C. G. Lacey, C. M. Baugh, C. S. Frenk, A. J. Benson, .
备注：
26 pages, 18 figures. Accepted for publication in MNRAS. Revised in response to referee, main changes are more detailed discussion of dust extinction in S2.2 & S3.2.3, with new Fig.6
We make a detailed investigation of the properties of Lyman-break galaxies (LBGs) in the LambdaCDM model. We present predictions for two published variants of the GALFORM semi-analytical model: the Baugh et al. (2005) model, which has star formation at high redshifts dominated by merger-driven starbursts with a top-heavy IMF, and the Bower et al. (2006) model, which has AGN feedback and a standard Solar neighbourhood IMF throughout. We show predictions for the evolution of the rest-frame far-UV luminosity function in the redshift range z=3-20, and compare with the observed luminosity functions of LBGs at z=3-10. We find that the Baugh et al. model is in excellent agreement with these observations, while the Bower et al. model predicts too many high-luminosity LBGs. Dust extinction, which is predicted self-consistently based on galaxy gas contents, metallicities and sizes, is found to have a large effect on LBG luminosities. We compare predictions for the size evolution of LBGs at different luminosities with observational data for 2<z<7, and find the Baugh et al. model to be in good agreement. We present predictions for stellar, halo and gas masses, star formation rates, circular velocities, bulge-to-disk ratios, gas and stellar metallicities and clustering bias, as functions of far-UV luminosity and redshift. We find broad consistency with current observational constraints. We then present predictions for the abundance and angular sizes of LBGs out to very high redshift (z<20), finding that planned deep surveys with JWST should detect objects out to z<15. The typical UV luminosities of galaxies are predicted to be very low at high redshifts, which has implications for detecting the galaxies responsible for reionizing the IGM; for example, at z=10, 50% of the ionizing photons are expected to be produced by galaxies fainter than M_AB(1500A)-5logh ~ -15.
Interpreting observations of the Lyman-$α$ forest flux power spectrum requires interpolation between a small number of expensive simulations. We present a Gaussian process emulator modelling the 1D flux power spectrum as a function of the amplitude and slope of the small-scale linear matter power spectrum, and the state of the intergalactic medium at the epoch of interest ($2 < z < 4$). This parameterisation enables the prediction of the flux power spectrum in extended cosmological models that are not explicitly included in the training set, eliminating the need to construct bespoke emulators …
Using cosmological particle hydrodynamical simulations and uniform ultraviolet backgrounds, we compare Lyman-$α$ forest flux spectra predicted by the conventional cold dark matter (CDM) model, the free-particle wave dark matter (FP$ψ$DM) model and extreme-axion wave dark matter (EA$ψ$DM) models of different initial axion field angles against the BOSS Lyman-$α$ forest absorption spectra with a fixed boson mass $m_b\sim 10^{-22}$eV. We recover results reported previously (Iršič et al. 2017b; Armengaud et al. 2017) that the CDM model agrees better with the BOSS data than the FP$ψ$DM model by a la…
A 2.5-3 sigma discrepancy has been reported between the baryonic acoustic oscillation peak (BAO) in the Lyman $α$ forest at $z\sim 2.34$ and the best fit Planck $Λ$CDM cosmology. To isolate the origin of the tension, we consider unanchored BAO, in which the standard BAO ruler is not calibrated, eliminating any dependence on cosmology before redshift $z\sim 2.34$. We consider BOSS BAO measurements at $z\sim 0.32$, 0.57 and 2.34, using the full 2-dimensional constraints on the angular and line of sight BAO scale, as well as isotropic BAO measurements by 6dF and SDSS at $z\sim 0.106$ and $z\sim 0…
We perform a series of cosmological hydrodynamic simulations to investigate the effects of non-gravitational dark matter (DM) interactions on the intergalactic medium (IGM). In particular, we use the ETHOS framework (Cyr-Racine et al. 2016; Vogelsberger et al. 2016) to compare statistics of the Lyman-$α$ forest in cold dark matter (CDM) with an alternative model in which the DM couples strongly with a relativistic species in the early universe. These models are characterised by a cutoff in the linear power spectrum, followed by a series of 'dark acoustic oscillations' (DAOs) on sub-dwarf scale…
