or by active galactic nuclei.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Clustering of Galaxies atz ∼ 3 around the Probable Damped Lyα Absorber toward QSO APM 08279+5255

We present results on the clustering of Lyman break galaxies (LBGs) around a probable damped Ly? absorption line cloud (DLA) at zabs = 2.974 from deep UBVI images of the field containing the quasar APM 08279+5255 (zem = 3.91). The large area covered by our images, 0.31 deg2 or ~40 ? 40 Mpc comoving at redshift z = 3, and their depth, ?I,AB(sky) 27.6 mag arcsec-2, allow us to identify ~450 LBG candidates brighter than IAB = 24.80 at 2.75 < z < 3.25 both close (50 kpc) to the DLA line of sight and up to 20 Mpc (comoving) from the DLA, i.e., physically unrelated. LBG candidates were identified using photometric redshift techniques that include the I magnitude as a prior estimate in addition to the colors. The two are combined using Bayes's theorem. This helps to break the degeneracies that occur in a pure spectral template fitting scheme. The overall rms is ?z 0.15 at z ~ 3 based on our analysis of photometric redshifts in the HDF-N. From the redshift likelihood distributions, we selected LBG galaxies within a redshift slice of width Wz = 0.15( ?z) centered on the redshift of the DLA zabs. Within that redshift slice, we find an enhancement of galaxies near the DLA using both the surface density (?/?g 3) and an estimator of the three-dimensional spatial overdensity (n/g ~ 5 ? 3). The surface overdensity ?/?g is significant at the more than 95% significance level on scales 2.5 < r? < 5 Mpc comoving. The overdensity cannot be related to the QSO environment since the QSO is at zem = 3.91. These results imply that some DLA could reside in high-density regions. We search within 45'' from the line of sight for galaxies responsible for the DLA and find one candidate with zphot = 3.03 that is 26'' (145 kpc physical) away. From its magnitude I = 24.65 ? 0.2, its luminosity is MI,AB = -21.35. Due to its large impact parameter, however, this galaxy is not a likely candidate for the absorber.

Lyman Break Galaxies at z ∼ 5: Luminosity Function

Abstract We present the results of a search for Lyman break galaxies (LBGs) at $z \sim 5$ in a 618 square-arcmin field including the Hubble Deep Field-North (HDF-N) taken by the Subaru Prime Focus Camera. Utilizing the published redshift data of the HDF-N and its flanking fields, the color selection criteria were chosen so that LBGs could be picked out most efficiently and least contaminated by foreground objects. The numbers of detected LBG candidates were 96 in $23.0 \leq I_c \; (\mathrm{mag}) \leq 24.5$ and 310 in $23.0 \leq I_c \leq 25.5$. There is a hint of a deficiency of bright blue galaxies, although it is not as clear as has been suggested for LBGs at $z \sim 3$ to 4. With 305 LBG candidates in a 575 square-arcmin field, the rest-frame UV luminosity function of LBGs at $4.4 \lesssim z \lesssim 5.3$ was derived statistically by considering both the contamination by objects at the intermediate redshift and the incompleteness of the survey. The fraction of the contamination was estimated to be $\sim 50 \%$ in the faintest magnitude range. The completeness of the survey was $\sim 80\%$ at the bright part of the sample, and $\sim 20\%$ in the faintest magnitude range ($25.0 &amp;lt; I_c \leq 25.5$). The luminosity function of LBG candidates at $z \sim 5$ did not show a significant difference from those of LBGs at $z \sim 3$ and 4, though there might be a slight decrease in the fainter part. The UV luminosity density within the observational limit was 0.56–0.69 times smaller than that obtained for LBGs at $z \sim 3$, depending on the adopted cosmology and the integration range of the luminosity function. This decrease in the UV luminosity at $z \sim 5$ compared to that at $z \sim 3$ is due to the smaller number density of faint galaxies at $z \sim 5$. The similarity of the luminosity functions at redshifts 5 to 3 implies that most of the LBGs at $z \sim 5$ should have faded out at $z \sim 3$, and that the LBGs at $z \sim 5$ are different galaxies from those seen at $z \sim 3$, if we take the face values for the ages of the LBGs at $z \sim 3$ obtained by a SED fitting in which a continuous star formation in an individual galaxy was assumed. However, if the star formation in LBGs is sporadic, the similarity of the luminosity function at $z \sim 3$ and 5 would be explained. Such sporadic star formation has been suggested by hydrodynamical simulations and semi-analytic models with collisional starbursts, and the trend of the cosmic star formation history predicted by these studies resembles that estimated from an integration of the UV luminosity density within the observational limit.

