- ID:
- ivo://CDS.VizieR/J/MNRAS/442/3565
- Title:
- L-{sigma} relation for massive star formation
- Short Name:
- J/MNRAS/442/3565
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The validity of the emission-line luminosity versus ionized gas velocity dispersion (L-{sigma}) correlation for HII galaxies (HIIGx) and its potential as an accurate distance estimator are assessed. For a sample of 128 local (0.02<~z<~0.2) compact HIIGx with high equivalent widths of their Balmer emission lines, we obtained the ionized gas velocity dispersion from high signal-to-noise ratio (S/N) high-dispersion spectroscopy (Subaru High Dispersion Spectrograph (HDS) and European Southern Observatory (ESO) Very Large Telescope Ultraviolet and Visual Echelle Spectrograph (VLT-UVES)) and integrated H{beta} fluxes from low-dispersion wide aperture spectrophotometry. We find that the L(H{beta})-{sigma} relation is strong and stable against restrictions in the sample (mostly based on the emission-line profiles). The `Gaussianity' of the profile is important for reducing the root-mean-square (rms) uncertainty of the distance indicator, but at the expense of substantially reducing the sample. By fitting other physical parameters into the correlation, we are able to decrease the scatter significantly without reducing the sample. The size of the star-forming region is an important second parameter, while adding the emission-line equivalent width or the continuum colour and metallicity produces the solution with the smallest rms scatter={delta}logL(H{beta})=0.233. The derived coefficients in the best L(H{beta})-{sigma} relation are very close to what is expected from virialized ionizing clusters, while the derived sum of the stellar and ionized gas masses is similar to the dynamical mass estimated using the Hubble Space Telescope} (HST}) corrected Petrosian radius. These results are compatible with gravity being the main mechanism causing the broadening of the emission lines in these very young and massive clusters. The derived masses range from about 2x10^6^M_{sun}_ to 10^9^M_{sun}_ and their 'corrected' Petrosian radius ranges from a few tens to a few hundred pc.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/617/A130
- Title:
- Luminous infrared galaxies AKARI 2.5-5um data
- Short Name:
- J/A+A/617/A130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present AKARI 2.5-5um spectra of 145 local luminous infrared galaxies (LIRG; L_IR_>=10^11^L_{sun}_) in the Great Observatories All-sky LIRG Survey (GOALS). In all of the spectra, we measure the line fluxes and equivalent widths (EQWs) of the polycyclic aromatic hydrocarbon (PAH) at 3.3um and the hydrogen recombination line Br{alpha} at 4.05um, with apertures matched to the slit sizes of the Spitzer low-resolution spectrograph and with an aperture covering ~95% of the total flux in the AKARI two-dimensional (2D) spectra. The star formation rates (SFRs) derived from the Br{alpha} emission measured in the latter aperture agree well with SFRs estimated from LIR, when the dust extinction correction is adopted based on the 9.7um silicate absorption feature. Together with the Spitzer Infrared Spectrograph (IRS) 5.2-38um spectra, we are able to compare the emission of the PAH features detected at 3.3um and 6.2um. These are the two most commonly used near/mid-infrared indicators of starburst or active galactic nucleus (AGN) dominated galaxies. We find that the 3.3um and 6.2um PAH EQWs do not follow a linear correlation and at least a third of the galaxies classified as AGN-dominated sources using the 3.3um feature are classified as starbursts based on the 6.2um feature. These galaxies have a bluer continuum slope than galaxies that are indicated to be starburst-dominated by both PAH features. The bluer continuum emission suggests that their continuum is dominated by stellar emission rather than hot dust. We also find that the median Spitzer/IRS spectra of these sources are remarkably similar to the pure starburst-dominated sources indicated by high PAH EQWs in both 3.3um and 6.2um. Based on these results, we propose a revised starburst/AGN diagnostic diagram using 2-5um data: the 3.3um PAH EQW and the continuum color, F{nu}(4.3um)/F{nu}(2.8um). We use the AKARI and Spitzer spectra to examine the performance of our new starburst/AGN diagnostics and to estimate 3.3um PAH fluxes using the James Webb Space Telescope (JWST) photometric bands in the redshift range 0<z<5. Of the known PAH features and mid-infrared high ionization emission lines used as starburst/AGN indicators, only the 3.3um PAH feature is observable with JWST at z>3.5, because the rest of the features at longer wavelengths fall outside the JWST wavelength coverage.