Lyman-$α$ forest data are known to be a good probe of the small scale matter power. In this paper, we explore the redshift evolution of the observable effective optical depth $τ_{\rm eff} (z)$ from the Lyman-$α$ data as a discriminator between dark matter models that differ from the $Λ$CDM model on small scales. We consider the thermal warm dark matter (WDM) and the ultra-light axion (ULA) models for the following set of parameters: the mass of ULA, $m_a \simeq 10^{-24}\hbox{--}5 \times 10^{-22} \, \rm eV$ and WDM mass, $m_{\rm wdm} = 0.1 \hbox{--} 4.6 \, \rm keV$. We simulate the line-of-sigh…
Large surveys for Lyman-alpha emitting (LAE) galaxies have been proposed as a new method for measuring clustering of the galaxy population at high redshift with the goal of determining cosmological parameters. However, Lyman-alpha radiative transfer effects may modify the observed clustering of LAE galaxies in a way that mimics gravitational effects, potentially reducing the precision of cosmological constraints. For example, the effect of the linear redshift-space distortion on the power spectrum of LAE galaxies is potentially degenerate with Lyman-alpha radiative transfer effects owing to th…
We show that populations of high redshift galaxies grow more luminous as they grow in linear size. This is because the brightness per unit area has a distinct upper limit due to the self-regulating nature of star-formation. As a corollary, we show that the observed increase in characteristic luminosity of Lyman Break Galaxies (L*) with time can be explained by their increase in size, which scales as 1/H(z). In contrast, Lyman-alpha selected galaxies have a characteristic, constant, small size between redshift z=2.25 and 6.5. Coupled with a characteristic surface brightness, this can explain th…
We present theoretical results for the expected fraction of Lyman Break Galaxies (LBGs) to be detected as strong Lyman alpha emitters (LAEs) in the redshift range 5 < z < 7. We base our analysis on the 2-billion particle SPH simulation MareNostrum High-z Universe. We approximate galaxies as static dusty slabs with an additional clumpy dust distribution affecting stellar populations younger than 25 Myr. The model for the Lyman alpha escape fraction is based on the results of our Monte-Carlo radiative transfer code (CLARA) for a slab configuration. We also fix the transmission of Lyman alpha pho…
The Lyman-$α$ forest is a valuable probe of dark matter models featuring a scale-dependent suppression of the power spectrum as compared to $Λ$CDM. In this work, we present a new estimator of the Lyman-$α$ flux power spectrum that does not rely on hydrodynamical simulations. Our framework is characterized by nuisance parameters that encapsulate the complex physics of the intergalactic medium and sensitivity to highly non-linear small-scale modes. After validating the approach based on high-resolution hydrodynamical simulations for $Λ$CDM, we derive conservative constraints on interacting dark …
We present a physically motivated semi-analytic model to understand the clustering of high redshift Lyman Alpha Emitters (LAEs). We show that the model parameters constrained by the observed luminosity functions, can be used to predict large scale bias and angular correlation function of LAEs. These predictions are shown to reproduce the observations remarkably well. We find that average masses of dark matter halos hosting LAEs brighter than threshold narrow band magnitude ~ 25 are ~ 10^11 M_\odot. These are smaller than that of typical Lyman Break Galaxies (LBGs) brighter than similar thresho…
Lyman-break galaxies are now regularly found in the high redshift Universe by searching for the break in the galaxy spectrum caused by the Lyman-limit redshifted into the optical or even near-IR. At lower redshift, this break is covered by the GALEX UV channels and small samples of z ~ 1 LBGs have been presented in the literature. Here we give results from fitting the spectral energy distributions of a small sub-set of low redshift LBGs and demonstrate the advantage of including photometric points derived from HST ACS slitless grism observations. The results show these galaxies to have very yo…
We have carried out 870 micron observations in the J1040.7-1155 field, known to host an overdensity of Lyman break galaxies at z=5.16 +/- 0.05. We do not detect any individual source at the S(870)=3.0 mJy/beam (2 sigma) level. A stack of nine spectroscopically confirmed z>5 galaxies also yields a non-detection, constraining the submillimeter flux from a typical galaxy at this redshift to S(870)<0.85 mJy, which corresponds to a mass limit M(dust)<1.2x10^8 M_sun (2 sigma). This constrains the mass of thermal dust in distant Lyman break galaxies to less than one tenth of their typical stellar mas…
