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Register a new userThe OTELO survey. A case study of [O III]4959,5007 emitters at <z> = 0.83
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The OTELO survey is a very deep, blind exploration of a selected region of the Extended Groth Strip and is designed for finding emission-line sources (ELSs). The survey design, observations, data reduction, astrometry, and photometry, as well as the correlation with ancillary data used to obtain a final catalogue, including photo-z estimates and a preliminary selection of ELS, were described in a previous contribution. Here, we aim to determine the main properties and luminosity function (LF) of the [O III] ELS sample of OTELO as a scientific demonstration of its capabilities, advantages, and complementarity with respect to other surveys. The selection and analysis procedures of ELS candidates obtained using tunable filter (TF) pseudo-spectra are described. We performed simulations in the parameter space of the survey to obtain emission-line detection probabilities. Relevant characteristics of [O III] emitters and the LF([O III]), including the main selection biases and uncertainties, are presented. A total of 184 sources were confirmed as [O III] emitters at a mean redshift z=0.83. The minimum detectable line flux and equivalent width (EW) in this ELS sample are $sim$5 $times$ 10$^{-19}$ erg s$^{-1}$ cm$^{2}$ and $sim$6 AA, respectively. We are able to constrain the faint-end slope ($alpha = -1.03pm0.08$) of the observed LF([O III]) at z=0.83. This LF reaches values that are approximately ten times lower than those from other surveys. The vast majority (84%) of the morphologically classified [O III] ELSs are disc-like sources, and 87% of this sample is comprised of galaxies with stellar masses of M$_star$ $<$ 10$^{10}$ M$_{odot}$.
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We take advantage of the capabilities of the OTELO survey to select and study the AGN population in the field. We performed an analysis of the properties of these objects, including their demography, morphology, and IR luminosity. Focusing on the population of H$alpha$ emitters at $z sim 0.4$, we also aim to study the environments of AGN and non-AGN galaxies at that redshift. We make use of the multiwavelength catalog of objects in the field compiled by the OTELO survey, unique in terms of minimum line flux and equivalent width. The OTELO pseudo-spectra allow the identification of emission lines and the spectral classification of the sources. We obtained a sample of 72 AGNs in the field of OTELO, selected with four different methods in the optical, X-rays, and mid-infrared bands. We find that using X-rays is the most efficient way to select AGNs. An analysis was performed on the AGN population of OTELO in order to characterize its members. At $z sim 0.4$, we find that up to 26% of our H$alpha$ emitters are AGNs. At that redshift, AGNs are found in identical environments to non-AGNs, although they represent the most clustered group when compared to passive and star-forming galaxies. The majority of our AGNs at any redshift were classified as late-type galaxies, including a 16% proportion of irregulars. Another 16% of AGNs show signs of interactions or mergers. Regarding the infrared luminosity, we are able to recover all the luminous infrared galaxies (LIRGs) in the field of OTELO up to $zsim 1.6$. We find that the proportion of LIRGs and ultra-luminous infrared galaxies (ULIRGs) is higher among the AGN population, and that ULIRGs show a higher fraction of AGNs than LIRGs.
We take advantage of the capability of the OTELO survey to obtain the H$alpha$ luminosity function (LF) at ${rm z}sim0.40$. Because of the deepest coverage of OTELO, we are able to determine the faint end of the LF, and thus better constrain the star formation rate and the number of galaxies at low luminosities. The AGN contribution to this LF is estimated as well. We make use of the multi-wavelength catalogue of objects in the field compiled by the OTELO survey, which is unique in terms of minimum flux and equivalent width. We also take advantage of the pseudo-spectra built for each source, which allow the identification of emission lines and the discrimination of different types of objects. The H$alpha$ luminosity function at $zsim0.40$ is obtained, which extends the current faint end by almost 1 dex, reaching minimal luminosities of $log_{10}L_{rm lim}=38.5$ erg s$^{-1}$ (or $sim0.002, text{M}_odottext{ yr}^{-1})$. The AGN contribution to the total H$alpha$ luminosity is estimated. We find that no AGN should be expected below a luminosity of $log_{10}L=38.6$ erg s$^{-1}$. From the sample of non-AGN (presumably, pure SFG) at $zsim0.40$ we estimated a star formation rate density of $rho_{rm SFR}=0.012pm0.005 {rm text{M}_{odot} yr^{-1} Mpc^{-3}}$.
