Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userThe H-alpha Luminosity Function and Star Formation Rate Volume Density at z=0.8 from the NEWFIRM H-alpha Survey
273
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
[Abridged] We present new measurements of the H-alpha luminosity function (LF) and SFR volume density for galaxies at z~0.8. Our analysis is based on 1.18$mu$m narrowband data from the NEWFIRM H-alpha Survey, a comprehensive program designed to capture deep samples of intermediate redshift emission-line galaxies using narrowband imaging in the near-infrared. The combination of depth ($approx1.9times10^{-17}$ erg s$^{-1}$ cm$^{-2}$ in H-alpha at 3$sigma$) and areal coverage (0.82 deg$^2$) complements other recent H-alpha studies at similar redshifts, and enables us to minimize the impact of cosmic variance and place robust constraints on the shape of the LF. The present sample contains 818 NB118 excess objects, 394 of which are selected as H-alpha emitters. Optical spectroscopy has been obtained for 62% of the NB118 excess objects. Empirical optical broadband color classification is used to sort the remainder of the sample. A comparison of the LFs constructed for the four individual fields reveals significant cosmic variance, emphasizing that multiple, widely separated observations are required. The dust-corrected LF is well-described by a Schechter function with L*=10^{43.00pm0.52} ergs s^{-1}, phi*=10^{-3.20pm0.54} Mpc^{-3}, and alpha=-1.6pm0.19. We compare our H-alpha LF and SFR density to those at z<1, and find a rise in the SFR density propto(1+z)^{3.4}, which we attribute to significant L* evolution. Our H-alpha SFR density of 10^{-1.00pm0.18} M_sun yr^{-1} Mpc^{-3} is consistent with UV and [O II] measurements at z~1. We discuss how these results compare to other H-alpha surveys at z~0.8, and find that the different methods used to determine survey completeness can lead to inconsistent results. This suggests that future surveys probing fainter luminosities are needed, and more rigorous methods of estimating the completeness should be adopted as standard procedure.
rate research
Read More
To derive a new H$alpha$ luminosity function and to understand the clustering properties of star-forming galaxies at $z approx 0.24$, we have made a narrow-band imaging survey for H$alpha$ emitting galaxies in the HST COSMOS 2 square degree field. We used the narrow-band filter NB816 ($lambda_c = 8150$ AA, $Delta lambda = 120$ AA) and sampled H$alpha$ emitters with $EW_{rm obs}(rm Halpha + [Ntextsc{ii}]) > 12$ AA in a redshift range between $z=0.233$ and $z=0.251$ corresponding to a depth of 70 Mpc. We obtained 980 H$alpha$ emitting galaxies in a sky area of 5540 arcmin$^2$, corresponding to a survey volume of $3.1 times 10^4 {rm Mpc^3}$. We derive a H$alpha$ luminosity function with a best-fit Schechter function parameter set of $alpha = -1.35^{+0.11}_{-0.13}$, $logphi_* = -2.65^{+0.27}_{-0.38}$, and $log L_* ({rm erg s^{-1}}) = 41.94^{+0.38}_{-0.23}$. The H$alpha$ luminosity density is $2.7^{+0.7}_{-0.6} times 10^{39}$ ergs s$^{-1}$ Mpc$^{-3}$. After subtracting the AGN contribution (15 %) to the H$alpha$ luminosity density, the star formation rate density is evaluated as $1.8^{+0.7}_{-0.4} times 10^{-2}$ $M_{sun}$ yr$^{-1}$ Mpc$^{-3}$. The angular two-point correlation function of H$alpha$ emitting galaxies of $log L({rm Halpha}) > 39.8$ is well fit by a power law form of $w(theta) = 0.013^{+0.002}_{-0.001} theta^{-0.88 pm 0.03}$, corresponding to the correlation function of $xi(r) = (r/1.9{rm Mpc})^{-1.88}$. We also find that the H$alpha$ emitters with higher H$alpha$ luminosity are more strongly clustered than those with lower luminosity.