It has recently been shown that galaxy formation models within the LambdaCDM cosmology predict that, compared to the observed population, small galaxies (with stellar masses < 10^{11} M_sun) form too early, are too passive since z ~ 3 and host too old stellar populations at z=0. We then expect an overproduction of small galaxies at z > 4 that should be visible as an excess of faint Lyman-break galaxies. To check whether this excess is present, we use the MORGANA galaxy formation model and GRASIL spectro-photometric + radiative transfer code to generate mock catalogues of deep fields observed w…
We present confusion limited submillimetre (submm) observations with the SCUBA camera on the JCMT of the z=2.83 Lyman-break galaxy (LBG), Westphal-MM8, reaching an 850um sensitivity even greater than that achieved in the SCUBA map of the Hubble Deep Field region. The detection of Westphal-MM8 (S_{850um} = 1.98+-0.48mJy), along with the literature submm detections of lensed LBGs, suggest that the LBG population may contribute significantly to the source counts of submm selected galaxies in the 1-2mJy regime. Additionally, submm-luminous LBGs are a viable progenitor population for the recently d…
As Lyman-alpha photons are scattered by neutral hydrogen, a change with redshift in the Lyman-alpha equivalent width distribution of distant galaxies offers a promising probe of the degree of ionization in the intergalactic medium and hence when cosmic reionization ended. This simple test is complicated by the fact that Lyman-alpha emission can also be affected by the evolving astrophysical details of the host galaxies. In the first paper in this series, we demonstrated both a luminosity and redshift dependent trend in the fraction of Lyman-alpha emitters seen within color-selected Lyman-break…
The Ly-$α$ forest 1D flux power spectrum is a powerful probe of several cosmological parameters. Assuming a $Λ$CDM cosmology including massive neutrinos, we find that the latest SDSS DR14 BOSS and eBOSS Ly-$α$ forest data is in very good agreement with current weak lensing constraints on $(Ω_m, σ_8)$ and has the same small level of tension with Planck. We did not identify a systematic effect in the data analysis that could explain this small tension, but we show that it can be reduced in extended cosmological models where the spectral index is not the same on the very different times and scale…
We present observations of a luminous galaxy at redshift z=6.573 --- the end of the reioinization epoch --- which has been spectroscopically confirmed twice. The first spectroscopic confirmation comes from slitless HST ACS grism spectra from the PEARS survey (Probing Evolution And Reionization Spectroscopically), which show a dramatic continuum break in the spectrum at restframe 1216 A wavelength. The second confirmation is done with Keck + DEIMOS. The continuum is not clearly detected with ground-based spectra, but high wavelength resolution enables the Lyman alpha emission line profile to be…
Lyman-$α$ forest constraints on pure and mixed fuzzy dark matter
National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；School of Astronomy and Space Sciences, University of Chinese Academy of Sciences（中国科学院大学天文与空间科学学院）；Science Center for Chinese Space Station Survey Telescope, National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台中国空间站巡天望远镜科学中心）
(Abridged) We extend our previous studies aimed at modeling Lyman Alpha Emitters (LAEs) to the second population of high redshift sources, Lyman Break Galaxies (LBGs), with the final goal of investigating the physical relationship between them at 6 < z <8. We use a set of large (~10^6 Mpc^3) cosmological SPH simulations that include a detailed treatment of star formation, feedback, metal enrichment and supernova dust production; these same simulations have already been shown to successfully reproduce a large number of observed properties of LAEs (Dayal et al. 2010). We identify LBGs as galaxie…
We present results of a search for bright Lyman break galaxies at 1.5<=z<=2.5 in the GOODS-S field using a NUV-dropout technique in combination with color-selection. We derived a sample of 73 LBG candidates. We compare our selection efficiencies to BM/BX- and BzK methods (techniques solely based on ground-based data sets), and find the NUV data to provide greater efficiency for selecting star-forming galaxies. We estimate LBG candidate ages, masses, star formation rates, and extinction from fitting PEGASE synthesis evolution models. We find about 20% of our LBG candidates are comparable to inf…
