Test for anisotropy in the mean of the CMB temperature fluctuation in spherical harmonic space

The standard models of inflation predict statistically homogeneous and isotropic primordial fluc- tuations, which should be tested by observations. In this paper we test the statistical isotropy of the mean of the CMB temperature fluctuations measured by the WMAP in the spherical harmonic space. A classical method to test a mean, like the simple student's-t test, is not appropriate for this purpose because the WMAP data contain anisotropic instrumental noise and suffer from the effect of the mask for the foreground emissions which breaks the statistical independence. Here we perform a band-power analysis with Monte-Carlo simulations in which we take into account the anisotropic noise and the mask. We find evidence of a non-zero mean at 99.93 % confidence level in a particular range of multipoles. The evidence against the zero-mean assumption as a whole is still significant at the 99 % confidence level even if the fact is taken into account that we have tested multiple ranges.Comment: 7 pages, 6 figures, and 2 tables, submitted to PRD, comments welcom

Galaxy-dark matter connection of photometric galaxies from the HSC-SSP Survey: Galaxy-galaxy lensing and the halo model

We infer the connection between the stellar mass of galaxies from the Subaru Hyper Suprime-Cam (HSC) survey, and their dark matter halo masses and its evolution in two bins of redshifts between $[0.3, 0.8]$. We use the measurements of the weak lensing signal of galaxies using background sources from the Year 1 shape catalog from the HSC survey. We bin galaxies in stellar mass with varying thresholds ranging from $8.6 \leq \log [ M_*/(h^{-2} {M_\odot})] \leq 11.2$ and use stringent cuts in the selection of source galaxies to measure the weak lensing signal. We model these measurements of the weak lensing signal together with the abundance of galaxies in the halo occupation distribution framework. We obtain constraints on the halo occupation parameters of central galaxies $M_{\rm min}$ and $\sigma_{\log M}$, which correspond to the halo mass at which central galaxies for each threshold sample reach half occupancy, and its scatter, respectively, along with parameters that describe the occupation of the satellite galaxies. The measurements of abundance and weak lensing individually constrain different degeneracy directions in the $M_{\rm min}$ and $\sigma_{\log M}$ plane, thus breaking the degeneracy in these parameters. We demonstrate that the weak lensing measurements are best able to constrain the average central halo masses, $\langle M_{\rm cen} \rangle$. We compare our measurements to those obtained using the abundance and clustering of these galaxies as well as the subhalo abundance matching measurements and demonstrate qualitative agreement. We find that the galaxy-dark matter connection does not vary significantly between redshift bins we explore in this study. Uncertainties in the photometric redshift of the lens galaxies imply that more efforts are required to understand the true underlying stellar mass-halo mass relation of galaxies and its evolution over cosmic epoch

Galaxy Manifold: Characterizing and understanding galaxies with two parameters

We report the discovery of a two-dimensional Galaxy Manifold within the multi-dimensional luminosity space of local galaxies. The multi-dimensional luminosity space is constructed using 11 bands that span from far ultraviolet to near-infrared for redshift < 0.1 galaxies observed with GALEX, SDSS, and UKIDSS. The two latent parameters are sufficient to express 93.2% of the variance in the galaxy sample, suggesting that this Galaxy Manifold is one of the most efficient representations of galaxies. The transformation between the observed luminosities and the manifold parameters as an analytic mapping is provided. The manifold representation provides accurate (85%) morphological classifications with a simple linear boundary, and galaxy properties can be estimated with minimal scatter (0.12 dex and 0.04 dex for star formation rate and stellar mass, respectively) by calibrating with the two-dimensional manifold location. Under the assumption that the manifold expresses the possible parameter space of galaxies, the evolution on the manifold is considered. We find that constant and exponentially decreasing star formation histories form almost orthogonal modes of evolution on the manifold. Through these simple models, we understand that the two modes are closely related to gas content, which suggests the close relationship of the manifold to gas accretion. Without assuming a star formation history, a gas-regulated model reproduces an exponentially declining star formation history with a timescale of $\sim$1.2 Gyrs on the manifold. Lastly, the found manifold suggests a paradigm where galaxies are characterized by their mass/scale and specific SFR, which agrees with previous studies of dimensionality reduction.Comment: Submitted to MNRAS. 15 pages and 17 figures. All comments are welcom

Compact [C II] emitters around a C IV absorption complex at redshift 5.7

The physical conditions of the circumgalactic medium are probed by intervening absorption-line systems in the spectrum of background quasi-stellar objects out to the epoch of cosmic reionization. A correlation between the ionization state of the absorbing gas and the nature of the nearby galaxies has been suggested by the sources detected either in Lyalpha or [C ii] 158 m near to respectively highly-ionized and neutral absorbers. This is also likely linked to the global changes in the incidence of absorption systems of different types and the process of cosmic reionization. Here we report the detection of two [C ii]-emitting galaxies at redshift $z \sim 5.7$ that are associated with a complex high-ionization C iv absorption system. These objects are part of an overdensity of galaxies and have compact sizes (< 2.4 kpc) and narrow line widths (FWHM $\sim$ 62--64 km s-1). Hydrodynamic simulations predict that similar narrow [C ii] emission may arise from the heating of small ($\lesssim$ 3 kpc) clumps of cold neutral medium or a compact photodissociation region. The lack of counterparts in the rest-frame ultraviolet indicates severe obscuration of the sources that are exciting the [C ii] emission. These results may suggest a connection between the properties of the [C ii] emission, the rare overdensity of galaxies and the unusual high ionization state of the gas in this region.Comment: Published in Nature on 10 May 2023; authors' version; link to the paper: https://www.nature.com/articles/s41586-023-05901-

