arXiv subjects

Nelson Padilla

Publications and source records attributed to Nelson Padilla.

At least 73 records · Page 4Linked to original sources

arXiv2015

Towards the statistical detection of the warm-hot intergalactic medium in inter-cluster filaments of the cosmic web

Modern analyses of structure formation predict a universe tangled in a 'cosmic web' of dark matter and diffuse baryons. These theories further predict that at low-z, a significant fraction of the baryons will be shock-heated to $T \sim 10^{5}-10^{7}$K yielding a warm-hot intergalactic medium (WHIM), but whose actual existence has eluded a firm observational confirmation. We present a novel experiment to detect the WHIM, by targeting the putative filaments connecting galaxy clusters. We use HST/COS to observe a remarkable QSO sightline that passes within $Δd = 3$ Mpc from the 7 inter-cluster axes connecting 7 independent cluster-pairs at redshifts $0.1 \le z \le 0.5$. We find tentative excesses of total HI, narrow HI (NLA; Doppler parameters $b<50$ km/s), broad HI (BLA; $b \ge 50$ km/s) and OVI absorption lines within rest-frame velocities of $Δv \lesssim 1000$ km/s from the cluster-pairs redshifts, corresponding to $\sim 2$, $\sim 1.7$, $\sim 6$ and $\sim 4$ times their field expectations, respectively. Although the excess of OVI likely comes from gas close to individual galaxies, we conclude that most of the excesses of NLAs and BLAs are truly intergalactic. We find that the covering fractions, $f_c$, of BLAs close to cluster-pairs are $\sim 4-7$ times higher than the random expectation (at the $\sim 2 σ$ c.l.), whereas the $f_c$ of NLAs and OVI are not significantly enhanced. We argue that a larger relative excess of BLAs compared to those of NLAs close to cluster-pairs may be a signature of the WHIM in inter-cluster filaments. By extending the present analysis to tens of sightlines our experiment offers a promising route to detect the WHIM.

astro-ph.CO↗

arXiv2015

The nebular emission of star-forming galaxies in a hierarchical universe

Galaxy surveys targeting emission lines are characterising the evolution of star-forming galaxies, but there is still little theoretical progress in modelling their physical properties. We predict nebular emission from star-forming galaxies within a cosmological galaxy formation model. Emission lines are computed by combining the semi-analytical model \sag\ with the photoionisation code \mapp. We characterise the interstellar medium (ISM) of galaxies by relating the ionisation parameter of gas in galaxies to their cold gas metallicity, obtaining a reasonable agreement with the observed \ha, \oii, \oiii\ luminosity functions, and the the BPT diagram for local star-forming galaxies. The average ionisation parameter is found to increase towards low star-formation rates and high redshifts, consistent with recent observational results. The predicted link between different emission lines and their associated star-formation rates is studied by presenting scaling relations to relate them. Our model predicts that emission line galaxies have modest clustering bias, and thus reside in dark matter haloes of masses below $M_{\rm halo} \lesssim 10^{12} {[\rm h^{-1} M_{\odot}]}$. Finally, we exploit our modelling technique to predict galaxy number counts up to $z\sim 10$ by targeting far-infrared (FIR) emission lines detectable with submillimetre facilities

astro-ph.CO↗

arXiv2014

Testing Gravity using Void Profiles

We investigate void properties in $f(R)$ models using N-body simulations, focusing on their differences from General Relativity (GR) and their detectability. In the Hu-Sawicki $f(R)$ modified gravity (MG) models, the halo number density profiles of voids are not distinguishable from GR. In contrast, the same $f(R)$ voids are more empty of dark matter, and their profiles are steeper. This can in principle be observed by weak gravitational lensing of voids, for which the combination of a spectroscopic redshift and a lensing photometric redshift survey over the same sky is required. Neglecting the lensing shape noise, the $f(R)$ model parameter amplitudes $|f_{R0}|=10^{-5}$ and $10^{-4}$ may be distinguished from GR using the lensing tangential shear signal around voids by 4 and 8$σ$ for a volume of 1~(Gpc/$h$)$^3$. The line-of-sight projection of large-scale structure is the main systematics that limits the significance of this signal for the near future wide angle and deep lensing surveys. For this reason, it is challenging to distinguish $|f_{R0}|=10^{-6}$ from GR. We expect that this can be overcome with larger volume. The halo void abundance being smaller and the steepening of dark matter void profiles in $f(R)$ models are unique features that can be combined to break the degeneracy between $|f_{R0}|$ and $σ_8$.