Using deep Keck spectroscopy of Lyman break galaxies selected from infrared imaging data taken with WFC3/IR onboard the Hubble Space Telescope, we present new evidence for a reversal in the redshift-dependent fraction of star forming galaxies with detectable Lyman alpha emission in the redshift range 6.3 < z < 8.8. Our earlier surveys with the DEIMOS spectrograph demonstrated a significant increase with redshift in the fraction of line emitting galaxies over the interval 4 < z < 6, particularly for intrinsically faint systems which dominate the luminosity density. Using the longer wavelength s…
Evidence of dynamical dark energy found via the DESI DR2 Lyman$α$ forest
Dipartimento di Fisica “E. Pancini”, Università degli Studi di Napoli “Federico II”（那不勒斯费德里科二世大学物理系）；Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Napoli（意大利国家核物理研究所那不勒斯分部）；Scuola Superiore Meridionale（南方高等学院）；Research Center of Astrophysics and Cosmology, Khazar University（哈扎尔大学天体物理学与宇宙学研究中心）；Department of Physics, Zhejiang Normal University（浙江师范大学物理系）；Pacif Institute of Cosmology and Selfology (PICS)（帕西夫宇宙学与自我学研究所）
Using about 450,000 galaxies in the Deep Lens Survey, we present a detection of the gravitational magnification of z > 4 Lyman Break Galaxies by massive foreground galaxies with 0.4 < z < 1.0, grouped by redshift. The magnification signal is detected at S/N greater than 20, and rigorous checks confirm that it is not contaminated by any galaxy sample overlap in redshift. The inferred galaxy mass profiles are consistent with earlier lensing analyses at lower redshift. We then explore the tomographic lens magnification signal by splitting our foreground galaxy sample into 7 redshift bins. Combini…
We present the results of a photometric and spectroscopic survey of 321 Lyman break galaxies (LBGs) at z ~ 3 to investigate systematically the relationship between Lya emission and stellar populations. Lya equivalent widths (EW) were calculated from rest-frame UV spectroscopy and optical/near-infrared/Spitzer photometry was used in population synthesis modeling to derive the key properties of age, dust extinction, star formation rate (SFR), and stellar mass. We directly compare the stellar populations of LBGs with and without strong Lya emission, where we designate the former group (EW > 20 AA…
We predict Lyman-$α$ (Ly$α$) luminosity functions (LFs) of Ly$α$-selected galaxies (Ly$α$ emitters, or LAEs) at $z=3-6$ using the phenomenological model of Dijkstra & Wyithe (2012). This model combines observed UV-LFs of Lyman-break galaxies (LBGs, or drop out galaxies), with constraints on their distribution of Ly$α$ line strengths as a function of UV-luminosity and redshift. Our analysis shows that while Ly$α$ LFs of LAEs are generally not Schechter functions, these provide a good description over the luminosity range of $\log_{10}( L_α/{\rm erg}\,{\rm s}^{-1})=41-44$. Motivated by this resu…
We present new information on galaxies in the vicinity of luminous radio galaxies and quasars at z=4,5,6. These fields were previously found to contain overdensities of Lyman Break Galaxies (LBGs) or spectroscopic Lyman alpha emitters. We use HST and Spitzer data to infer stellar masses, and contrast our results with large samples of LBGs in more average environments as probed by the Great Observatories Origins Deep Survey (GOODS). The following results were obtained. First, LBGs in both overdense regions and in the field at z=4-5 lie on a very similar sequence in a z'-[3.6] versus [3.6] color…
We present observations of the CO[3-2] emission towards two massive and infrared luminous Lyman Break Galaxies at z = 3.21 and z = 2.92, using the IRAM Plateau de Bure Interferometer, placing first constraints on the molecular gas masses (Mgas) of non-lensed LBGs. Their overall properties are consistent with those of typical (Main-Sequence) galaxies at their redshifts, with specific star formation rates ~1.6 and ~2.2 Gyr^(-1), despite their large infrared luminosities L_IR ~2-3 x 10^12 Lsun derived from Herschel. With one plausible CO detection (spurious detection probability of 10^(-3)) and o…
