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Register a new userAngular clustering and host halo properties of [OII] emitters at $z >1$ in the Subaru HSC survey
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We study the angular correlation function of star-forming galaxies and properties of their host dark matter halos at z>1 using the Hyper-Suprime Cam (HSC) SSP survey. We use [OII] emitters identified using two narrow-band (NB) filters, NB816 and NB921, in the Deep/UltraDeep layers, which respectively cover large angular areas of 16.3 deg^2 and 16.9 deg^2. Our sample contains 8302 and 9578 [OII] emitters at z=1.19 (NB816) and z=1.47 (NB921), respectively. We detect a strong clustering signal over a wide angular range, 0.001 < theta < 1 [deg], with the bias $b=1.61^{+0.13}_{-0.11}$ (z=1.19) and $b=2.09^{+0.17}_{-0.15}$ (z=1.47). We also find a clear deviation of the correlation from a simple power-law form. To interpret the measured clustering signal, we adopt a halo occupation distribution (HOD) model that is constructed to explain the spatial distribution of galaxies selected by a star formation rate. The observed correlation function and number density are simultaneously explained by the best-fitting HOD model. From the constrained HOD model, the average mass of halos hosting the [OII] emitters is derived to be $log{M_{eff}/(h^{-1}M_odot)}=12.70^{+0.09}_{-0.07}$ and $12.61^{+0.09}_{-0.05}$ at z=1.19 and 1.47, respectively, which will become halos with the present-day mass, $Msim 1.5 times 10^{13}h^{-1}M_odot$. The satellite fraction of the [OII] emitter sample is found to be $f_{sat}sim 0.15$. All these values are consistent with the previous studies of similar samples, but we obtain tighter constraints even in a larger parameter space due to the larger sample size from the HSC. The results obtained for host halos of [OII] emitters in this paper enable the construction of mock galaxy catalogs and the systematic forecast study of cosmological constraints from upcoming emission line galaxy surveys such as the Subaru PFS survey.
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Emission line galaxies (ELGs) are used in several ongoing and upcoming surveys (SDSS-IV/eBOSS, DESI) as tracers of the dark matter distribution. Using a new galaxy formation model, we explore the characteristics of [OII] emitters, which dominate optical ELG selections at $zsimeq 1$. Model [OII] emitters at $0.5<z<1.5$ are selected to mimic the DEEP2, VVDS, eBOSS and DESI surveys. The luminosity functions of model [OII] emitters are in reasonable agreement with observations. The selected [OII] emitters are hosted by haloes with $M_{rm halo}geq 10^{10.3}h^{-1}{rm M}_{odot}$, with ~90% of them being central star-forming galaxies. The predicted mean halo occupation distributions of [OII] emitters has a shape typical of that inferred for star-forming galaxies, with the contribution from central galaxies, $langle N rangle_{left[OIIright], cen}$, being far from the canonical step function. The $langle N rangle_{left[OIIright], cen}$ can be described as the sum of an asymmetric Gaussian for disks and a step function for spheroids, which plateaus below unity. The model [OII] emitters have a clustering bias close to unity, which is below the expectations for eBOSS and DESI ELGs. At $zsim 1$, a comparison with observed g-band selected galaxy, which are expected to be dominated by [OII] emitters, indicates that our model produces too few [OII] emitters that are satellite galaxies. This suggests the need to revise our modelling of hot gas stripping in satellite galaxies.
We present the clustering properties of low-$z$ $(zleq1.4)$ galaxies selected by the Hyper Suprime-Cam Subaru Strategic Program Wide layer over $145$ deg$^{2}$. The wide-field and multi-wavelength observation yields $5,064,770$ galaxies at $0.3leq zleq1.4$ with photometric redshifts and physical properties. This enables the accurate measurement of angular correlation functions and subsequent halo occupation distribution (HOD) analysis allows the connection between baryonic properties and dark halo properties. The fraction of less-massive satellite galaxies at $zlesssim1$ is found to be almost constant at $sim20%$, but it gradually decreases beyond $M_{star} sim 10^{10.4}h^{-2}M_{odot}$. However, the abundance of satellite galaxies at $z>1$ is quite small even for less-massive galaxies due to the rarity of massive centrals at high-$z$. This decreasing trend is connected to the small satellite fraction of Lyman break galaxies at $z>3$. The stellar-to-halo mass ratios at $0.3leq zleq1.4$ are almost consistent with the predictions obtained using the latest empirical model; however, we identify small excesses from the theoretical model at the massive end. The pivot halo mass is found to be unchanged at $10^{11.9-12.1}h^{-1}M_{odot}$ at $0.3leq zleq1.4$, and we systematically show that $10^{12}h^{-1}M_{odot}$ is a universal pivot halo mass up to $zsim5$ that is derived using only the clustering/HOD analyses. Nevertheless, halo masses with peaked instantaneous baryon conversion efficiencies are much smaller than the pivot halo mass regardless of a redshift, and the most efficient stellar-mass assembly is thought to be in progress in $10^{11.0-11.5}h^{-1}M_{odot}$ dark haloes.