astro-ph.CO↗

arXiv2014

Testing Gravity using Cosmic Voids

We explore voids in dark matter and halo fields from simulations of $Λ$CDM and Hu-Sawicki $f(R)$ models. In $f(R)$ gravity, dark matter void abundances are greater than that of general relativity (GR). However, when using haloes to identify voids, the differences of void abundances become much smaller, but can still be told apart, in principle, at the 2, 6 and 14 $σ$ level for the $f(R)$ model parameter amplitudes of $|f_{R0}|=10^{-6}$, $10^{-5}$ and $10^{-4}$. In contrast, the abundance of large voids found using haloes in $f(R)$ gravity is lower than in GR. The more efficient halo formation in underdense regions makes $f(R)$ voids less empty of haloes. This counter intuitive result suggests that voids are not necessarily emptier in $f(R)$ if one looks at galaxies in voids. Indeed, the halo number density profiles of voids are not distinguishable from GR. However, the same $f(R)$ voids are more empty of dark matter. This can in principle be observed by weak gravitational lensing of voids, for which the combination of a spec-$z$ and a photo-$z$ survey over the same sky is necessary. For a volume of 1~(Gpc/$h$)$^3$, neglecting the lensing shape noise, $|f_{R0}|=10^{-5}$ and $10^{-4}$ may be distinguished from GR using the lensing tangential shear signal around voids by 4 and 8$σ$. The line-of-sight projection of large-scale structure is the main systematics that limits the significance of this signal, limiting the constraining power for $|f_{R0}|=10^{-6}$. The halo void abundance being smaller and the steepening of dark matter void profiles in $f(R)$ models are unique features that can be combined to break the degeneracy between $|f_{R0}|$ and $σ_8$. The outflow of mass from void centers and velocity dispersions are greater in $f(R)$. Model differences in velocity profiles imply potential powerful constraints of the model in phase space and in redshift space.

astro-ph.CO↗

arXiv2014

Void Dynamics

Cosmic voids are becoming key players in testing the physics of our Universe. Here we concentrate on the abundances and the dynamics of voids as these are among the best candidates to provide information on cosmological parameters. Cai, Padilla \& Li (2014) use the abundance of voids to tell apart Hu \& Sawicki $f(R)$ models from General Relativity. An interesting result is that even though, as expected, voids in the dark matter field are emptier in $f(R)$ gravity due to the fifth force expelling away from the void centres, this result is reversed when haloes are used to find voids. The abundance of voids in this case becomes even lower in $f(R)$ compared to GR for large voids. Still, the differences are significant and this provides a way to tell apart these models. The velocity field differences between $f(R)$ and GR, on the other hand, are the same for halo voids and for dark matter voids. Paz et al. (2013), concentrate on the velocity profiles around voids. First they show the necessity of four parameters to describe the density profiles around voids given two distinct void populations, voids-in-voids and voids-in-clouds. This profile is used to predict peculiar velocities around voids, and the combination of the latter with void density profiles allows the construction of model void-galaxy cross-correlation functions with redshift space distortions. When these models are tuned to fit the measured correlation functions for voids and galaxies in the Sloan Digital Sky Survey, small voids are found to be of the void-in-cloud type, whereas larger ones are consistent with being void-in-void. This is a novel result that is obtained directly from redshift space data around voids. These profiles can be used to remove systematics on void-galaxy Alcock-Pacinsky tests coming from redshift-space distortions.

astro-ph.CO↗

arXiv2014

Stochastic angular momentum slews and flips and their effect on discs in galaxy formation models

The angular momentum of galactic discs in semi-analytic models of galaxy formation is usually updated in time as material is accreted to the disc by adopting a constant dimensionless spin parameter and little attention is paid to the effects of accretion with misaligned angular momenta. These effects are the subject of this paper, where we adopt a Monte-Carlo simulation for the changes in the direction of the angular momentum of a galaxy disc as it accretes matter based on accurate measurements from dark-matter haloes in the Millennium II simulation. In our semi-analytic model implementation, the flips seen the dark matter haloes are assumed to be the same for the cold baryons; however, we also assume that in the latter the flip also entails a difficulty for the disc to increase its angular momentum which causes the disc to become smaller relative to a no-flip case. This makes star formation to occur faster, specially in low mass galaxies at all redshifts allowing galaxies to reach higher stellar masses faster. We adopt a new condition for the triggering of starbursts during mergers. As these produce the largest flips it is natural to adopt the disc instability criterion to evaluate the triggering of bursts in mergers instead of one based on mass ratios as in the original model. The new implementation reduces the average lifetimes of discs by a factor of 2, while still allowing old ages for the present-day discs of large spiral galaxies. It also provides a faster decline of star formation in massive galaxies and a better fit to the bright end of the luminosity function at z = 0.

