分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We report the detection of a high density of redshift $z\approx 10$ galaxies behind the foreground cluster Abell 2744, selected from imaging data obtained recently with NIRCam onboard JWST by three programs -- GLASS-JWST, UNCOVER, and DDT-2756. To ensure robust estimates of the lensing magnification $\mu$, we use an improved version of our model that exploits the first epoch of NIRCam images and newly obtained MUSE spectra, and avoids regions with $\mu>5$ where the uncertainty may be higher. We detect seven bright $z\approx 10$ galaxies with demagnified rest-frame $-22 \lesssim M_{\rm UV}\lesssim -19$ mag, over an area of $\sim37$ sq. arcmin. Taking into account photometric incompleteness and the effects of lensing on luminosity and cosmological volume, we find that the density of $z\approx 10$ galaxies in the field is about $10\times$ ($3\times$) larger than the average at $M_{UV}\approx -21 (-20)$ mag reported so far. The density is even higher when considering only the GLASS-JWST data, which are the depeest and the least affected by magnification and incompleteness. The GLASS-JWST field contains 5 out of 7 galaxies, distributed along an apparent filamentary structure of 2 Mpc in projected length, and includes a close pair of candidates with $M_{\rm UV}< -20$ mag having a projected separation of only 16 kpc. These findings suggest the presence of a $z\approx 10$ overdensity in the field. In addition to providing excellent targets for efficient spectroscopic follow-up observations, our study confirms the high density of bright galaxies observed in early JWST observations, but calls for multiple surveys along independent lines of sight to achieve an unbiased estimate of their average density and a first estimate of their clustering.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: The recent rapid growth of the black hole (BH) catalog from gravitational waves (GWs), has allowed us to study the substructure of black hole mass function (BHMF) beyond the simplest Power-Law distribution. However, the BH masses inferred from binary BH merger events, may be systematically 'brightened' or 'dimmed' by the gravitational lensing effect. In this work, we investigate the impact of gravitational lensing on the BHMF inference considering the detection of the third-generation GW detector -- the Einstein Telescope (ET). We focus on high redshift, $z=10$, in order to obtain the upper limits of this effect. We use Monte Carlo (MC) method to simulate the data adopting 3 original BHMFs under Un-Lensed and Lensed scenarios, then recover the parameters of BHMFs from the mock data, and compare the difference of results, respectively. We found that all the parameters are well recovered within one standard deviation(std., 1$\sigma$), and all 3 BHMF models are reconstructed within 68\% credible interval, suggesting that lensing would not change the main structure drastically, even at very high redshifts and with high precision of ET. And the modest influence beyond $50M_{\odot}$, depends on the modeling of the high mass tail or substructure of BHMF. We conclude that the impact of lensing on BHMF inference with ET can be safely ignored in the foreseeable future. Careful handling of lensing effects is required only when focusing on an accurate estimation of the high mass end of BHMF at high redshifts.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We present the results of a first search for galaxy candidates at z$\sim$9--15 on deep seven-bands NIRCam imaging acquired as part of the GLASS-JWST Early Release Science Program on a flanking field of the Frontier Fields cluster A2744. Candidates are selected via two different renditions of the Lyman-break technique, isolating objects at z$\sim$9-11, and z$\sim$9-15, respectively, supplemented by photometric redshifts obtained with two independent codes. We find five color-selected candidates at z$>$9, plus one additional candidate with photometric redshift z$_{phot}\geq$9. In particular, we identify two bright candidates at $M_{UV}\simeq -21$ that are unambiguously placed at $z\simeq 10.6$ and $z\simeq 12.2$, respectively. The total number of galaxies discovered at $z>9$ is in line with the predictions of a non-evolving LF. The two bright ones at $z>10$ are unexpected given the survey volume, although cosmic variance and small number statistics limits general conclusions. This first search demonstrates the unique power of JWST to discover galaxies at the high redshift frontier. The candidates are ideal targets for spectroscopic follow-up in Cycle$-2$.