- ID:
- ivo://CDS.VizieR/J/MNRAS/477/2817
- Title:
- Luminous Ly{alpha} emitters at z~2-3
- Short Name:
- J/MNRAS/477/2817
- Date:
- 02 Mar 2022 00:40:05
- Publisher:
- CDS
- Description:
- Deep narrow-band surveys have revealed a large population of faint Ly{alpha} emitters (LAEs) in the distant Universe, but relatively little is known about the most luminous sources (L_Lya_>~10^42.7^erg/s; L_Lya>~L^*^_Lya_). Here we present the spectroscopic follow-up of 21 luminous LAEs at z~2-3 found with panoramic narrow-band surveys over five independent extragalactic fields (=~4x10^6^Mpc^3^ surveyed at z~2.2 and z~3.1). We use WHT/ISIS, Keck/DEIMOS, and VLT/X-SHOOTER to study these sources using high ionization UV lines. Luminous LAEs at z~2-3 have blue UV slopes ({beta}=-2.0^+0.3^_-0.1_) and high Ly{alpha} escape fractions (50^+20^_-15_ per cent) and span five orders of magnitude in UV luminosity (M_UV_=~-19 to -24). Many (70 per cent) show at least one high ionization rest-frame UV line such as CIV, NV, CIII], HeII or OIII], typically blue-shifted by =~100-200km/s relative to Ly{alpha}. Their Ly{alpha} profiles reveal a wide variety of shapes, including significant blue-shifted components and widths from 200 to 4000km/s. Overall, 60+/-11 per cent appear to be active galactic nucleus (AGN) dominated, and at L_Lya_>10^43.3^erg/s and/or M_UV_<-21.5 virtually all LAEs are AGNs with high ionization parameters (logU=0.6+/-0.5) and with metallicities of =~0.5-1Z_{sun}_. Those lacking signatures of AGNs (40+/-11 per cent) have lower ionization parameters (logU=-3.0^+1.6^_-0.9_ and log{xi}_ion_=25.4+/-0.2) and are apparently metal-poor sources likely powered by young, dust-poor 'maximal' starbursts. Our results show that luminous LAEs at z~2-3 are a diverse population and that 2xL^*^_Lya_ and 2*M_UV_^*^ mark a sharp transition in the nature of LAEs, from star formation dominated to AGN dominated.
- ID:
- ivo://CDS.VizieR/J/ApJ/888/89
- Title:
- Lya galaxies in 3 CFHTLS overdense regions
- Short Name:
- J/ApJ/888/89
- Date:
- 25 Oct 2021 10:16:31
- Publisher:
- CDS
- Description:
- We have carried out follow-up spectroscopy on three overdense regions of g- and r-dropout galaxies in the Canada-France-Hawaii Telescope Legacy Survey Deep Fields, finding two new protoclusters at z=4.898 and 3.721 and a possible protocluster at z=3.834. The z=3.721 protocluster overlaps with a previously identified protocluster at z=3.675. The redshift separation between these two protoclusters is {Delta}z=0.05, which is slightly larger than the size of typical protoclusters. Therefore, if they are not the progenitors of a >10^15^M_{sun}_ halo, they would grow into closely located independent halos like a supercluster. The other protocluster at z=4.898 is also surrounded by smaller galaxy groups. These systems including protoclusters and neighboring groups are regarded as the early phase of superclusters. We quantify the spatial distribution of member galaxies of the protoclusters at z=3.675 and 3.721 by fitting triaxial ellipsoids, finding a tentative difference: one has a pancake-like shape, while the other is filamentary. This could indicate that these two protoclusters are in different stages of formation. We investigate the relation between redshift and the velocity dispersion of protoclusters, including other protoclusters from the literature, in order to compare their dynamical states. Although there is no significant systematic trend in the velocity dispersions of protoclusters with redshift, the distribution is skewed to higher velocity dispersion over the redshift range of z=2-6. This could be interpreted as two phases of cluster formation, one dominated by the steady accretion of galaxies and the other by the merging between group-size halos, perhaps depending on the surrounding large-scale environments.
