- ID:
- ivo://CDS.VizieR/J/A+A/619/A136
- Title:
- VLT/X-SHOOTER spectrum of COLA1
- Short Name:
- J/A+A/619/A136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Distant luminous Lyman-{alpha} emitters (LAEs) are excellent targets for spectroscopic observations of galaxies in the epoch of reionisation (EoR). We present deep high-resolution (R=5000) VLT/X-shooter observations, along with an extensive collection of photometric data of COLA1, a proposed double peaked LAE at z=6.6. We rule out the possibility that COLA1's emission line is an [OII] doublet at z=1.475 on the basis of i) the asymmetric red line-profile and flux ratio of the peaks (blue/red=0.31+/-0.03) and ii) an unphysical [OII]/H{alpha} ratio ([OII]/H{alpha}>22). We show that COLA1's observed B-band flux is explained by a faint extended foreground LAE, for which we detect Ly{alpha} and [OIII] at z=2.142. We thus conclude that COLA1 is a real double-peaked LAE at z=6.593, the first discovered at z>6. COLA1 is UV luminous (M1500=-21.6+/-0.3), has a high equivalent width (EW0,Ly{alpha}=120_-40_^+50^{AA}) and very compact Ly{alpha} emission (r50,Ly{alpha}=0.33_-0.04_^+0.07^kpc). Relatively weak inferred H{beta}+[OIII] line-emission from Spitzer/IRAC indicates an extremely low metallicity of Z<1/20Z_{sun}_ or reduced strength of nebular lines due to high escape of ionising photons. The small Ly{alpha} peak separation of 220+/-20km/s implies a low HI column density and an ionising photon escape fraction of ~15-30%, providing the first direct evidence that such galaxies contribute actively to the reionisation of the Universe at z>6. Based on simple estimates, we find that COLA1 could have provided just enough photons to reionise its own ~0.3pMpc (2.3cMpc) bubble, allowing the blue Ly{alpha} line to be observed. However, we also discuss alternative scenarios explaining the detected double peaked nature of COLA1. Our results show that future high-resolution observations of statistical samples of double peaked LAEs at z>5 are a promising probe of the occurrence of ionised regions around galaxies in the EoR.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/634/A97
- Title:
- VUDS UV and Ly{alpha} luminosity functions
- Short Name:
- J/A+A/634/A97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The star formation rate density (SFRD) evolution presents an area of great interest in the studies of galaxy evolution and reionization. The current constraints of SFRD at z>5 are based on the rest-frame UV luminosity functions with the data from photometric surveys. The VIMOS UltraDeep Survey (VUDS) was designed to observe galaxies at redshifts up to ~6 and opened a window for measuring SFRD at z>5 from a spectroscopic sample with a well-controlled selection function. We establish a robust statistical description of the star-forming galaxy population at the end of cosmic HI reionization (5.0<=z<=6.6) from a large sample of 49 galaxies with spectroscopically confirmed redshifts. We determine the rest-frame UV and Ly{alpha} luminosity functions and use them to calculate SFRD at the median redshift of our sample z=5.6. We selected a sample of galaxies at 5.0<=z_spec_<=6.6 from the VUDS. We cleaned our sample from low redshift interlopers using ancillary photometric data. We identified galaxies with Ly{alpha} either in absorption or in emission, at variance with most spectroscopic samples in the literature where Ly{alpha} emitters (LAE) dominate. We determined luminosity functions using the 1/V_max_ method. The galaxies in this redshift range exhibit a large range in their properties. A fraction of our sample shows strong Ly{alpha} emission, while another fraction shows Ly{alpha} in absorption. UV-continuum slopes vary with luminosity, with a large dispersion. We find that star-forming galaxies at these redshifts are distributed along the main sequence in the stellar mass vs. SFR plane, described with a slope {alpha}=0.85+/-0.05. We report a flat evolution of the specific SFR compared to lower redshift measurements. We find that the UV luminosity function is best reproduced by a double power law, while a fit with a Schechter function is only marginally inferior. The Ly{alpha} luminosity function is best fitted with a Schechter function. We derive a logSFRD_UV_(M_{sun}_/yr/Mpc^3^)=-1.45^+0.06^_-0.08_ and logSFRD_Ly{alpha}_(M_{sun}_/yr/Mpc^3^)=-1.40^+0.07^_-0.08_. The SFRD derived from the Ly{alpha} luminosity function is in excellent agreement with the UV-derived SFRD after correcting for IGM absorption.Conclusions. Our new SFRD measurements at a mean redshift of z=5.6 are ~0.2dex above the mean SFRD reported in Madau & Dickinson (2014ARA&A..52..415M), but in excellent agreement with results from Bouwens et al. (2015ApJ...803...34B). These measurements confirm the steep decline of the SFRD at z>2. The bright end of the Ly{alpha} luminosity function has a high number density, indicating a significant star formation activity concentrated in the brightest LAE at these redshifts. LAE with equivalent width EW>25{AA} contribute to about 75% of the total UV-derived SFRD. While our analysis favors low dust content in 5.0<z<6.6, uncertainties on the dust extinction correction and associated degeneracy in spectral fitting will remain an issue, when estimating the total SFRD until future surveys extending spectroscopy to the NIR rest-frame spectral domain, such as with JWST.