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: Given their extremely faint apparent brightness, the nature of the first galaxies and how they reionized the Universe's gas are not yet understood. Here we report the discovery, in JWST imaging, of a highly magnified, low mass (log(Mstellar/Msun) = 7.63+0.22-0.24) galaxy visible when the Universe was only 510 Myr old, and follow-up JWST spectroscopy from Lyman alpha to [O III] 5007 A in its rest frame. We detect the [O III] 5007 A and H Beta emission lines with a respective signal-to-noies ratio of 40 and 7, and five additional lines with signal-to-noise greater than 3. The galaxy's magnification of approximately 20 allows us to measure a radius of 16.4+10.7-7.0 pc, which is a factor of 9.3+10.5-4.4 (3.5 sigma) smaller than galaxies with comparable luminosity at z = 6 - 8.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: JWST observations confirm the existence of galaxies as early as 300Myr and at a higher number density than expected based on galaxy formation models and HST observations. Yet, sources confirmed spectroscopically in the first 500Myr have estimated stellar masses $8$, we identify evidence of absorption lines (Si, C and Fe), with low confidence individual detections but SNR$>6$ when stacked. The absorption features suggest that Ly$\alpha$ is damped by the interstellar and circumgalactic medium. Our observations provide evidence of rapid efficient build-up of mass and metals in the immediate aftermath of the Big Bang through mergers, demonstrating that massive galaxies with several billion stars exist earlier than expected.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We present the reduced images and multi-wavelength catalog of the first JWST NIRCam extra-galactic observations from the GLASS Early Release Science Program, obtained as coordinated parallels of the NIRISS observations of the Abell 2744 cluster. Images in seven bands (F090W, F115W, F150W, F200W, F277W, F356W, F444W) have been reduced using an augmented version of the official JWST pipeline; we discuss the procedures adopted to remove or mitigate defects in the raw images. We obtain a multi--band catalog by means of forced aperture photometry on PSF-matched images at the position of F444W-detected sources. The catalog is intended to enable early scientific investigations, and it is optimized for faint galaxies; it contains 6368 sources, with limiting magnitude 29.7 at 5$\sigma$ in F444W. We release both images and catalog in order to allow the community to familiarize with the JWST NIRCam data and evaluate their merit and limitations given the current level of knowledge of the instrument.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: Strong lensing of gravitational waves (GWs) is attracting growing attention of the community. The event rates of lensed GWs by galaxies were predicted in numerous papers, which used some approximations to evaluate the GW strains detectable by a single detector. The joint-detection of GW signals by a network of instruments will increase the detecting ability of fainter and farther GW signals, which could increase the detection rate of the lensed GWs, especially for the 3rd generation detectors, e.g., Einstein Telescope (ET) and Cosmic Explorer (CE). Moreover, realistic GW templates will improve the accuracy of the prediction. In this work, we consider the detection of galaxy-scale lensed GW events under the 2nd, 2.5th, and 3rd generation detectors with the network scenarios and adopt the realistic templates to simulate GW signals. Our forecast is based on the Monte Carlo technique which enables us to take Earth's rotation into consideration. We find that the overall detection rate is improved, especially for the 3rd generation detector scenarios. More precisely, it increases by ~37% adopting realistic templates, and under network detection strategy, further increases by ~58% comparing with adoption of the realistic templates, and we estimate that the 3rd generation GW detectors will detect hundreds lensed events per year. The effect from the Earth's rotation is weakened in the detector network strategy.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: The recent rapid growth of the black hole (BH) catalog from gravitational waves (GWs), has allowed us to study the substructure of black hole mass function (BHMF) beyond the simplest Power-Law distribution. However, the BH masses inferred from binary BH merger events, may be systematically 'brightened' or 'dimmed' by the gravitational lensing effect. In this work, we investigate the impact of gravitational lensing on the BHMF inference considering the detection of the third-generation GW detector -- the Einstein Telescope (ET). We focus on high redshift, $z=10$, in order to obtain the upper limits of this effect. We use Monte Carlo (MC) method to simulate the data adopting 3 original BHMFs under Un-Lensed and Lensed scenarios, then recover the parameters of BHMFs from the mock data, and compare the difference of results, respectively. We found that all the parameters are well recovered within one standard deviation(std., 1$\sigma$), and all 3 BHMF models are reconstructed within 68\% credible interval, suggesting that lensing would not change the main structure drastically, even at very high redshifts and with high precision of ET. And the modest influence beyond $50M_{\odot}$, depends on the modeling of the high mass tail or substructure of BHMF. We conclude that the impact of lensing on BHMF inference with ET can be safely ignored in the foreseeable future. Careful handling of lensing effects is required only when focusing on an accurate estimation of the high mass end of BHMF at high redshifts.