DTM-based Filtrations

Despite strong stability properties, the persistent homology of filtrations classically used in Topological Data Analysis, such as, e.g. the Cech or Vietoris-Rips filtrations, are very sensitive to the presence of outliers in the data from which they are computed. In this paper, we introduce and study a new family of filtrations, the DTM-filtrations, built on top of point clouds in the Euclidean space which are more robust to noise and outliers. The approach adopted in this work relies on the notion of distance-to-measure functions, and extends some previous work on the approximation of such functions.Comment: Abel Symposia, Springer, In press, Topological Data Analysi

DTM-Based Filtrations

Despite strong stability properties, the persistent homology of filtrations classically used in Topological Data Analysis, such as, e.g. the Cech or Vietoris-Rips filtrations, are very sensitive to the presence of outliers in the data from which they are computed. In this paper, we introduce and study a new family of filtrations, the DTM-filtrations, built on top of point clouds in the Euclidean space which are more robust to noise and outliers. The approach adopted in this work relies on the notion of distance-to-measure functions and extends some previous work on the approximation of such functions

Community composition and methane oxidation activity of methanotrophs associated with duckweeds in a fresh water lake

Methanotrophs are the only biological sink of the greenhouse gas methane. To understand the ecological features of methanotrophs in association with plants in the methane emitting environments, we investigated the community composition and methane oxidation of methanotrophs associated with duckweeds in a fresh water lake. Duckweeds collected from Lake Biwa, Japan over three summers showed methane consumption activity between 0.0067 and 0.89 μmol h⁻¹ g⁻¹ (wet weight), with the highest values occurring from the end of July to August. The methanotrophic community on duckweeds consisted primarily of γ-proteobacterial groups including the genera Methylomonas and Methylocaldum. Further analysis of co-cultures of a methanotroph isolate with sterilized duckweed revealed that the duckweed plant as well as the duckweed spent culture supernatant exerted an enhancing effect on methane oxidation. These results indicate that duckweeds not only provide a habitat for methanotrophs but also stimulate methanotrophic growth

JWST Measurements of Neutral Hydrogen Fractions and Ionized Bubble Sizes at z=7−12z=7-12 Obtained with Lyα\alpha Damping Wing Absorptions in 26 Bright Continuum Galaxies

We present volume-averaged neutral hydrogen fractions x_{\rm \HI} and ionized bubble radii $R_{\rm b}$ measured with Ly$\alpha$ damping wing absorptions of galaxies at the epoch of reionization. We combine JWST/NIRSpec spectra taken by CEERS, GO-1433, and DDT-2750 programs, and obtain 26 bright UV-continuum galaxies at $7<z<12$. We construct 4 composite spectra binned by redshift, and find the clear evolution of spectral flattening towards high redshift at the rest-frame $1216$ \AA\ suggesting the increase of Ly$\alpha$ damping wing absorption. We estimate Ly$\alpha$ damping wing absorption in the composite spectra with realistic templates including Ly$\alpha$ emission and circum-galactic medium absorptions. Assuming the standard inside-out reionization picture having an ionized bubble with $R_{\rm b}$ around a galaxy in the inter-galactic medium of x_{\rm \HI}, we obtain x_{\rm \HI} ($R_{\rm b}$) values monotonically increasing (decreasing) from x_{\rm \HI}={0.46}^{+0.36}_{-0.32} to ${0.83}^{+0.12}_{-0.21}$ ($R_{\rm b}={1.49}^{+0.37}_{-0.43}\times10^2$ to ${5.04}^{+8.06}_{-3.73}$ comoving Mpc) at redshift $7.140^{+0.039}_{-0.076}$ to $9.801^{+1.599}_{-1.164}$. The redshift evolution of x_{\rm \HI} indicates moderately late reionization history consistent with the one suggested from the electron scattering of cosmic microwave background and the evolution of UV luminosity function with an escape fraction $f_{\rm esc}\simeq 0.17$. Our $R_{\rm b}$ measurements are about 20 times larger than the cosmic average values estimated by analytic calculations for a given x_{\rm \HI}, while our $R_{\rm b}$ measurements are comparable with the values for merged ionized bubbles around bright galaxies predicted by recent numerical simulations