We use ultra-deep ultraviolet VLT/VIMOS intermediate-band and VLT/FORS1 narrow-band imaging in the GOODS Southern field to derive limits on the distribution of the escape fraction (f_esc) of ionizing radiation for L >~ L*(z=3) Lyman Break Galaxies (LBGs) at redshift 3.4--4.5. Only one LBG, at redshift z=3.795, is detected in its Lyman continuum (LyC; S/N~5.5), the highest redshift galaxy currently known with a direct detection. Its ultraviolet morphology is quite compact (R_eff=0.8, kpc physical). Three out of seven AGN are also detected in their LyC, including one at redshift z=3.951 and z850…
Lyman Break Analogs (LBAs), characterized by high far-UV luminosities and surface brightnesses as detected by GALEX, are intensely star-forming galaxies in the low-redshift universe ($z\sim 0.2$), with star formation rates reaching up to 50 times that of the Milky Way. These objects present metallicities, morphologies and other physical properties similar to higher redshift Lyman Break Galaxies (LBGs), motivating the detailed study of LBAs as local laboratories of this high-redshift galaxy population. We present results from our recent integral-field spectroscopy survey of LBAs with Keck/OSIRI…
We present deep IRAM Plateau de Bure Interferometer (PdBI) observations, searching for CO-emission toward two massive, non-lensed Lyman break galaxies (LBGs) at z=3.216 and 4.058. With one low significance CO detection (3.5 sigma) and one sensitive upper limit, we find that the CO lines are >~ 3-4 times weaker than expected based on the relation between IR and CO luminosities followed by similarly, massive galaxies at z=0-2.5. This is consistent with a scenario in which these galaxies have low metallicity, causing an increased CO-to-H_2 conversion factor, i.e., weaker CO-emission for a given m…
Measuring star formation rates (SFRs) in high-z galaxies with their rest-frame ultraviolet (UV) continuum can be uncertain because of dust obscuration. Prior studies had used the submillimeter emission at 850 um to determine the intrinsic SFRs of rest-frame UV selected galaxies, but the results suffered from the low sensitivity and poor resolution (~15''). Here, we use ultradeep Very Large Array 1.4 GHz images with ~1''-2'' resolutions to measure the intrinsic SFRs. We perform stacking analyses in the radio images centered on ~3500 Lyman break galaxies (LBGs) at z~4 in the Great Observatories …
For the first time, we study the evolution of the stellar mass-size relation for star-forming galaxies from z ~ 4 to z ~ 7 from Hubble-WFC3/IR camera observations of the HUDF and Early Release Science (ERS) field. The sizes are measured by determining the best fit model to galaxy images in the rest-frame 2100 Å\ with the stellar masses estimated from SED fitting to rest-frame optical (from Spitzer/IRAC) and UV fluxes. We show that the stellar mass-size relation of Lyman-break galaxies (LBGs) persists, at least to z ~ 5, and the median size of LBGs at a given stellar mass increases towards lowe…
We present and discuss the mean rest-frame ultraviolet spectrum for a sample of 81 Lyman Break Galaxies (LBGs) selected to be B-band dropouts with a mean redshift of z=3.9 and apparent magnitudes z_AB<26. Most of the individual spectra are drawn from our ongoing survey in the GOODS fields with the Keck DEIMOS spectrograph, and we have augmented our sample with published data taken with FORS2 on the VLT. In general we find similar trends in the spectral diagnostics to those found in the earlier, more extensive survey of LBGs at z=3 undertaken by Shapley et al (2003). Specifically, we find low-i…
We present spectroscopic confirmation of ten highly luminous (L >= 2L*) Lyman alpha emitters in the redshift range 6.01<z<6.49 (nine galaxies and one AGN), initially drawn from a sample of fourteen z_phot >= 6 Lyman break galaxies (LBGs) selected from an area of 0.25 square degrees within the UKIDSS Ultra-deep Survey (UDS). Overall, our high rate of spectroscopic confirmation (>= 71%) and low rate of contamination provides a strong vindication of the photometric redshift analysis used to define the original sample. By considering star-formation rate estimates based on the Ly_alpha and UV conti…
Distinguishing the nature of dark matter by mapping cosmic filaments from Lyman-alpha emission
Beijing Normal University（北京师范大学）；Zhengzhou University（郑州大学）；Chinese Academy of Sciences（中国科学院）；Westlake University（西湖大学）；Anqing Normal University（安庆师范大学）
