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Register a new userSimulating JWST deep extragalactic imaging surveys and physical parameter recovery
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We present a new prospective analysis of deep multi-band imaging with the James Webb Space Telescope (JWST). In this work, we investigate the recovery of high-redshift $5<z<12$ galaxies through extensive image simulations of accepted JWST programs such as CEERS in the EGS field and HUDF GTO. We introduce complete samples of $sim300,000$ galaxies with stellar masses $log(M_*/M_odot)>6$ and redshifts $0<z<15$, as well as galactic stars, into realistic mock NIRCam, MIRI and HST images to properly describe the impact of source blending. We extract the photometry of the detected sources as in real images and estimate the physical properties of galaxies through spectral energy distribution fitting. We find that the photometric redshifts are primarily limited by the availability of blue-band and near-infrared medium-band imaging. The stellar masses and star-formation rates are recovered within $0.25$ and $0.3$ dex respectively, for galaxies with accurate photometric redshifts. Brown dwarfs contaminating the $z>5$ galaxy samples can be reduced to $<0.01$ arcmin$^{-2}$ with a limited impact on galaxy completeness. We investigate multiple high-redshift galaxy selection techniques and find the best compromise between completeness and purity at $5<z<10$ using the full redshift posterior probability distributions. In the EGS field, the galaxy completeness remains higher than $50%$ for $m_text{UV}<27.5$ sources at all redshifts, and the purity is maintained above $80$ and $60%$ at $zleq7$ and $10$ respectively. The faint-end slope of the galaxy UV luminosity function is recovered with a precision of $0.1-0.25$, and the cosmic star-formation rate density within $0.1$ dex. We argue in favor of additional observing programs covering larger areas to better constrain the bright end.
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The JWST MIRI instrument will revolutionize extragalactic astronomy with unprecedented sensitivity and angular resolution in mid-IR. Here, we assess the potential of MIRI photometry to constrain galaxy properties in the Cosmic Evolution Early Release Science (CEERS) survey. We derive estimated MIRI fluxes from the spectral energy distributions (SEDs) of real sources that fall in a planned MIRI pointing. We also obtain MIRI fluxes for hypothetical AGN-galaxy mixed models varying the AGN fractional contribution to the total IR luminosity ($rm frac_{AGN}$). Based on these model fluxes, we simulate CEERS imaging (3.6-hour exposure) in 6 bands from F770W to F2100W using MIRISIM, and reduce these data using JWST PIPELINE. We perform PSF-matched photometry with TPHOT, and fit the source SEDs with X-CIGALE, simultaneously modeling photometric redshift and other physical properties. Adding the MIRI data, the accuracy of both redshift and $rm frac_{AGN}$ is generally improved by factors of $gtrsim 2$ for all sources at $zlesssim 3$. Notably, for pure-galaxy inputs ($rm frac_{AGN}=0$), the accuracy of $rm frac_{AGN}$ is improved by $sim 100$ times thanks to MIRI. The simulated CEERS MIRI data are slightly more sensitive to AGN detections than the deepest X-ray survey, based on the empirical $L_{rm X}$-$L_{rm 6mu m}$ relation. Like X-ray observations, MIRI can also be used to constrain the AGN accretion power (accuracy $approx 0.3$ dex). Our work demonstrates that MIRI will be able to place strong constraints on the mid-IR luminosities from star formation and AGN, and thereby facilitate studies of the galaxy/AGN co-evolution.