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We present the first rest-frame optical size-luminosity relation of galaxies at $z>7$, using the NIRCam imaging data obtained by the GLASS James Webb Space Telescope Early Release Science (GLASS-JWST-ERS) program, providing the deepest extragalactic data of the ERS campaign. Our sample consist of 19 photometrically selected bright galaxies with $m_\text{F444W}\leq27.8$ at $77$. Given the limited sample size and magnitude range, we first fix the slope to that observed for larger samples in rest-frame UV using HST samples. The median size $r_0$ at the reference luminosity $M=-21$ decreases slightly from rest-frame optical ($600\pm80$ pc) to UV ($450\pm130$ pc). We then re-fit the size-luminosity relation allowing the slope to vary. The slope is consistent with $\beta\sim0.2$ for all bands except F150W, where we find a marginally steeper slope of $\beta=0.53\pm0.15$. The steep UV slope is mainly driven by the smallest and faintest galaxies. If confirmed by larger samples, it implies that the UV size-luminosity relation breaks toward the faint end as suggested by lensing studies.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We report the discovery of an extremely magnified star at redshift $z=2.65$ in James Webb Space Telescope (JWST) NIRISS pre-imaging of the Abell 2744 galaxy-cluster field. The star's background host galaxy lies on a fold caustic of the foreground lens, and the cluster creates a pair of images of the region close to the lensed star. We identified the bright transient in one of the merging images at a distance of $\sim 0.15"$ from the critical curve, by subtracting the JWST F115W and F150W imaging from coadditions of archival Hubble Space Telescope (HST) F105W and F125W images and F140W and F160W images, respectively. Since the time delay between the two images should be only hours, the transient must be the microlensing event of an individual star, as opposed to a luminous stellar explosion which would persist for days to months. Analysis of individual exposures suggests that the star's magnification is not changing rapidly during the observations. From photometry of the point source through the F115W, F150W, and F200W filters, we identify a strong Balmer break, and modeling allows us to constrain the star's temperature to be approximately 7,000--12,000 K.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We present the survey design, implementation, and outlook for COSMOS-Web, a 255 hour treasury program conducted by the James Webb Space Telescope in its first cycle of observations. COSMOS-Web is a contiguous 0.54 deg$^2$ NIRCam imaging survey in four filters (F115W, F150W, F277W, and F444W) that will reach 5$\sigma$ point source depths ranging $\sim$27.5-28.2 magnitudes. In parallel, we will obtain 0.19 deg$^2$ of MIRI imaging in one filter (F770W) reaching 5$\sigma$ point source depths of $\sim$25.3-26.0 magnitudes. COSMOS-Web will build on the rich heritage of multiwavelength observations and data products available in the COSMOS field. The design of COSMOS-Web is motivated by three primary science goals: (1) to discover thousands of galaxies in the Epoch of Reionization ($64$ and place constraints on the formation of the Universe's most massive galaxies ($M_\star>10^{10}$\,M$_\odot$), and (3) directly measure the evolution of the stellar mass to halo mass relation using weak gravitational lensing out to $z\sim2.5$ and measure its variance with galaxies' star formation histories and morphologies. In addition, we anticipate COSMOS-Web's legacy value to reach far beyond these scientific goals, touching many other areas of astrophysics, such as the identification of the first direct collapse black hole candidates, ultracool sub-dwarf stars in the Galactic halo, and possibly the identification of $z>10$ pair-instability supernovae. In this paper we provide an overview of the survey's key measurements, specifications, goals, and prospects for new discovery.