- ID:
- ivo://CDS.VizieR/J/A+A/609/A34
- Title:
- VUV absorption cross section of CO_2_
- Short Name:
- J/A+A/609/A34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We quantify the temperature dependency of the VUV absorption cross section of carbon dioxide. The VUV absorption cross section of CO_2_ increases with the temperature. The absorption we measured at 150K seems to be close to the absorption of CO_2_ in the fundamental ground state. The absorption cross section can be separated in two parts: a continuum and a fine structure superimposed on the continuum. The variation of the continuum of absorption can be represented by the sum of three gaussian functions. We used these data in our 1D thermo-photochemical model in order to study their impact on the predicted atmospheric composition of warm exoplanets. Using data at high temperature in thermo-photochemical models modifies significantly the abundance and the photodissociation rates of many species, in addition to carbon dioxide, such as methane and ammonia. These deviations have an impact on synthetic transmission spectra, leading to variations of up to 5ppm.
- ID:
- ivo://CDS.VizieR/III/130
- Title:
- Wavelength Dependence of Galactic UV Extinction
- Short Name:
- III/130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A collection of data for 115 extinction curves derived from low-dispersion IUE spectra are presented with normalization to E(B-V)=1. The electronic Atlas of Extinctions contains the list of the stars used, their association membership, and the normalized extinctions for 88 wavelength values between 1260 and 3000 Angstroems.
- ID:
- ivo://CDS.VizieR/J/MNRAS/449/4204
- Title:
- WFC3/UVIS quasar-stacked spectrum at z=~2.4
- Short Name:
- J/MNRAS/449/4204
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ionizing continuum from active galactic nuclei is fundamental for interpreting their broad emission lines and understanding their impact on the surrounding gas. Furthermore, it provides hints on how matter accretes on to supermassive black holes. Using Hubble Space Telescope's Wide Field Camera 3, we have constructed the first stacked ultraviolet (rest-frame wavelengths 600-2500{AA}) spectrum of 53 luminous quasars at z=~2.4, with a state-of-the-art correction for the intervening Lyman forest and Lyman continuum absorption. The continuum slope (f_{nu}_{prop.to}{nu}^{alpha}{nu}^) of the full sample shows a break at ~912{AA} with spectral index {alpha}_{nu}_=-0.61+/-0.01 at {lambda}>912{AA} and a softening at shorter wavelengths ({alpha}_{nu}_=-1.70+/-0.61 at {lambda}<=912{AA}). Our analysis proves that a proper intergalactic medium absorption correction is required to establish the intrinsic continuum emission of quasars. We interpret our average ultraviolet spectrum in the context of photoionization, accretion disc models, and quasar contribution to the ultraviolet background. We find that observed broad line ratios are consistent with those predicted assuming an ionizing slope of {alpha}_ion_=-2.0, similar to the observed ionizing spectrum in the same wavelength range. The continuum break and softening are consistent with accretion disc plus X-ray corona models when black hole spin is taken into account. Our spectral energy distribution yields a 30 per cent increase to previous estimates of the specific quasar emissivity, such that quasars may contribute significantly to the total specific Lyman limit emissivity estimated from the Ly{alpha} forest at z<3.2.
- ID:
- ivo://CDS.VizieR/J/ApJ/714/1037
- Title:
- White dwarfs from the Kiso survey
- Short Name:
- J/ApJ/714/1037
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic analysis of white dwarfs found in the Kiso survey. Spectroscopic observations at high signal-to-noise ratio have been obtained for all DA and DB stars in the Kiso Schmidt ultraviolet excess survey (KUV stars). These observations led to the reclassification of several KUV objects, including the discovery of three unresolved DA+DB double-degenerate binaries. The atmospheric parameters (T_eff_ and logg) are obtained from detailed model atmosphere fits to optical spectroscopic data. The mass distribution of our sample is characterized by a mean value of 0.606M_{sun}_ and a dispersion of 0.135M_{sun}_ for DA stars, and 0.758M_{sun}_ and a dispersion of 0.192M_{sun}_ for DB stars. Absolute visual magnitudes obtained from our spectroscopic fits allow us to derive an improved luminosity function for the DA and DB stars identified in the Kiso survey. Our luminosity function is found to be significantly different from earlier estimates based on empirical photometric calibrations of M_V_ for the same sample. The results for the DA stars now appear entirely consistent with those obtained for the PG survey using the same spectroscopic approach. The space density for DA stars with M_V_<=12.75 is 2.80x10^-4^pc^-3^ in the Kiso survey, which is 9.6% smaller than the value found in the PG survey.
