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Register a new userThe OTELO survey. II. The faint-end of the H$alpha$ luminosity function at z $sim$ 0.40
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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 $rho_{rm SFR}=0.012pm0.005 {rm text{M}_{odot} yr^{-1} Mpc^{-3}}$.
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We present the quasar luminosity function at $z sim 5$ derived from the optical wide-field survey data obtained as a part of the Subaru strategic program (SSP) with Hyper Suprime-Cam (HSC). From $sim$81.8 deg$^2$ area in the Wide layer of the HSC-SSP survey, we selected 224 candidates of low-luminosity quasars at $z sim 5$ by adopting the Lyman-break method down to $i = 24.1$ mag. Based on our candidates and spectroscopically-confirmed quasars from the Sloan Digital Sky Survey (SDSS), we derived the quasar luminosity function at $z sim 5$ covering a wide luminosity range of $-28.76 < M_{rm 1450} < -22.32$ mag. We found that the quasar luminosity function is fitted by a double power-law model with a break magnitude of $M^{*}_{1450} = -25.05^{+0.10}_{-0.24}$ mag. The inferred number density of low-luminosity quasars is lower, and the derived faint-end slope, $-1.22^{+0.03}_{-0.10}$, is flatter than those of previous studies at $z sim 5$. A compilation of the quasar luminosity function at $4 leq z leq 6$ from the HSC-SSP suggests that there is little redshift evolution in the break magnitude and in the faint-end slope within this redshift range, although previous studies suggest that the faint-end slope becomes steeper at higher redshifts. The number density of low-luminosity quasars decreases more rapidly from $z sim 5$ to $z sim 6$ than from $z sim 4$ to $z sim 5$.
Aims. We aim to study the 250 micron luminosity function (LF) down to much fainter luminosities than achieved by previous efforts. Methods. We developed a modified stacking method to reconstruct the 250 micron LF using optically selected galaxies from the SDSS survey and Herschel maps of the GAMA equatorial fields and Stripe 82. Our stacking method not only recovers the mean 250 micron luminosities of galaxies that are too faint to be individually detected, but also their underlying distribution functions. Results. We find very good agreement with previous measurements in the overlapping luminosity range. More importantly, we are able to derive the LF down to much fainter luminosities (around 25 times fainter) than achieved by previous studies. We find strong positive luminosity evolution propto (1 + z)^4.89pm1.07 and moderate negative density evolution propto (1 + z)^-1.02pm0.54 over the redshift range z=[0.02, 0.5].
We present the results obtained with VLT/MUSE on the faint-end of the Lyman-alpha luminosity function (LF) based on deep observations of four lensing clusters. The precise aim of the present study is to further constrain the abundance of Lyman-alpha emitters (LAEs) by taking advantage of the magnification provided by lensing clusters. We blindly selected a sample of 156 LAEs, with redshifts between $2.9 le z le 6.7$ and magnification-corrected luminosities in the range $ 39 lesssim log L_{Ly_{alpha}}$ [erg s$^{-1}$] $lesssim 43$. The price to pay to benefit from magnification is a reduction of the effective volume of the survey, together with a more complex analysis procedure. To properly take into account the individual differences in detection conditions (including lensing configurations, spatial and spectral morphologies) when computing the LF, a new method based on the 1/Vmax approach was implemented. The LAE LF has been obtained in four different redshift bins with constraints down to $log L_{Ly_{alpha}} = 40.5$. From our data only, no significant evolution of LF mean slope can be found. When performing a Schechter analysis including data from the literature to complete the present sample a steep faint-end slope was measured varying from $alpha = -1.69^{+0.08}_{-0.08}$ to $alpha = -1.87^{+0.12}_{-0.12}$ between the lowest and the highest redshift bins. The contribution of the LAE population to the star formation rate density at $z sim 6$ is $lesssim 50$% depending on the luminosity limit considered, which is of the same order as the Lyman-break galaxy (LBG) contribution. The evolution of the LAE contribution with redshift depends on the assumed escape fraction of Lyman-alpha photons, and appears to slightly increase with increasing redshift when this fraction is conservatively set to one. (abridged)
We have conducted a spectroscopic survey to find faint quasars (-26.0 < M_{1450} < -22.0) at redshifts z=3.8-5.2 in order to measure the faint end of the quasar luminosity function at these early times. Using available optical imaging data from portions of the NOAO Deep Wide-Field Survey and the Deep Lens Survey, we have color-selected quasar candidates in a total area of 3.76 deg^2. Thirty candidates have R <= 23 mags. We conducted spectroscopic followup for 28 of our candidates and found 23 QSOs, 21 of which are reported here for the first time, in the 3.74 < z <5.06 redshift range. We estimate our survey completeness through detailed Monte Carlo simulations and derive the first measurement of the density of quasars in this magnitude and redshift interval. We find that the binned luminosity function is somewhat affected by the K-correction used to compute the rest-frame absolute magnitude at 1450A. Considering only our R <= 23 sample, the best-fit single power-law (Phi propto L^beta) gives a faint-end slope beta = -1.6+/-0.2. If we consider our larger, but highly incomplete sample going one magnitude fainter, we measure a steeper faint-end slope -2 < beta < -2.5. In all cases, we consistently find faint-end slopes that are steeper than expected based on measurements at z ~ 3. We combine our sample with bright quasars from the Sloan Digital Sky Survey to derive parameters for a double-power-law luminosity function. Our best fit finds a bright-end slope, alpha = -2.4+/-0.2, and faint-end slope, beta = -2.3+/-0.2, without a well-constrained break luminosity. This is effectively a single power-law, with beta = -2.7+/-0.1. We use these results to place limits on the amount of ultraviolet radiation produced by quasars and find that quasars are able to ionize the intergalactic medium at these redshifts.
We present spectroscopic observations obtained with the ESO Very Large Telecope (VLT) of seven candidate Ly-alpha emitting galaxies in the field of the radio quiet Q1205-30 at z=3.04 previously detected with deep narrow band imaging. Based on equivalent widths and limits on line ratios we confirm that all seven objects are Ly-alpha emitting galaxies. Deep images also obtained with the VLT in the B and I bands show that five of the seven galaxies have very faint continuum fluxes (I(AB) approx. 26.8 and B(AB) approx. 27.3). The star formation rates of these seven galaxies estimated from the rest-frame UV continuum around 2000AA, as probed by the I-band detections, as well as from the Ly-alpha luminosities, are 1-4 M_sun yr^{-1}. This is 1-3 orders of magnitude lower than for other known populations of star-forming galaxies at similar redshifts (the Lyman-Break galaxies and the sub-mm selected sources). The inferred density of the objects is high, 16+-4 per arcmin^2 per unit redshift. This is consistent with the integrated luminosity function for Lyman-Break galaxies down to R=27 if the fraction of Ly-alpha emitting galaxies is approx. 70% at the faint end of the luminosity function. However, if this fraction is 20% as reported for the bright end of the luminosity function then the space density in this field is significantly larger (by a factor of 3.5) than expected from the luminosity function for Lyman-Break galaxies in the HDF-North. This would be an indication that at least some radio quiet QSOs at high redshift reside in overdense environments or that the faint end slope of the high redshift luminosity function has been underestimated. These observations show that Ly-alpha emission is an efficient method by which to probe the faint end of the luminosity function at high redshifts.
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