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We present images and a multi-wavelength photometric catalog based on all of the JWST NIRCam observations obtained to date in the region of the Abell 2744 galaxy cluster. These data come from three different programs, namely the GLASS-JWST Early Release Science Program, UNCOVER, and Director's Discretionary Time program 2756. The observed area in the NIRCam wide-band filters - covering the central and extended regions of the cluster, as well as new parallel fields - is 46.5 arcmin$^2$ in total. All images in eight bands (F090W, F115W, F150W, F200W, F277W, F356W, F410M, F444W) have been reduced adopting the latest calibration and references available to date. Data reduction has been performed using an augmented version of the official JWST pipeline, with improvements aimed at removing or mitigating defects in the raw images and improve the background subtraction and photometric accuracy. We obtain a F444W-detected multi-band catalog including all NIRCam data and available HST data, adopting forced aperture photometry on PSF-matched images. The catalog is intended to enable early scientific investigations, and is optimized for the study of faint galaxies; it contains 24389 sources, with a 5$\sigma$ limiting magnitude in the F444W band ranging from 28.5 to 30.5 AB, as a result of the varying exposure times of the surveys that observed the field. We publicly release the reduced NIRCam images, associated multi-wavelength catalog, and code adopted for $1/f$ noise removal with tha aim of aiding users to familiarize themselves with JWST NIRCam data and identify targets for follow-up observations.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We report the first gas-phase metallicity map of a distant galaxy measured with the James Webb Space Telescope (JWST). We use the NIRISS slitless spectroscopy acquired by the GLASS Early Release Science program to spatially resolve the rest-frame optical nebular emission lines in a gravitationally lensed galaxy at $z=3.06$ behind the Abell 2744 galaxy cluster. This galaxy (dubbed GLASS-Zgrad1) has stellar mass $\sim10^{8.6} M_\odot$, instantaneous star formation rate $\sim8.6$ $M_\odot$/yr (both corrected for lensing magnification), and global metallicity one-fourth solar. From its emission line maps ([O III], H$\beta$, H$\gamma$, [Ne III], and [O II]) we derive its spatial distribution of gas-phase metallicity using a well-established forward-modeling Bayesian inference method. The exquisite resolution and sensitivity of JWST/NIRISS, combined with lensing magnification, enable us to resolve this $z\sim3$ dwarf galaxy in $\gtrsim$50 resolution elements with sufficient signal, an analysis hitherto not possible. We find that the radial metallicity gradient of GLASS-Zgrad1 is strongly inverted (i.e. positive): $\Delta\log({\rm O/H})/\Delta r$ = $0.165\pm0.023$ $\mathrm{dex~kpc^{-1}}$. This inverted gradient may be due to tidal torques induced by a massive nearby ($\sim$15 kpc projected) galaxy, which can cause inflows of metal-poor gas into the central regions of GLASS-Zgrad1. These first results showcase the power of JWST wide-field slitless spectroscopic modes to resolve the mass assembly and chemical enrichment of low-mass galaxies in and beyond the peak epoch of cosmic star formation ($z\gtrsim2$). Reaching masses $\lesssim 10^9~M_\odot$ at these redshifts is especially valuable to constrain the effects of galactic feedback and environment, and is possible only with JWST's new capabilities.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: Strongly lensed explosive transients such as supernovae, gamma-ray bursts, fast radio bursts, and gravitational waves are very promising tools to determine the Hubble constant ($H_0$) in the near future in addition to strongly lensed quasars. In this work, we show that the transient nature of the point source provides an advantage over quasars: the lensed host galaxy can be observed before or after the transient's appearance. Therefore, the lens model can be derived from images free of contamination from bright point sources. We quantify this advantage by comparing the precision of a lens model obtained from the same lenses with and without point sources. Based on Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) observations with the same sets of lensing parameters, we simulate realistic mock datasets of 48 quasar lensing systems (i.e., adding AGN in the galaxy center) and 48 galaxy-galaxy lensing systems (assuming the transient source is not visible but the time delay and image positions have been or will be measured). We then model the images and compare the inferences of the lens model parameters and $H_0$. We find that the precision of the lens models (in terms of the deflector mass slope) is better by a factor of 4.1 for the sample without lensed point sources, resulting in an increase of $H_0$ precision by a factor of 2.9. The opportunity to observe the lens systems without the transient point sources provides an additional advantage for time-delay cosmography over lensed quasars. It facilitates the determination of higher signal-to-noise stellar kinematics of the main deflector, and thus its mass density profile, which in turn plays a key role in breaking the mass-sheet degeneracy and constraining $H_0$.