astro-ph.GA↗

arXiv2014

The nature of assembly bias - III. Observational properties

We analyse galaxies in groups in the Sloan Digital Sky Survey (SDSS) and find a weak but significant assembly-type bias, where old central galaxies have a higher clustering amplitude (61 $\pm$ 9 per cent) at scales > 1 Mpc than young central galaxies of equal host halo mass ($M_{h} \sim 10^{11.8} h^{-1}$ $M_{\odot}$). The observational sample is volume-limited out to z=0.1 with $M_r -$ 5 log$(h) \le -19.6$. We construct a mock catalogue of galaxies that shows a similar signal of assembly bias (46 $\pm$ 9 per cent) at the same halo mass. We then adapt the model presented by Lacerna & Padilla (Paper I) to redefine the overdensity peak height, which traces the assembly bias such that galaxies in equal density peaks show the same clustering regardless of their stellar age, but this time using observational features such as a flux limit. The proxy for peak height, which is proposed as a better alternative than the virial mass, consists in the total mass given by the mass of neighbour host haloes in cylinders centred at each central galaxy. The radius of the cylinder is parametrized as a function of stellar age and virial mass. The best-fitting set of parameters that make the assembly bias signal lower than 5$-$15 per cent for both SDSS and mock central galaxies are similar. The idea behind the parametrization is not to minimize the bias, but it is to use this method to understand the physical features that produce the assembly bias effect. Even though the tracers of the density field used here differ significantly from those used in paper I, our analysis of the simulated catalogue indicates that the different tracers produce correlated proxies, and therefore the reason behind this assembly bias is the crowding of peaks in both simulations and the SDSS.

astro-ph.CO↗

arXiv2014

Cosmic web alignments with the shape, angular momentum and peculiar velocities of dark matter haloes

We study the alignment of dark matter haloes with the cosmic web characterized by the tidal and velocity shear fields. We focus on the alignment of their shape, angular momentum and peculiar velocities. We use a cosmological N-body simulation that allows to study dark matter halos spanning almost five orders of magnitude in mass ($10^{9}$-$10^{14}$) $h^{-1}$$M_{\odot}$ and spatial scales of $(0.5$-$1.0)$ $h^{-1}$ Mpc to define the cosmic web. We find that the halo shape presents the strongest alignment along the smallest tidal eigenvector, e.g. along filaments and walls, with a signal that gets stronger as the halo mass increases. In the case of the velocity shear field only massive halos $>10^{12}$ $h^{-1}$$M_{\odot}$ tend to have their shapes aligned along the largest tidal eigenvector; that is, perpendicular to filaments and walls. For the angular momentum we find alignment signals only for halos more massive than $10^{12}$ $h^{-1}$$M_{\odot}$ both in the tidal and velocity shear webs where the preferences are for it to be parallel to the middle eigenvector; perpendicular to filaments and parallel to walls. Finally, the peculiar velocities show a strong alignment along the smallest tidal eigenvector for all halo masses; halos move along filaments and walls. In the velocity shear the same alignment is present but weaker and only for haloes less massive than $10^{12}$ $h^{-1}$$M_{\odot}$. Our results clearly show that the two different algorithms we used to define the cosmic web describe different physical aspects of non-linear collapse and should be used in a complementary way to understand the effect of the cosmic web on galaxy evolution.

astro-ph.CO↗

arXiv2014

VISTA Variables in the Vía Láctea (VVV): Halfway Status and Results

The VISTA Variables in the Vía Láctea (VVV) survey is one of six public ESO surveys, and is now in its 4th year of observing. Although far from being complete, the VVV survey has already delivered many results, some directly connected to the intended science goals (detection of variables stars, microlensing events, new star clusters), others concerning more exotic objects, e.g. novae. Now, at the end of the fourth observing period, and comprising roughly 50% of the proposed observations, the actual status of the survey, as well some of the results based on the VVV data, are presented.

astro-ph.IM↗

arXiv2014

Kinematic analysis of a sample of X-ray luminous distant galaxy clusters. The $L_X$ - $σ_v$ relation in the $z>0.6$ universe