We present a result of a blind search for [CII] 158 $mu$m emitters at $zsim 4.5$ using ALMA Cycle~0 archival data. We collected extra-galactic data covering at 330-360 GHz (band~7) from 8 Cycle~0 projects from which initial results have been already published. The total number of fields is 243 and the total on-source exposure time is 19.2 hours. We searched for line emitters in continuum-subtracted data cubes with spectral resolutions of 50, 100, 300 and 500 km/s. We could not detect any new line emitters above a 6-$sigma$ significance level. This result provides upper limits to the [CII] luminosity function at $zsim 4.5$ over $L_{rm [CII]} sim 10^8 - 10^{10} L_{odot}$ or star formation rate, SFR $sim$ 10-1000 M$_{^odot}$/yr. These limits are at least 2 orders of magnitude larger than the [CII] luminosity functions expected from the $z sim 4$ UV luminosity function or from numerical simulation. However, this study demonstrates that we would be able to better constrain the [CII] luminosity function and to investigate possible contributions from dusty galaxies to the cosmic star-formation rate density by collecting Cycle~1+2 archival data as the ALMA Patchy Deep Survey.
A study of [S III]$lambdalambda9096,9532$ emitters at $z$ = 1.34 and 1.23 is presented using our deep narrow-band $H_2S1$ (centered at 2.13 $mu$m) imaging survey of the Extended Chandra Deep Field South (ECDFS). We combine our data with multi-wavelength data of ECDFS to build up spectral energy distributions (SEDs) from the $U$ to the $K_{s}$-band for emitter candidates selected with strong excess in $H_2S1 - K_{s}$ and derive photometric redshifts, line luminosities, stellar masses and extinction. A sample of 14 [S III] emitters are identified with $H_2S1<22.8$ and $K_{rm s}<24.8$ (AB) over 381 arcmin$^{2}$ area, having [S III] line luminosity $L_{[SIII]}= sim 10^{41.5-42.6}$erg s$^{-1}$. None of the [S III] emitters is found to have X-ray counterpart in the deepest Chandra 4 Ms observation, suggesting that they are unlikely powered by AGN. HST/ACS F606W and HST/WFC3 F160W images show their rest-frame UV and optical morphologies. About half of the [S III] emitters are mergers and at least one third are disk-type galaxies. Nearly all [S III] emitters exhibit a prominent Balmer break in their SEDs, indicating the presence of a significant post-starburst component. Taken together, our results imply that both shock heating in post-starburst and photoionization caused by young massive stars are likely to excite strong [S III] emission lines. We conclude that the emitters in our sample are dominated by star-forming galaxies with stellar mass $8.7<log (M/M_{sun})<9.9$.
We present new estimates of the luminosity function (LF) and star formation rate density (SFRD) for an H$alpha$ selected sample at $zsim0.62$ from the Deep And Wide Narrow-band (DAWN) survey. Our results are based on a new H$alpha$ sample in the extended COSMOS region (compared to Coughlin et al. 2018) with the inclusion of flanking fields, resulting in a total area coverage of $sim$1.5 deg$^2$. A total of 241 H$alpha$ emitters were selected based on robust selection criteria using spectro-photometric redshifts and broadband color-color classification. We explore the effect of different dust correction prescriptions by calculating the LF and SFRD using a constant dust extinction correction, A{$_{textrm{H}alpha}=1$} mag, a luminosity-dependent correction, and a stellar-mass dependent correction. The resulting H$alpha$ LFs are well fitted using Schechter functions with best-fit parameters: L$^*=10^{42.24}$ erg s$^{-1}$, $phi^*=10^{-2.85}$ Mpc$^{-3}$, $alpha = -1.62$ for constant dust correction, L$^*=10^{42.31}$ erg s$^{-1}$, $phi^*=10^{-2.8}$ Mpc$^{-3}$, $alpha=-1.39$ for luminosity-dependent dust correction, and L$^*=10^{42.36}$ erg s$^{-1}$, $phi^*=10^{-2.91}$ Mpc$^{-3}$, $alpha = -1.48$, for stellar mass-dependent dust correction. The deep and wide nature of the DAWN survey effectively samples H$alpha$ emitters over a wide range of luminosities, thereby providing better constraints on both the faint and bright end of the LF. Also, the SFRD estimates $rho_{textrm{SFR}}=10^{-1.39}$ M$_{odot}$yr$^{-1}$Mpc$^{-3}$ (constant dust correction), $rho_{textrm{SFR}}=10^{-1.47}$ M$_{odot}$yr$^{-1}$Mpc$^{-3}$ (luminosity-dependent dust correction), and $rho_{textrm{SFR}}=10^{-1.49}$ M$_{odot}$yr$^{-1}$Mpc$^{-3}$ (stellar mass-dependent dust correction) are in good agreement with the evolution of SFRD across redshifts ($0 < z < 2$) seen from previous H$alpha$ surveys.
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