- ID:
- ivo://CDS.VizieR/VI/105
- Title:
- Wisconsin Ultraviolet Photo-Polarimeter Experiment
- Short Name:
- VI/105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Wisconsin Ultraviolet Photo-Polarimeter Experiment WUPPE was one of three ultraviolet telescopes on the ASTRO-1 mission flown on the space shuttle Columbia during 2-10 December, 1990. 98 observations of 75 targets were obtained. The same three instruments were later flown on the space shuttle Endeavour from 3-17 March, 1995, as part of the ASTRO-2 mission. During the longer ASTRO-2 mission, 369 observations of 254 targets were obtained.
- ID:
- ivo://CDS.VizieR/J/ApJ/866/44
- Title:
- WISE/DEIMOS Redshift Catalog DR2 & extended data
- Short Name:
- J/ApJ/866/44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The WISE satellite surveyed the entire sky multiple times in four infrared (IR) wavelengths (3.4, 4.6, 12, and 22{mu}m). This all-sky IR photometric survey makes it possible to leverage many of the large publicly available spectroscopic redshift surveys to measure galaxy properties in the IR. While characterizing the cross-matching of WISE data to a single survey is a straightforward process, doing it with six different redshift surveys takes a fair amount of space to characterize adequately, because each survey has unique caveats and characteristics that need addressing. This work describes a data set that results from matching five public redshift surveys with the AllWISE data release, along with a reanalysis of the data described in Lake+ (2012, J/AJ/143/7). The combined data set has an additional flux limit of 80{mu}Jy (19.14 AB mag) in WISE's W1 filter, imposed in order to limit it to targets with high completeness and reliable photometry in the AllWISE data set. Consistent analysis of all of the data is only possible if the color bias discussed in Ilbert+ (2004MNRAS.351..541I) is addressed (e.g., the techniques explored in Lake+ 2017AJ....153..189L). The sample defined herein is used in a companion paper in this series to measure the luminosity function of galaxies at 2.4{mu}m rest-frame wavelength, and the selection process of the sample is optimized for this purpose.
- ID:
- ivo://CDS.VizieR/J/A+A/539/A48
- Title:
- XMM AGN optical-UV luminosities
- Short Name:
- J/A+A/539/A48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Active galactic nuclei (AGN) emit radiation over a wide range of wavelengths, with a peak of emission in the far-UV region of the electromagnetic spectrum, a spectral region that is historically difficult to observe. Using optical, GALEX UV, and XMM-Newton data we derive the spectral energy distribution (SED) from the optical/UV to X-ray regime of a sizeable sample of AGN. The principal motivation is to investigate the relationship between the optical/UV emission and the X-ray emission and provide bolometric corrections to the hard X-ray (2-10keV) energy range, k_bol_, the latter being a fundamental parameter in current physical cosmology.
490. XMMOMCDFS catalogue
- ID:
- ivo://CDS.VizieR/J/A+A/574/A49
- Title:
- XMMOMCDFS catalogue
- Short Name:
- J/A+A/574/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The XMM-Newton X-ray observatory has performed repeated observations of the CDFS in 33 epochs (2001-2010) through the XMM-CDFS Deep Survey. During the X-ray observations, XMM-OM targeted the central 17x17arcmin^2^ region of the X-ray field of view, providing simultaneous optical/UV coverage of the CDFS. The resulting set of data can be taken into account to build an XMM-OM catalogue of the CDFS, filling the UV spectral coverage between the optical surveys and GALEX observations. We present the UV catalogue of the XMM-CDFS Deep Survey. Its main purpose is to provide complementary UV average photometric measurements of known optical/UV sources in the CDFS, taking advantage of the unique characteristics of the survey. The data reduction is intended also to improve the standard source detection on individual observations, by cataloguing faint sources through the stacking of their exposure images. We reprocessed the XMM-OM data of the survey and we stacked the exposures from consecutive observations using the standard SAS tools to process the data obtained during single observations. Average measurements of detections with SAS good quality flags from individual observations and from stacked images have been joined to compile the catalogue. Sources have been validated through the cross-identification within the EIS and COMBO-17 surveys. Photometric data of 1129 CDFS sources are provided into the catalogue, and optical/UV/X-ray photometric and spectroscopic information from other surveys are also included. The stacking extends the detection limits by ~1 mag in the three UV bands, contributing 30% of the catalogued UV sources. The comparison with the available measurements in similar spectral bands confirms the validity of the XMM-OM calibration. The combined COMBO-17/X-ray classification of the "intermediate" sources (e.g. optically diluted and/or X-ray absorbed AGN) is also discussed.