We present predictions for the outcome of deep galaxy surveys with the $James$ $Webb$ $Space$ $Telescope$ ($JWST$) obtained from a physical model of galaxy formation in $Lambda$CDM. We use the latest version of the GALFORM model, embedded within a new ($800$ Mpc)$^{3}$ dark matter only simulation with a halo mass resolution of $M_{rm halo}>2times10^{9}$ $h^{-1}$ M$_{odot}$. For computing full UV-to-mm galaxy spectral energy distributions, including the absorption and emission of radiation by dust, we use the spectrophotometric radiative transfer code GRASIL. The model is calibrated to reproduce a broad range of observational data at $zlesssim6$, and we show here that it can also predict evolution of the rest-frame far-UV luminosity function for $7lesssim zlesssim10$ which is in good agreement with observations. We make predictions for the evolution of the luminosity function from $z=16$ to $z=0$ in all broadband filters on the Near InfraRed Camera (NIRCam) and Mid InfraRed Instrument (MIRI) on $JWST$ and present the resulting galaxy number counts and redshift distributions. Our fiducial model predicts that $sim1$ galaxy per field of view will be observable at $zsim11$ for a $10^4$ s exposure with NIRCam. A variant model, which produces a higher redshift of reionization in better agreement with $Planck$ data, predicts number densities of observable galaxies $sim5times$ greater at this redshift. Similar observations with MIRI are predicted not to detect any galaxies at $zgtrsim6$. We also make predictions for the effect of different exposure times on the redshift distributions of galaxies observable with $JWST$, and for the angular sizes of galaxies in $JWST$ bands.
Since the IAU (maser-)Symposium 287 in Stellenbosch/South Africa (Jan. 2012), great progress has been achieved in studying extragalactic maser sources. Sensitivity has reached a level allowing for dedicated maser surveys of extragalactic objects. These included, during the last years, water vapor (H2O), methanol (CH3OH), and formaldehyde (H2CO), while surveys related to hydroxyl (OH), cyanoacetylene (HC3N) and ammonia (NH3) may soon become (again) relevant. Overall, with the upgraded Very Large Array (VLA), the Atacama Large Millimeter/submillimeter Array (ALMA), FAST (Five hundred meter Aperture Synthesis Telescope) and the low frequency arrays APERTIF (APERture Tile in Focus), ASKAP (Australian Square Kilometer Array Pathfinder) and MeerKAT (Meer Karoo Array Telescope), extragalactic maser studies are expected to flourish during the upcoming years. The following article provides a brief sketch of past achievements, ongoing projects and future perspectives.
The James Webb Space Telescope (JWST) will enable the detection of optical emission lines in galaxies spanning a broad range of luminosities out to redshifts z>10. Measurements of key galaxy properties, such as star formation rate and metallicity, through these observations will provide unique insight into, e.g., the role of feedback from stars and active galactic nuclei (AGNs) in regulating galaxy evolution, the co-evolution of AGNs and host galaxies, the physical origin of the main sequence of star-forming galaxies and the contribution by star-forming galaxies to cosmic reionization. We present an original framework to simulate and analyse observations performed with the Near Infrared Spectrograph (NIRSpec) on board JWST. We use the BEAGLE tool (BayEsian Analysis of GaLaxy sEds) to build a semi-empirical catalogue of galaxy spectra based on photometric spectral energy distributions (SEDs) of dropout galaxies in the Hubble Ultra Deep Field (HUDF). We demonstrate that the resulting catalogue of galaxy spectra satisfies different types of observational constraints on high redshift galaxies, and use it as input to simulate NIRSpec/prism (R~100) observations. We show that a single deep (~100 ks) NIRSpec/prism pointing in the HUDF will enable S/N>3 detections of multiple optical emission lines in ~30 (~60) galaxies at z>6 (z~4-6) down to m_F160W<30 AB mag. Such observations will allow measurements of galaxy star formation rates, ionization parameters and gas-phase metallicities within factors of 1.5, mass-to-light ratios within a factor of 2, galaxy ages within a factor of 3 and V-band attenuation optical depths with a precision of 0.3.
Deep surveys of the cosmic X-ray background are reviewed in the context of observational progress enabled by the Chandra X-ray Observatory and the X-ray Multi-Mirror Mission-Newton. The sources found by deep surveys are described along with their redshift and luminosity distributions, and the effectiveness of such surveys at selecting active galactic nuclei (AGN) is assessed. Some key results from deep surveys are highlighted including (1) measurements of AGN evolution and the growth of supermassive black holes, (2) constraints on the demography and physics of high-redshift AGN, (3) the X-ray AGN content of infrared and submillimeter galaxies, and (4) X-ray emission from distant starburst and normal galaxies. We also describe some outstanding problems and future prospects for deep extragalactic X-ray surveys.
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