EIGER I. a large sample of [OIII]-emitting galaxies at 5.3<z<6.95.3 < z < 6.9 and direct evidence for local reionization by galaxies

We present a first sample of 117 [OIII]$\lambda\lambda$4960,5008-selected star-forming galaxies at $5.33 < z < 6.93$ detected in JWST/NIRCam 3.5$\mu$m slitless spectroscopy of a $6.5 \times 3.4$ arcmin$^2$ field centered on the hyperluminous quasar SDSS J0100+2802, obtained as part of the EIGER (Emission-line galaxies and Intergalactic Gas in the Epoch of Reionization) survey. Three prominent galaxy overdensities are observed, one of them at the redshift of the quasar. Galaxies are found within 200 pkpc and 105 km s$^{-1}$ of four known metal absorption-line systems in this redshift range. We focus on the role of the galaxies in ionizing the surrounding intergalactic medium (IGM) during the later stages of cosmic reionization and construct the mean Ly$\alpha$ and Ly$\beta$ transmission as a function of distance from the galaxies. At the lowest redshifts in our study, $5.3 < z < 5.7$, the IGM transmission rises monotonically with distance from the galaxies. This is as expected when galaxies reside at peaks in the overdensity field of an IGM that is ionized by more or less uniform ionizing background, and has been seen at lower redshifts. In contrast, at $5.7 < z < 6.14$, the transmission of both Ly$\alpha$ and Ly$\beta$ first increases with distance, but then peaks at a distance of 5 cMpc before declining. This peak in transmission is qualitatively similar to that seen (albeit at smaller distances and higher redshifts) in the THESAN simulations. Finally, in the region $6.15 < z < 6.26$ where the additional ionizing radiation from the quasar dominates, the monotonic increase in transmission with distance is re-established. This result is interpreted to represent evidence that the transmission of the IGM at $z \sim 5.9$ towards J0100+2802 results from the ``local'' ionizing radiation of galaxies that dominates over the much reduced cosmic background.Comment: 24 pages, 14 figures, submitted to ApJ, comments welcom

EIGER II. first spectroscopic characterisation of the young stars and ionised gas associated with strong Hβ\beta and [OIII] line-emission in galaxies at z=5-7 with JWST

We present emission-line measurements and physical interpretations for a sample of 117 [OIII] emitting galaxies at $z=5.33-6.93$, using the first deep JWST/NIRCam wide field slitless spectroscopic observations. Our 9.7-hour integration is centered upon the $z=6.3$ quasar J0100+2802 -- the first of six fields targeted by the EIGER survey -- and covers $\lambda=3-4$ microns. We detect 133 [OIII] doublets, but merge pairs within $\approx$10 kpc and 600 km s$^{-1}$, motivated by their small scale clustering excess. We detect H$\beta$ in 68 and H$\gamma$ emission in two galaxies. The galaxies are characterised by a UV luminosity M$_{\rm UV}\sim-19.6$ ($-17.7$ to $-22.3$), stellar mass ~$10^8$ $(10^{6.8-10.1})$ M$_{\odot}$, H$\beta$ and [OIII] EWs $\approx$ 850 Angstrom (up to 3000 Angstrom), young ages (~100 Myr), a highly excited interstellar medium ([OIII]/H$\beta\approx6$) and low dust attenuations. These high EWs are very rare in the local Universe, but we show they are ubiquitous at $z\sim6$ based on the measured number densities. The stacked spectrum reveals H$\gamma$ and [OIII]$_{4364}$ which shows that the galaxies are typically dust and metal poor (E(B-V)=0.1, 12+log(O/H)=7.4) with a high electron temperature ($2\times10^4$ K) and a production efficiency of ionising photons ($\xi_{\rm ion}=10^{25.3}$ Hz erg$^{-1}$). We further show the existence of a strong mass-metallicity relation. The young highly ionising stellar populations, moderately low metallicities, low dust attenuations and high ionisation state in z~6 galaxies conspire to maximise the [OIII] output from galaxies, yielding an [OIII] luminosity density at z~6 that is significantly higher than at z~2, despite the order of magnitude decline in cosmic star formation. Thus, [OIII] emission-line surveys with JWST prove a highly efficient method to trace the galaxy density in the epoch of reionization.Comment: Accepted for publication in ApJ. Main text 22 pages, 20 figures. Main results in Figs 14 (Xi_ion), 15 (MEx diagram),17 (MZR), 19 ([OIII] luminosity density