Pure Spectroscopic Constraints on UV Luminosity Functions and Cosmic Star Formation History From 25 Galaxies at zspec=8.61−13.20z_\mathrm{spec}=8.61-13.20 Confirmed with JWST/NIRSpec

We present pure spectroscopic constraints on the UV luminosity functions and cosmic star formation rate (SFR) densities from 25 galaxies at $z_\mathrm{spec}=8.61-13.20$. By reducing the JWST/NIRSpec spectra taken in multiple programs of ERO, ERS, GO, and DDT with our analysis technique, we independently confirm 16 galaxies at $z_\mathrm{spec}=8.61-11.40$ including new redshift determinations, and a bright interloper at $z_\mathrm{spec}=4.91$ that was claimed as a photometric candidate at z~16. In conjunction with nine galaxies at redshifts up to $z_\mathrm{spec}=13.20$ in the literature, we make a sample of 25 spectroscopically-confirmed galaxies in total and carefully derive the best estimates and lower limits of the UV luminosity functions. These UV luminosity function constraints are consistent with the previous photometric estimates within the uncertainties and indicate mild redshift evolution towards z~12 showing tensions with some theoretical models of rapid evolution. With these spectroscopic constraints, we obtain firm lower limits of the cosmic SFR densities and spectroscopically confirm a high SFR density at z~12 beyond the constant star-formation efficiency models, which supports earlier claims from the photometric studies. While there are no spectroscopically-confirmed galaxies with very large stellar masses violating the $\Lambda$CDM model due to the removal of the bright interloper, we confirm star-forming galaxies at $z_\mathrm{spec}=11-13$ with stellar masses much higher than model predictions. Our results indicate possibilities of high star-formation efficiency (>5%), hidden AGN, top-heavy initial mass function (possibly with Pop-III), and large scatter/variance. Having these successful and unsuccessful spectroscopy results, we suggest observational strategies for efficiently removing low redshift interlopers for future JWST programs.Comment: 27 pages, 18 figures, submitted to Ap

Statistics for Galaxy Outflows at z∼6−9z\sim 6-9 with Imaging and Spectroscopic Signatures Identified with JWST/NIRCam and NIRSpec Data

We present statistics of $z\sim 6-9$ galaxy outflows indicated by spatially-extended gas emission and broad lines. With a total of 61 spectroscopically confirmed galaxies at $z\sim 6-9$ in the JWST CEERS, GLASS, and ERO data, we find four galaxies with [O{\sc iii}]+H$\beta$ ionized gas emission significantly extended beyond the kpc-scale stellar components on the basis of the emission line images constructed by the subtraction of NIRCam broadband (line on/off-band) images. By comparison with low-$z$ galaxies, the fraction of galaxies with the spatially extended gas, 4/18, at $z\sim 6-9$ is an order of magnitude higher than those at $z\sim 0-1$, which can be explained by events triggered by frequent major mergers at high redshift. We also investigate medium- and high-resolution NIRSpec spectra of 30 galaxies at $z\sim 6-9$, and identify five galaxies with broad ($140-800$ km s$^{-1}$) lines in the [O{\sc iii}] forbidden line emission, suggestive of galaxy outflows. One galaxy at $z=6.38$ shows both the spatially-extended gas emission and the broad lines, while none of the galaxies with the spatially-extended gas emission or broad lines present a clear signature of AGN either in the line diagnostics or Type 1 AGN line broadening ($>1000$ km s$^{-1}$), which hint outflows mainly driven by stellar feedback. The existence of galaxies with/without spatially-extended gas emission or broad lines may be explained by different viewing angles towards outflows, or that these are galaxies in the early, late, post phases of galaxy outflows at high redshift, where the relatively large fractions of such galaxies indicate the longer-duration and/or more-frequent outflows at the early cosmic epoch.Comment: 16 pages, 11 figures, accepted for publication in Ap