Utilizing state-of-the-art, adaptive mesh-refinement cosmological hydrodynamic simulations with ultra-high resolution (114h-1pc) and large sample size (>3300 galaxies of stellar mass >10^9Msun), we show how the stellar light of Lyman Break Galaxies at z=2 is distributed between optical/ultra-violet (UV) and far-infrared (FIR) bands. With a single scalar parameter for dust obscuration we can simultaneously reproduce the observed UV luminosity function for the entire range (3-100 Msun/yr) and extant FIR luminosity function at the bright end (>20Msun/yr). We quantify that galaxies more massive or…
We investigate Lemaître-Tolman-Bondi (LTB) models, whose early time evolution and bang time are homogeneous and the distance - redshift relation and local Hubble parameter are inherited from the $Λ$CDM model. We show that the obtained LTB models and the $Λ$CDM model predict different relative local expansion rates and that the Hubble functions of the models diverge increasingly with redshift. The LTB models show tension between low redshift baryon acoustic oscillation and supernova observations and including Lyman-$α$ forest or cosmic microwave background observations only accentuates the bett…
We study reionization in two non-flat $Λ$CDM inflation models that best fit the Planck 2015 cosmic microwave background anisotropy observations, ignoring or in conjunction with baryon acoustic oscillation distance measurements. We implement a principal component analysis (PCA) to estimate the uncertainties in the reionization history from a joint quasar-CMB dataset. A thorough Markov Chain Monte Carlo analysis is done over the parameter space of PCA modes for both non-flat $Λ$CDM inflation models as well as the original Planck 2016 tilted, spatially-flat $Λ$CDM inflation model. Although both f…
We present a sample of 407 z~3 Lyman break galaxies (LBGs) to a limiting isophotal u-band magnitude of 27.6 mag in the Hubble Ultra Deep Field (UDF). The LBGs are selected using a combination of photometric redshifts and the u-band drop-out technique enabled by the introduction of an extremely deep u-band image obtained with the Keck I telescope and the blue channel of the LRIS spectrometer. The Keck u-band image, totaling 9 hours of integration time, has a one sigma depth of 30.7 mag arcsec^-2, making it one of the most sensitive u-band images ever obtained. The u-band image also substantiall…
Young, massive stars dominate the rest-frame ultraviolet spectra of star-forming galaxies. At high redshifts (z>2), these rest-UV features are shifted into the observed-frame optical and a combination of gravitational lensing, deep spectroscopy and spectral stacking analysis allows the stellar population characteristics of these sources to be investigated. We use our stellar population synthesis code BPASS to fit two strong rest-UV spectral features in published Lyman-break galaxy spectra, taking into account the effects of binary evolution on the stellar spectrum. In particular, we consider t…
Lyman Break Galaxies (LBGs) are widely thought to be prototypical young galaxies in the early universe, particularly representative of those undergoing massive events of star formation. Therefore, LBGs should produce significant amounts of X-ray emission. We aim to trace the X-ray luminosity of Lyman Break Galaxies across cosmic time and from that derive constraints on their star formation history. We utilize the newly released 4 Ms mosaic obtained with the Chandra X-ray Observatory, the deepest X-ray image to date, alongside with the superb spectroscopic data sets available in the CDF-S surve…
We investigate the cross-correlation between the spatial distribution of Lyman Break Galaxies (LBGs) and the 21cm intensity mapping signal at $z\sim[3-5]$. At these redshifts, galactic feedback is supposed to only marginally affect the matter power spectrum, and the neutral hydrogen distribution is independently constrained by quasar spectra. Using a high resolution N-body simulation, populated with neutral hydrogen a posteriori, we forecast for the expected LBG-21cm cross-spectrum and its error for a 21cm field observed by the Square Kilometre Array (SKA1-LOW and SKA1-MID), combined with a sp…
We present results of optical spectroscopic observations of candidates of Lyman Break Galaxies (LBGs) at $z \sim 5$ in the region including the GOODS-N and the J0053+1234 region by using GMOS-N and GMOS-S, respectively. Among 25 candidates, five objects are identified to be at $z \sim 5$ (two of them were already identified by an earlier study) and one object very close to the color-selection window turned out to be a foreground galaxy. With this spectroscopically identified sample and those from previous studies, we derived the lower limits on the number density of bright ($M_{UV}<-22.0$ mag)…