Observations and cosmological simulations show galaxy clusters as a family of nearly self-similar objects with properties that can be described by scaling relations as a function of e.g. mass and time. Here we study the scaling relations between the galaxy velocity dispersion and X-ray quantities like X-ray bolometric luminosity and temperature in galaxy clusters at high redshifts (0.64 $\leq$ z $\leq$ 1.46). We also compare our results with the similar study of the local HIFLUGCS sample. For the analysis, we use a set of 15 distant galaxy clusters extracted from the literature plus a sample of 10 newly discovered clusters selected in X-rays by the \XMM Distant Cluster Project (XDCP) with more than 10 confirmed spectroscopic members per cluster. We also study the evolution of this scaling relation by comparing the high redshift results with the data from the local HIFLUGCS sample. We also investigated the $L_X - T_X$ and the $σ_v - T_X$ relations for the 15 clusters in the literature sample. We report the results of the X-ray and kinematic analysis of 10 newly detected high redshift clusters and provide their spectroscopic and kinematic details. For the entire, distant sample we find a slope fully consistent with the one typical of local clusters, albeit with a large associated uncertainty. The study on the evolution of the amplitude reveals a positive offset if the self-similar evolution is neglected, hence possibly indicating the need for including evolutionary effects. However, the $L_X - T_X$ relation is found to be in good agreement with the local relation without any significant redshift evolution. Finally, the $σ_v - T_X$ relation appears to slightly deviate from the theoretical expectation that galaxies and gas particles have a similar specific kinetic energy. However, the associated uncertainty is currently too large for making any conclusive statement in this regard.

astro-ph.CO↗

arXiv2013

To Stack or Not to Stack: Spectral Energy Distribution Properties of Lya-Emitting Galaxies at z=2.1

We use the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (CANDELS) GOODS-S multi-wavelength catalog to identify counterparts for 20 Lya Emitting (LAE) galaxies at z=2.1. We build several types of stacked Spectral Energy Distributions (SEDs) of these objects. We combine photometry to form average and median flux-stacked SEDs, and postage stamp images to form average and median image-stacked SEDs. We also introduce scaled flux stacks that eliminate the influence of variation in overall brightness. We use the SED fitting code SpeedyMC to constrain the physical properties of individual objects and stacks. Our LAEs at z = 2.1 have stellar masses ranging from 2x10^7 Msun - 8x10^9 Msun (median = 3x10^8 Msun), ages ranging from 4 Myr to 500 Myr (median =100 Myr), and E(B-V) between 0.02 and 0.24 (median = 0.12). We do not observe strong correlations between Lya equivalent width (EW) and stellar mass, age, or E(B-V). The Lya radiative transfer (q) factors of our sample are predominantly close to one and do not correlate strongly with EW or E(B-V), implying that Lya radiative transfer prevents Lya photons from resonantly scattering in dusty regions. The SED parameters of the flux stacks match the average and median values of the individual objects, with the flux-scaled median SED performing best with reduced uncertainties. Median image-stacked SEDs provide a poor representation of the median individual object, and none of the stacking methods captures the large dispersion of LAE properties.

astro-ph.CO↗

arXiv2013

Clues on void evolution II: Measuring density and velocity profiles on SDSS galaxy redshift space distortions

Using the redshift-space distortions of void-galaxy cross-correlation function we analyse the dynamics of voids embedded in different environments. We compute the void-galaxy cross-correlation function in the Sloan Digital Sky Survey (SDSS) in terms of distances taken along the line of sight and projected into the sky. We analyse the distortions on the cross-correlation isodensity levels and we find anisotropic isocontours consistent with expansion for large voids with smoothly rising density profiles and collapse for small voids with overdense shells surrounding them. Based on the linear approach of gravitational collapse theory we developed a parametric model of the void-galaxy redshift space cross-correlation function. We show that this model can be used to successfully recover the underlying velocity and density profiles of voids from redshift space samples. By applying this technique to real data, we confirm the twofold nature of void dynamics: large voids typically are in an expansion phase whereas small voids tend to be surrounded by overdense and collapsing regions. These results are obtained from the SDSS spectroscopic galaxy catalogue and also from semi-analytic mock galaxy catalogues, thus supporting the viability of the standard LCDM model to reproduce large scale structure and dynamics.

astro-ph.CO↗

arXiv2013

Magellan/MMIRS near-infrared multi-object spectroscopy of nebular emission from star forming galaxies at 2<z<3