Stellar and AGN Feedback Probed with Outflows in JWST Galaxies at z=3-9: Implications of Frequent Nearly-Spherical Galactic Fountains

We study outflows in 130 galaxies with -22<MUV<-16 at z=3-9 identified in JWST NIRSpec and NIRCam WFSS data taken by the ERO, CEERS, FRESCO, GLASS, and JADES programs. We identify 30 out of the 130 galaxies with broad components of FWHM~200-700 km/s in the emission lines of H${\alpha}$ and [OIII] that trace ionized outflows, and find no excesses from the star-formation main sequence. Four out of the 30 outflowing galaxies are Type 1 AGN whose H${\alpha}$ emission lines include line profile components as broad as FWHM>1000 km/s. With the velocity shift and line widths of the outflow broad lines, we obtain ~80-500 km/s for the outflow velocities. We find that the outflow velocities as a function of star-formation rate are comparable to or higher than those of galaxies at z~1, accounting for the selection bias, while the outflow velocities of AGN are large but not significantly different from the others. Interestingly, these outflow velocities are typically not high enough to escape from the galactic potentials, suggestive of fountain-type outflows, which are concluded on the basis of thorough comparisons with recent JWST results. We estimate mass loading factors ${\eta}$ to be 0.1-1 that are not particularly large, but comparable with those of z~1 outflows. The large fraction of galaxies with outflows (30% with high resolution data) provides constraints on outflow parameters, suggesting a wide opening angle of >45 deg and a large duty-cycle of >30%, which gives a picture of more frequent and spherical outflows in high-z galaxies.Comment: 16 pages, 11 figures, submitted to the Astrophysical Journa

A Comprehensive Study on Galaxies at z~9-17 Found in the Early JWST Data: UV Luminosity Functions and Cosmic Star-Formation History at the Pre-Reionization Epoch

We conduct a comprehensive study on dropout galaxy candidates at $z\sim 9-17$ using the first 90 arcmin$^2$ JWST/NIRCam images taken by the early release observations (ERO) and early release science (ERS) programs. With the JWST simulation images, we find that a number of foreground interlopers are selected with a weak photo-$z$ determination ($\Delta \chi^2>4$). We thus carefully apply a secure photo-$z$ selection criterion ($\Delta \chi^2>9$) and conventional color criteria with confirmations of the ERO NIRSpec spectroscopic redshifts, and obtain a total of 25 dropout galaxies at $z\sim 9-17$, including two candidates at $z_\mathrm{phot}=16.45_{-0.32}^{+0.09}$ and $16.66_{-0.34}^{+1.86}$. We perform thorough comparisons of dropout galaxies found in our work with recent JWST studies, and conclude that our galaxy sample is reliable enough for statistical analyses. We derive the UV luminosity functions at $z\sim 9-17$, and confirm that our UV luminosity functions at $z\sim 9$ and $12$ agree with those determined by previous HST and JWST studies. The cosmic star-formation rate density decreases from $z\sim 9$ to $12$, and perhaps to $17$, but the densities at $z\sim12-17$ are higher than the constant star formation efficiency model. Interestingly, there are six bright galaxy candidates at $z\sim 11-17$ with $M_{\rm UV}<-19.5$ whose stellar masses are very high, $10^{8-9} M_\odot$. Because a majority ($\sim 70\%$) of these galaxies shows no signatures of AGNs in their morphologies, the high cosmic star-formation rate densities and the existence of these stellar massive galaxies are explained by no suppression of star-formation by the UV background radiation at the pre-reionization epoch or an efficient UV radiation production by Population III-like star formation.Comment: 36 pages, 19 figures. Submitted to ApJS. Comments welcom