We present the spatially resolved H-alpha (Ha) dynamics of sixteen star-forming galaxies at z~0.81 using the new KMOS multi-object integral field spectrograph on the ESO VLT. These galaxies were selected using 1.18 um narrow-band imaging from the 10 deg^2 CFHT-HiZELS survey of the SA22hr field, are found in a ~4Mpc over-density of Ha emitters and likely reside in a group/intermediate environment, but not a cluster. We confirm and identify a rich group of star-forming galaxies at z=0.813+-0.003, with thirteen galaxies within 1000 km/s of each other, and 7 within a diameter of 3Mpc. All our galaxies are typical star-forming galaxies at their redshift, 0.8+-0.4 SFR*(z=0.8), spanning a range of specific star formation rate of sSFR=0.2-1.1 Gyr^-1 and have a median metallicity very close to solar of 12+log(O/H)=8.62+-0.06. We measure the spatially resolved Ha dynamics of the galaxies in our sample and show that thirteen out of sixteen galaxies can be described by rotating disks and use the data to derive inclination corrected rotation speeds of 50-275 km/s. The fraction of disks within our sample is 75+-8, consistent with previous results based on HST morphologies of Ha selected galaxies at z~1 and confirming that disks dominate the star formation rate density at z~1. Our Ha galaxies are well fitted by the z~1-2 Tully-Fisher relation, confirming the evolution seen in the zero-point. Apart from having, on average, higher stellar masses and lower sSFRs, our group galaxies at z=0.813 present the same mass-metallicity and TF relation as z~1 field galaxies, and are all disk galaxies.
We present clustering analyses of identically-selected star-forming galaxies in 3 narrow redshift slices (at z=0.8, z=1.47 and z=2.23), from HiZELS, a deep, near-infrared narrow-band survey. The HiZELS samples span the peak in the cosmic star-formation rate density, identifying typical star-forming galaxies at each epoch. Narrow-band samples have well-defined redshift distributions and are therefore ideal for clustering analyses. We quantify the clustering of the three samples, and of H-alpha luminosity-selected subsamples, initially using simple power law fits to the two-point correlation function. We extend this work to link the evolution of star-forming galaxies and their host dark matter halos over cosmic time using sophisticated dark matter halo models. We find that the clustering strength, r0, and the bias of galaxy populations relative to the clustering of dark matter increase linearly with H-alpha luminosity (and, by implication, star-formation rate) at all three redshifts, as do the host dark matter halo masses of the HiZELS galaxies. The typical galaxies in our samples are star-forming centrals, residing in halos of mass M_halo ~ a few times 10^12M_solar. We find a remarkably tight redshift-independent relation between the H-alpha luminosity scaled by the characteristic luminosity, L(H-alpha)/L(H-alpha)*(z), and the minimum host dark matter halo mass of central galaxies. This reveals that the dark matter halo environment is a strong driver of galaxy star-formation rate and therefore of the evolution of the star-formation rate density in the Universe.
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 $rho_{rm SFR}=0.012pm0.005 {rm text{M}_{odot} yr^{-1} Mpc^{-3}}$.
Using deep narrow-band and broad-band imaging, we identify 401 z~0.40 and 249 z~0.49 H-alpha line-emitting galaxies in the Subaru Deep Field. Compared to other H-alpha surveys at similar redshifts, our samples are unique since they probe lower H-alpha luminosities, are augmented with multi-wavelength (rest-frame 1000AA--1.5 microns) coverage, and a large fraction (20%) of our samples has already been spectroscopically confirmed. Our spectra allow us to measure the Balmer decrement for nearly 60 galaxies with H-beta detected above 5-sigma. The Balmer decrements indicate an average extinction of A(H-alpha)=0.7^{+1.4}_{-0.7} mag. We find that the Balmer decrement systematically increases with higher H-alpha luminosities and with larger stellar masses, in agreement with previous studies with sparser samples. We find that the SFRs estimated from modeling the spectral energy distribution (SED) is reliable---we derived an intrinsic H-alpha luminosity which is then reddened assuming the color excess from SED modeling. The SED-predicted H-alpha luminosity agrees with H-alpha narrow-band measurements over 3 dex (rms of 0.25 dex). We then use the SED SFRs to test different statistically-based dust corrections for H-alpha and find that adopting one magnitude of extinction is inappropriate: galaxies with lower luminosities are less reddened. We find that the luminosity-dependent dust correction of Hopkins et al. yields consistent results over 3 dex (rms of 0.3 dex). Our comparisons are only possible by assuming that stellar reddening is roughly half of nebular reddening. The strong correspondence argue that with SED modeling, we can derive reliable intrinsic SFRs even in the absence of H-alpha measurements at z~0.5.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