First Investigation of the Clustering Environment of Damped Lyα Absorbers atz ≃ 4

We report the first observations of the clustering environment of damped Lyman α absorption systems at z 4. Color selection and photometric redshifts were used to select 44 candidate Lyman-break galaxies brighter than IAB = 25.5 from deep BRI images of the 35 arcmin2 field containing the quasar BR 0951-04. Multislit spectroscopy of 35 candidate galaxies was performed and eight 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 misclassification due to color degeneracies between Lyman-break galaxies and low-redshift ellipticals. Both of the z > 3.5 galaxies found within 15'' of the quasar line-of-sight appear to be causing absorption systems in the quasar spectrum. We use a battery of statistical tests to look for clustering in the redshift histogram of the z > 3.5 galaxies but do not find measurable clustering of these Lyman-break galaxies with the damped Lyα absorbers. With a larger sample of galaxies, our method should determine the cross-correlation between these objects, which probes the bias and hence the mass of the damped Lyα absorbers.

Clustering Properties of Galaxies at [CLC][ITAL]z[/ITAL][/CLC] ∼ 4 in the Subaru/[ITAL]XMM[/ITAL] Deep Survey Field

We study the clustering properties of about 1200 z ~ 4 Lyman break galaxy (LBG) candidates with i' < 26 that are selected by color from deep BRi' imaging data of a 618 arcmin2 area in the Subaru/XMM-Newton Deep Field taken with Subaru Prime Focus Camera. The contamination and completeness of our LBG sample are evaluated, on the basis of the Hubble Deep Field-North (HDF-N) objects, to be 17% and 45%, respectively. We derive the angular correlation function over θ = 2''-1000'' and find that it is fitted fairly well by a power law, ω(θ) = Aωθ-0.8, with Aω = 0.71 ± 0.26. We then calculate the correlation length r0 (in comoving units) of the two-point spatial correlation function ξ(r) = (r/r0)-1.8 from Aω using the redshift distribution of LBGs derived from the HDF-N and find that r0 = 2.7 h-1 Mpc in a Λ-dominated universe (Ωm = 0.3 and ΩΛ = 0.7). This is twice as large as the correlation length of the dark matter at z ≃ 4 predicted from an analytic model by Peacock and Dodds but about twice as small as that of bright galaxies predicted from a semianalytic model by Baugh and coworkers. We find an excess of ω(θ) on small scales (θ ≲ 5''), departing from the power-law fit by over 3 σ significance levels. Interpreting this as being due to galaxy mergers, we estimate the fraction of galaxies undergoing mergers in our LBG sample to be 3.0% ± 0.9%, which is significantly smaller than those of galaxies at intermediate redshifts.

Evidence for Galaxy Formation at High Redshift

Metcalfe et al. (1995, 1996) have shown that galaxy counts from the UV to the near-IR are well-fitted by simple evolutionary models where the space density of galaxies remains constant with look-back time while the star-formation rate rises exponentially. We now extend these results, first by using data from the Herschel Deep Field to show that these same models give detailed fits to the faint galaxy r - i : b - r colour-colour diagram. We then use these models to predict the number counts of high redshift galaxies detected by the Lyman break technique. At z ≈ 3 there is almost exact agreement between our prediction and the data, suggesting that the space density of galaxies at z ≈ 3 may be close to its local value. At z ≈ 4 the space density of bright galaxies remains unchanged; however, the space density of dwarf galaxies is significantly lower than it is locally, suggesting that we have detected an epoch of dwarf galaxy formation at z ≈ 4. Finally, significant numbers of Lyman-break galaxy candidates are also detected at z ≈ 6 in the Hubble and Herschel Deep Fields; taking this observation together with a number of recent detections of spectroscopically confirmed z ≈ 6 galaxies suggests that the space density of bright galaxies at z ≈ 6 remains comparable to the local space density, and thus that the epoch of formation of bright galaxies may lie at yet higher redshift.

WFPC2 Observations of the Hubble Deep Field South

The Hubble Deep Field-South observations targeted a high-galactic-latitude field near QSO J2233-606. We present WFPC2 observations of the field in four wide bandpasses centered at roughly 300, 450, 606, and 814 nm. Observations, data reduction procedures, and noise properties of the final images are discussed in detail. A catalog of sources is presented, and the number counts and color distributions of the galaxies are compared to a new catalog of the HDF-N that has been constructed in an identical manner. The two fields are qualitatively similar, with the galaxy number counts for the two fields agreeing to within 20%. The HDF-S has more candidate Lyman-break galaxies at z > 2 than the HDF-N. The star-formation rate per unit volume computed from the HDF-S, based on the UV luminosity of high-redshift candidates, is a factor of 1.9 higher than from the HDF-N at z ~ 2.7, and a factor of 1.3 higher at z ~ 4.