Lyα\alpha Emission at z=7−13z=7-13: Clear Lyα\alpha Equivalent Width Evolution Indicating the Late Cosmic Reionization History

We present the evolution of Ly$\alpha$ emission derived from 53 galaxies at $z=6.6-13.2$ that are identified by multiple JWST/NIRSpec spectroscopy programs of ERS, GO, DDT, and GTO. These galaxies fall on the star-formation main sequence and are the typical star-forming galaxies with UV magnitudes of $-22.5\leq M_\mathrm{UV}\leq-17.0$. We find that 15 out of 53 galaxies show Ly$\alpha$ emission at the $>3\sigma$ levels, and obtain Ly$\alpha$ equivalent width (EW) measurements and stringent $3\sigma$ upper limits for the 15 and 38 galaxies, respectively. Confirming that Ly$\alpha$ velocity offsets and line widths of our galaxies are comparable with those of low-redshift Ly$\alpha$ emitters, we investigate the redshift evolution of the Ly$\alpha$ EW. We find that Ly$\alpha$ EWs statistically decrease towards high redshifts on the Ly$\alpha$ EW vs. $M_{\rm UV}$ plane for various probability distributions of the uncertainties. We then evaluate neutral hydrogen fractions $x_{\rm HI}$ with the Ly$\alpha$ EW redshift evolution and the cosmic reionization simulation results on the basis of a Bayesian inference framework, and obtain $x_{\rm HI}<0.79$, $=0.62^{+0.15}_{-0.36}$, and $0.93^{+0.04}_{-0.07}$ at $z\sim7$, $8$, and $9-13$, respectively. These moderately large $x_{\rm HI}$ values are consistent with the Planck CMB optical depth measurement and previous $x_{\rm HI}$ constraints from galaxy and QSO Ly$\alpha$ damping wing absorptions, and strongly indicate a late reionization history. Such a late reionization history suggests that major sources of reionization would emerge late and be hosted by moderately massive halos in contrast with the widely-accepted picture of abundant low-mass objects for the sources of reionization.Comment: Accepted for publication in Ap

A JWST/NIRSpec First Census of Broad-Line AGNs at z=4-7: Detection of 10 Faint AGNs with M_BH~10^6-10^8 M_sun and Their Host Galaxy Properties

We present a first statistical sample of faint type-1 AGNs at $z>4$ identified by JWST/NIRSpec deep spectroscopy. Among the 185 galaxies at $z_\mathrm{spec}=3.8-8.9$ confirmed with NIRSpec, our systematic search for broad-line emission reveals 10 type-1 AGNs at $z=4.015-6.936$ whose broad component is only seen in the permitted H$\alpha$ line and not in the forbidden [OIII]$\lambda$5007 line that is detected with greater significance than H$\alpha$. The broad H$\alpha$ line widths of $\mathrm{FWHM}\simeq1000-6000\ \mathrm{km\ s^{-1}}$suggest that the AGNs have low-mass black holes with$M_\mathrm{BH}\sim10^6-10^8\ M_\odot$, remarkably lower than those of low-luminosity quasars previously identified at$z>4$with ground-based telescopes. JWST and HST high-resolution images reveal that the majority of them show extended morphologies indicating significant contribution to the total lights from their host galaxies, except for three compact objects two of which show red SEDs, probably in a transition phase from faint AGNs to low luminosity quasars. Careful AGN-host decomposition analyses show that their host's stellar masses are systematically lower than the local relation between the black hole mass and the stellar mass, implying a fast black hole growth consistent with predictions from theoretical simulations. A high fraction of the broad-line AGNs ($\sim5\%$), higher than$z\sim0$, indicates that a number density of such faint AGNs is higher than an extrapolation of the quasar luminosity function, implying a large population of AGNs including type 1 and type 2 in the early universe. Such faint AGNs contribute to cosmic reionization, while the total contribution is not large, up to$\sim50\%$at$z\sim6$, because of their faint nature.Comment: 24 pages, 16 figures, accepted for publication in Ap