- ID:
- ivo://CDS.VizieR/J/ApJ/559/654
- Title:
- Ly{alpha} absorption systems. V.
- Short Name:
- J/ApJ/559/654
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a program to obtain and analyze HST WFPC2 images and ground-based images of galaxies identified in an imaging and spectroscopic survey of faint galaxies in fields of HST spectroscopic target QSOs. Here we present the additional HST WFPC2 observations of galaxies in 10 QSO fields that were not included in Paper I (Chen et al., 1998, Cat. <J/ApJ/498/77>) and near-infrared imaging observations of galaxies in 15 QSO fields.
- ID:
- ivo://CDS.VizieR/J/ApJ/740/91
- Title:
- Ly{alpha} and OVI in galaxies around quasars
- Short Name:
- J/ApJ/740/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the association of galaxies with Ly{alpha} and OVI absorption, the most commonly detected transitions of the low-z intergalactic medium (IGM), in the fields of 14 quasars with z_em_=0.06-0.57. Confirming previous studies, we observe a high covering fraction for Ly{alpha} absorption to impact parameter {rho}=300h^-1^_72_kpc: 33/37 of our L>0.01L* galaxies show Ly{alpha} equivalent width W^Ly{alpha}^>=50 m{AA}. Galaxies of all luminosity L>0.01L* and spectral type are surrounded by a diffuse and ionized circumgalactic medium (CGM), whose baryonic mass is estimated at ~10^10.5^+/-0.3M_{sun}_ for a constant N_H_=10^19^cm^-2^. The virialized halos and extended CGM of present-day galaxies are responsible for most strong Ly{alpha} absorbers (W^Ly{alpha}^>300m{AA}) but cannot reproduce the majority of observed lines in the Ly{alpha} forest. We conclude that the majority of Ly{alpha} absorption with W^Ly{alpha}^=30-300m{AA} occurs in the cosmic web predicted by cosmological simulations and estimate a characteristic width for these filaments of ~400h^-1^_72_kpc. Regarding OVI, we observe a near unity covering fraction to {rho}=200h^-1^_72_kpc for L>0.1L* galaxies and to {rho}=300h^-1^_72_kpc for sub-L* (0.1 L*<L<L*) galaxies. Similar to our Ly{alpha} results, stronger OVI systems (W^1031^>70m{AA}) arise in the virialized halos of L>0.1L* galaxies. Unlike Ly{alpha}, the weaker OVI systems (W^1031^~30m{AA}) arise in the extended CGM of sub-L* galaxies. The majority of OVI gas observed in the low-z IGM is associated with a diffuse medium surrounding individual galaxies with L~0.3L* and rarely originates in the so-called warm-hot IGM (predicted by cosmological simulations.
- ID:
- ivo://CDS.VizieR/J/ApJ/859/53
- Title:
- Ly{alpha} candidates from a MUSE survey of 6 AGNs
- Short Name:
- J/ApJ/859/53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent theoretical models suggest that the early phase of galaxy formation could involve an epoch when galaxies are gas rich but inefficient at forming stars: a "dark galaxy" phase. Here, we report the results of our Multi-Unit Spectroscopic Explorer (MUSE) survey for dark galaxies fluorescently illuminated by quasars at z>3. Compared to previous studies which are based on deep narrowband (NB) imaging, our integral field survey provides a nearly uniform sensitivity coverage over a large volume in redshift space around the quasars as well as full spectral information at each location. Thanks to these unique features, we are able to build control samples at large redshift distances from the quasars using the same data taken under the same conditions. By comparing the rest-frame equivalent width (EW0) distributions of the Ly{alpha} sources detected in proximity to the quasars and in control samples, we detect a clear correlation between the locations of high-EW0 objects and the quasars. This correlation is not seen in other properties, such as Ly{alpha} luminosities or volume overdensities, suggesting the possible fluorescent nature of at least some of these objects. Among these, we find six sources without continuum counterparts and EW0 limits larger than 240{AA} that are the best candidates for dark galaxies in our survey at z>3.5. The volume densities and properties, including inferred gas masses and star formation efficiencies, of these dark galaxy candidates are similar to those of previously detected candidates at z~2.4 in NB surveys. Moreover, if the most distant of these are fluorescently illuminated by the quasar, our results also provide a lower limit of t=60Myr on the quasar lifetime.