We present the SILVERRUSH program strategy and clustering properties investigated with $sim 2,000$ Ly$alpha$ emitters at $z=5.7$ and $6.6$ found in the early data of the Hyper Suprime-Cam (HSC) Subaru Strategic Program survey exploiting the carefully designed narrowband filters. We derive angular correlation functions with the unprecedentedly large samples of LAEs at $z=6-7$ over the large total area of $14-21$ deg$^2$ corresponding to $0.3-0.5$ comoving Gpc$^2$. We obtain the average large-scale bias values of $b_{rm avg}=4.1pm 0.2$ ($4.5pm 0.6$) at $z=5.7$ ($z=6.6$) for $gtrsim L^*$ LAEs, indicating the weak evolution of LAE clustering from $z=5.7$ to $6.6$. We compare the LAE clustering results with two independent theoretical models that suggest an increase of an LAE clustering signal by the patchy ionized bubbles at the epoch of reionization (EoR), and estimate the neutral hydrogen fraction to be $x_{rm HI}=0.15^{+0.15}_{-0.15}$ at $z=6.6$. Based on the halo occupation distribution models, we find that the $gtrsim L^*$ LAEs are hosted by the dark-matter halos with the average mass of $log (left < M_{rm h} right >/M_odot) =11.1^{+0.2}_{-0.4}$ ($10.8^{+0.3}_{-0.5}$) at $z=5.7$ ($6.6$) with a Ly$alpha$ duty cycle of 1 % or less, where the results of $z=6.6$ LAEs may be slightly biased, due to the increase of the clustering signal at the EoR. Our clustering analysis reveals the low-mass nature of $gtrsim L^*$ LAEs at $z=6-7$, and that these LAEs probably evolve into massive super-$L^*$ galaxies in the present-day universe.
We present the clustering analysis of photometric luminous red galaxies (LRGs) at a redshift range of $0.1leq z leq 1.05$ using $615,317$ photometric LRGs selected from the Hyper Suprime-Cam Subaru Strategic Program covering $sim124$ deg$^{2}$. Our sample covers a broad range of stellar masses and photometric redshifts and enables a halo occupation distribution analysis to study the redshift and stellar-mass dependence of dark halo properties of LRGs. We find a tight correlation between the characteristic dark halo mass to host central LRGs, $M_{min}$, and the number density of LRGs independently of redshifts, indicating that the formation of LRGs is associated with the global environment. The $M_{min}$ of LRGs depends only weakly on the stellar mass $M_{star}$ at $M_{star} lesssim 10^{10.75}h^{-2} M_{odot}$ at $0.3<z<1.05$, in contrast to the case for all photometrically selected galaxies for which $M_{min}$ shows significant dependence on $M_{star}$ even at low $M_{star}$. The weak stellar mass dependence is indicative of the dark halo mass being the key parameter for the formation of LRGs rather than the stellar mass. Our result suggests that the halo mass of $sim 10^{12.5 pm 0.2}h^{-1} M_{odot}$ is the critical mass for an efficient halo quenching due to the halo environment. We compare our result with the result of the hydrodynamical simulation to find that low-mass LRGs at $z sim 1$ will increase their stellar masses by an order magnitude from $z=1$ to $0$ through mergers and satellite accretions, and a large fraction of massive LRGs at $z<0.9$ consist of LRGs that are recently migrated from massive green valley galaxies or those evolved from less massive LRGs through mergers and satellite accretions.
We use three semi-analytic models (SAMs) of galaxy formation and evolution, run on the same 1$h^{-1}$Gpc MultiDark Planck2 cosmological simulation, to investigate the properties of [OII] emission line galaxies in the redshift range $0.6<z<1.2$. We compare model predictions with different observational data sets, including DEEP2--Firefly galaxies with absolute magnitudes. We estimate the [OII] luminosity, L[OII], using simple relations derived both from the models and observations and also using a public code. This code ideally uses as input instantaneous star formation rates (SFRs), which are only provided by one of the SAMs under consideration. We use this SAM to study the feasibility of inferring galaxies L[OII] for models that only provide average SFRs. We find that the post-processing computation of L[OII] from average SFRs is accurate for model galaxies with dust attenuated L[OII]$lesssim10^{42.2}$erg s$^{-1}$ ($<5%$ discrepancy). We also explore how to derive the [OII] luminosity from simple relations using global properties usually output by SAMs. Besides the SFR, the model L[OII] is best correlated with the observed-frame $u$ and $g$ broad-band magnitudes. These correlations have coefficients (r-values) above 0.64 and a dispersion that varies with L[OII]. We use these correlations and an observational one based on SFR and metallicity to derive L[OII]. These relations result in [OII] luminosity functions and halo occupation distributions with shapes that vary depending on both the model and the method used. Nevertheless, for all the considered models, the amplitude of the clustering at scales above 1$h^{-1}$Mpc remains unchanged independently of the method used to derive L[OII].
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