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We measure the size-luminosity relation of photometrically-selected galaxies within the redshift range $z\sim6-9$, using galaxies lensed by six foreground Hubble Frontier Fields (HFF) clusters. The power afforded by strong gravitational lensing allows us to observe fainter and smaller galaxies than in blank fields. We select our sample of galaxies and obtain their properties, e.g., redshift, magnitude, from the photometrically-derived ASTRODEEP catalogues. The intrinsic size is measured with the Lenstruction software, and completeness maps are created as a function of size and luminosity via the GLACiAR2 software. We perform a Bayesian analysis to estimate the intrinsic and incompleteness-corrected size-luminosity distribution, with parameterization $r_e \propto L^\beta$. We find slopes of $\beta\sim0.48\pm0.08$ at $z\sim6-7$ and $\beta\sim0.68\pm0.14$ at $z\sim8.5$, adopting the Bradac lens model. The slope derived by lensed galaxies is steeper than that obtained in blank fields and is consistent with other independent determinations of the size-luminosity relation from the HFF dataset. We also investigate the systematic uncertainties correlated with the choice of lens models, finding that the slopes of size-luminosity relations derived from different models are consistent with each other, i.e. the modeling errors are not a significant source of uncertainty in the size-luminosity relation.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: The appearance of galaxies over the first billion years after the Big Bang is believed to be responsible for the last dramatic change in the state of the Universe. Ultraviolet photons from galaxies within this time period - the Epoch of Reionization - ionized intergalactic Hydrogen, rendering the Universe transparent to UV radiation and ending the so-called cosmic Dark Ages, sometime after redshift $z\sim8$. The majority of ionizing photons in the first few hundred Myrs of cosmic history are thought to derive from galaxies significantly fainter than the characteristic luminosity $L^{*}$. These faint galaxies are thought to be surrounded by sufficient neutral gas to prevent the escape of the Lyman-$\alpha$ photons that would allow confirmation with current observatories. Here we demonstrate the power of the recently commissioned James Webb Space Telescope to transform our understanding of the sources of reionization, by reporting the first spectroscopic confirmation of a very low luminosity ($\sim0.05 L^{*}$) galaxy at $z=9.76$, observed 480 Myr after the Big Bang, via the detection of the Lyman-break and redward continuum with the NIRSpec and NIRCam instruments. The galaxy JD1 is gravitationally magnified by a factor of $\mu\sim13$ by the foreground cluster A2744. The power of JWST and lensing allows us to peer deeper than ever before into the cosmic Dark Ages, revealing the compact ($\sim$150 pc) and complex morphology and physical properties of an ultrafaint galaxy ($M_{\rm UV}=-17.45$).
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We report the first gas-phase metallicity map of a distant galaxy measured with the James Webb Space Telescope (JWST). We use the NIRISS slitless spectroscopy acquired by the GLASS Early Release Science program to spatially resolve the rest-frame optical nebular emission lines in a gravitationally lensed galaxy at $z=3.06$ behind the Abell 2744 galaxy cluster. This galaxy (dubbed GLASS-Zgrad1) has stellar mass $\sim10^{8.6} M_\odot$, instantaneous star formation rate $\sim8.6$ $M_\odot$/yr (both corrected for lensing magnification), and global metallicity one-fourth solar. From its emission line maps ([O III], H$\beta$, H$\gamma$, [Ne III], and [O II]) we derive its spatial distribution of gas-phase metallicity using a well-established forward-modeling Bayesian inference method. The exquisite resolution and sensitivity of JWST/NIRISS, combined with lensing magnification, enable us to resolve this $z\sim3$ dwarf galaxy in $\gtrsim$50 resolution elements with sufficient signal, an analysis hitherto not possible. We find that the radial metallicity gradient of GLASS-Zgrad1 is strongly inverted (i.e. positive): $\Delta\log({\rm O/H})/\Delta r$ = $0.165\pm0.023$ $\mathrm{dex~kpc^{-1}}$. This inverted gradient may be due to tidal torques induced by a massive nearby ($\sim$15 kpc projected) galaxy, which can cause inflows of metal-poor gas into the central regions of GLASS-Zgrad1. These first results showcase the power of JWST wide-field slitless spectroscopic modes to resolve the mass assembly and chemical enrichment of low-mass galaxies in and beyond the peak epoch of cosmic star formation ($z\gtrsim2$). Reaching masses $\lesssim 10^9~M_\odot$ at these redshifts is especially valuable to constrain the effects of galactic feedback and environment, and is possible only with JWST's new capabilities.