- ID:
- ivo://CDS.VizieR/J/ApJ/760/128
- Title:
- Ly{alpha} emission from 4<z<6 sources in COSMOS
- Short Name:
- J/ApJ/760/128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate spectroscopically measured Ly{alpha} equivalent widths (EWs) and escape fractions of 244 sources of which 95 are Lyman break galaxies (LBGs) and 106 Lyman alpha emitters (LAEs) at z~4.2, z~4.8, and z~5.6 selected from intermediate and narrowband observations. The sources were selected from the Cosmic Evolution Survey and observed with the DEIMOS spectrograph. We find that the distribution of EWs shows no evolution with redshift for both the LBG selected sources and the intermediate/narrowband LAEs. We also find that the Ly{alpha} escape fraction of intermediate/narrowband LAEs is on average higher and has a larger variation than the escape fraction of LBG selected sources. The escape fraction does not show a dependence with redshift. Similar to what has been found for LAEs at low redshifts, the sources with the highest extinctions show the lowest escape fractions. The range of escape fractions increases with decreasing extinction. This is evidence that the dust extinction is the most important factor affecting the escape of Ly{alpha} photons, but at low extinctions other factors, such as the H I covering fraction and gas kinematics, can be just as effective at inhibiting the escape of Ly{alpha} photons.
- ID:
- ivo://CDS.VizieR/J/ApJ/667/79
- Title:
- Ly{alpha} emission-line galaxies at z=3.1
- Short Name:
- J/ApJ/667/79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the results of an extremely deep, 0.28{deg}^2^ survey for z=3.1 Ly{alpha} emission-line galaxies in the Extended Chandra Deep Field-South. By using a narrowband 5000{AA} filter and complementary broadband photometry from the MUSYC survey, we identify a statistically complete sample of 162 galaxies with monochromatic fluxes brighter than 1.5x10^-17^ergs/cm^2^/s and observer's frame equivalent widths greater than 80{AA}
- ID:
- ivo://CDS.VizieR/J/PASJ/57/165
- Title:
- Ly{alpha} emitters in the SUBARU Deep Field
- Short Name:
- J/PASJ/57/165
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new results of a deep optical imaging survey using a narrow band filter (NB921) centered at {lambda}=9196{AA} together with B, V, R, i', and z' broadband filters in the sky area of the Subaru Deep Field, which has been promoted as one of legacy programs of the 8.2m Subaru Telescope. We obtained a photometric sample of 58 Ly{alpha} emitter candidates at z~6.5-6.6 among ~180 strong NB921-excess (z'-NB921>1.0) objects together with a color criterion of i'-z'>1.3. We then obtained optical spectra of 20 objects in our NB921-excess sample, and identified at least nine Ly{alpha} emitters at z~6.5-6.6, including the two emitters reported by Kodaira et al. (2003PASJ...55L..17K). Since our Ly{alpha}-emitter candidates are free from strong amplification of gravitational lensing, we are able to discuss their observational properties from a statistical point of view. Based on these new results, we obtained a lower limit of the star-formation rate density of rho_SFR_~5.7x10^-4^h_0.7_M_{sun}/yr/Mpc^3^ at z~6.6, being consistent with our previous estimate. We discuss the nature of star-formation activity in galaxies beyond z=6.