To investigate the ingredients, which allow star-forming galaxies to present Lyalpha line in emission, we studied the kinematics and gas phase metallicity (Z) of the interstellar medium. We used multi-object NIR spectroscopy with Magellan/MMIRS to study nebular emission from z=2-3 star-forming galaxies discovered in 3 MUSYC fields. We detected emission lines from four active galactic nuclei and 13 high-z star-forming galaxies, including Halpha lines down to a flux of 4.E-17 erg/sec/cm^2. This yielded 7 new redshifts. The most common emission line detected is [OIII]5007, which is sensitive to Z. We were able to measure Z for 2 galaxies and to set upper(lower) limits for another 2(2). The Z values are consistent with 0.3<Z/Zsun<1.2. Comparing the Lyalpha central wavelength with the systemic redshift, we find Delta_v(Lyalpha-[OIII])=70-270 km/sec. High-redshift star-forming galaxies, Lyalpha emitting (LAE) galaxies, and Halpha emitters appear to be located in the low mass, high star-formation rate (SFR) region of the SFR versus stellar mass diagram, confirming that they are experiencing burst episodes of star formation, which are building up their stellar mass. Their Zs are consistent with the relation found for z<2.2 galaxies in the Z versus stellar mass plane. The measured Delta_v(Lyalpha-[OIII]) values imply that outflows of material, driven by star formation, could be present in the z=2-3 LAEs of our sample. Comparing with the literature, we note that galaxies with lower Z than ours are also characterized by similar Delta_v(Lyalpha-[OIII]) velocity offsets. Strong [OIII] is detected in many Lyalpha emitters. Therefore, we propose the Lyalpha/[OIII] flux ratio as a tool for the study of high-z galaxies; while influenced by Z, ionization, and Lyalpha radiative transfer in the ISM, it may be possible to calibrate this ratio to primarily trace one of these effects.

astro-ph.CO↗

arXiv2013

How robust are predictions of galaxy clustering?

We use the Millennium Simulation database to compare how different versions of the Durham and Munich semi-analytical galaxy formation models populate dark matter haloes with galaxies. The models follow the same physical processes but differ in how these are implemented. All of the models we consider use the Millennium N-body Simulation; however, the Durham and Munich groups use independent algorithms to construct halo merger histories. We compare the predicted halo occupation distributions (HODs) and correlation functions for galaxy samples defined by stellar mass, cold gas mass and star formation rate. The predictions for the HOD are remarkably similar for samples ranked by stellar mass. The predicted bias averaged over 5-25 Mpc/h is consistent between models to within 10%. At small pair separations there is a difference in the predicted clustering. This arises because the Durham models allow some satellite galaxies to merge with the central galaxy in a halo when they are still associated with resolved subhaloes. The agreement between the models is less good for samples defined by cold gas mass or star formation rate, with the small scale clustering differing by an order of magnitude, reflecting the uncertainty in the modelling of star formation. The model predictions in these cases are qualitatively similar, with a markedly shallower slope for the correlation function than is found for stellar mass selected samples and with the HOD displaying an asymmetric peak for central galaxies. We provide illustrative parametric fits to the HODs predicted by the models. Our results reveal the current limitations on how well we can predict galaxy bias in a fixed cosmology, which has implications for the interpretation of constraints on the physics of galaxy formation from galaxy clustering measurements and the ability of future galaxy surveys to measure dark energy.

astro-ph.CO↗

arXiv2012

The influence of superstructures on bright galaxy environments: clustering properties

We analyse the dependence of clustering properties of galaxies as a function of their large-scale environment. In order to characterize the environment on large scales, we use the catalogue of future virialized superstructures (FVS) by Luparello et al. and separate samples of luminous galaxies according to whether or not they belong to FVS. In order to avoid biases in the selection of galaxies, we have constructed different subsamples so that the distributions of luminosities and masses are comparable outside and within FVS. As expected, at large scales, there is a strong difference between the clustering of galaxies inside and outside FVS. However, this behaviour changes at scales r < 1 Mpc/h, where the correlations have similar amplitudes. The amplitude of the two-halo term of the correlation function for objects inside FVS does not depend on their mass, but rather on that of the FVS. This is confirmed by comparing this amplitude with that expected from extended Press-Schechter fits. In order to compare these observational results with current models for structure formation, we have performed a similar analysis using a semi-analytic implementation in a LCDM cosmological model. We find that the cross-correlation functions from the mock catalogue depend on the large-scale structures in a similar way to the observations. From our analysis, we conclude that the clustering of galaxies within the typical virialized regions of groups, mainly depends on the halo mass, irrespective of the large-scale environment.

