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Register a new userThe Subaru HSC Galaxy Clustering with Photometric Redshift I: Dark Halo Masses Versus Baryonic Properties of Galaxies at 0.3<z<1.4
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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.
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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.
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 investigate the clustering properties of Lyman-break galaxies (LBGs) at $zsim6$ - $8$. Using the semi-analytical model {scshape Meraxes} constructed as part of the Dark-ages Reionization And Galaxy-formation Observables from Numerical Simulation (DRAGONS) project, we predict the angular correlation function (ACF) of LBGs at $zsim6$ - $8$. Overall, we find that the predicted ACFs are in good agreement with recent measurements at $zsim 6$ and $zsim 7.2$ from observations consisting of the Hubble eXtreme Deep Field (XDF), the Hubble Ultra-Deep Field (HUDF) and Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) field. We confirm the dependence of clustering on luminosity, with more massive dark matter haloes hosting brighter galaxies, remains valid at high redshift. The predicted galaxy bias at fixed luminosity is found to increase with redshift, in agreement with observations. We find that LBGs of magnitude $M_{{rm AB(1600)}} < -19.4$ at $6lesssim z lesssim 8$ reside in dark matter haloes of mean mass $sim 10^{11.0}$- $10^{11.5} M_{rm odot}$, and this dark matter halo mass does not evolve significantly during reionisation.
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 conducted observations of 12CO(J=5-4) and dust thermal continuum emission toward twenty star-forming galaxies on the main sequence at z~1.4 using ALMA to investigate the properties of the interstellar medium. The sample galaxies are chosen to trace the distributions of star-forming galaxies in diagrams of stellar mass-star formation rate and stellar mass-metallicity. We detected CO emission lines from eleven galaxies. The molecular gas mass is derived by adopting a metallicity-dependent CO-to-H2 conversion factor and assuming a CO(5-4)/CO(1-0) luminosity ratio of 0.23. Molecular gas masses and its fractions (molecular gas mass/(molecular gas mass + stellar mass)) for the detected galaxies are in the ranges of (3.9-12) x 10^{10} Msun and 0.25-0.94, respectively; these values are significantly larger than those in local spiral galaxies. The molecular gas mass fraction decreases with increasing stellar mass; the relation holds for four times lower stellar mass than that covered in previous studies, and that the molecular gas mass fraction decreases with increasing metallicity. Stacking analyses also show the same trends. The dust thermal emissions were clearly detected from two galaxies and marginally detected from five galaxies. Dust masses of the detected galaxies are (3.9-38) x 10^{7} Msun. We derived gas-to-dust ratios and found they are 3-4 times larger than those in local galaxies. The depletion times of molecular gas for the detected galaxies are (1.4-36) x 10^{8} yr while the results of the stacking analysis show ~3 x 10^{8} yr. The depletion time tends to decrease with increasing stellar mass and metallicity though the trend is not so significant, which contrasts with the trends in local galaxies.
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