astro-ph.CO↗

arXiv2012

The nature of assembly bias - II. Halo spin

We study an assembly-type bias parametrized by the dimensionless spin parameter that affects massive structures. In numerical simulations higher spin haloes are more strongly clustered than lower spin haloes of equal mass. We detect a difference of over a 30 per cent in the clustering strength for dark matter haloes of 10^13-10^14 Msun, which is similar to the result of Bett et al. We explore whether the dependence of clustering strength on halo spin is removed if we apply the redefinition of overdensity peak height proposed by Lacerna & Padilla (Paper I) obtained using assembly ages. We find that this is not the case due to two reasons. Firstly, only a few objects of low-virial mass are moved into the mass range where the spin introduces an assembly bias after using this redefinition. Secondly, this formalism does not alter the mass of massive objects. We then repeat the process of finding the redefined peak height of Paper I but using the spin. In this case, the new masses show no spin-related assembly bias but they introduce a previously absent assembly bias with respect to relative age. From this result, we conclude that the assembly-type bias with respect to the halo spin has a different origin than with respect to assembly age. The former may be due to the material from filaments, which is accreted by massive haloes, that is enhanced in high-density environments, thus causing more extreme spin values without significantly changing the formation age of the halo. In addition, high-mass objects may correspond, in some cases, to a different peak height than that suggested by their mass in numerical simulations, providing a possible explanation for the assembly bias with respect to spin. (abridged)

astro-ph.CO↗

arXiv2012

Present-Day Descendants of z=3 Ly-α Emitting Galaxies in the Millennium-II Halo Merger Trees

Using the Millennium-II Simulation dark matter sub-halo merger histories, we created mock catalogs of Lyman Alpha Emitting (LAE) galaxies at z=3.1 to study the properties of their descendants. Several models were created by selecting the sub-halos to match the number density and typical dark matter mass determined from observations of these galaxies. We used mass-based and age-based selection criteria to study their effects on descendant populations at z~2, 1 and 0. For the models that best represent LAEs at z=3.1, the z=0 descendants have a median dark matter halo mass of 10^12.7 M_Sun, with a wide scatter in masses (50% between 10^11.8 and 10^13.7 M_Sun). Our study differentiated between central and satellite sub-halos and found that ~55% of z=0 descendants are central sub-halos with M_Median~10^12 M_Sun. This confirms that central z=0 descendants of z=3.1 LAEs have halo masses typical of L* type galaxies. The satellite sub-halos reside in group/cluster environments with dark matter masses around 10^14 M_Sun. The median descendant mass is robust to various methods of age determination, but it could vary by a factor of 5 due to current observational uncertainties in the clustering of LAEs used to determine their typical z=3.1 dark matter mass.

astro-ph.CO↗

arXiv2012

Stacked Rest-Frame UV Spectra of Ly$α$-Emitting and Continuum-Selected Galaxies at 2<z<3.5

We present properties of individual and composite rest-UV spectra of continuum- and narrowband-selected star-forming galaxies (SFGs) at a redshift of 2 20 Å, the canonical limit to be classified as a LAE. We divide our dataset into subsamples based on properties we are able to measure for each individual galaxy: Lyα equivalent width, rest-frame UV colors, and redshift. Among our subsample of galaxies with R<25.5, those with rest-frame W_{Lyα}>20 Å have bluer UV continua, weaker low-ionization interstellar absorption lines, weaker C IV absorption, and stronger Si II* nebular emission than those with W_{Lyα}<20 Å. We measure a typical velocity offset of Δv~600 km s$^{-1}$ between Lyα emission and low-ionization absorption among our subsamples. We find that the interstellar component, as opposed to the stellar component, dominates the high-ionization absorption line profiles. We find the low- and high-ionization Si ionization states have similar kinematic properties, yet the low-ionization absorption is correlated with Ly$α$ emission and the high-ionization absorption is not. These trends are consistent with outflowing neutral gas being in the form of neutral clouds embedded in ionized gas as previously suggested by \cite{Steidel2010}. Moreover, our galaxies with bluer UV colors have stronger Lyα emission, weaker low-ionization absorption and more prominent nebular emission line profiles. Among our dataset, UV-bright galaxies with W_{Lyα}>20 Å exhibit weaker Lyα emission at lower redshifts, although we caution that this could be caused by spectroscopic confirmation of low Lyα equivalent width galaxies being harder at z~3 than z~2.

astro-ph.CO↗