10 research outputs found
Constraining the Minimum Luminosity of High Redshift Galaxies through Gravitational Lensing
We simulate the effects of gravitational lensing on the source count of high
redshift galaxies as projected to be observed by the Hubble Frontier Fields
program and the James Webb Space Telescope (JWST) in the near future. Taking
the mass density profile of the lensing object to be the singular isothermal
sphere (SIS) or the Navarro-Frenk-White (NFW) profile, we model a lens residing
at a redshift of z_L = 0.5 and explore the radial dependence of the resulting
magnification bias and its variability with the velocity dispersion of the
lens, the photometric sensitivity of the instrument, the redshift of the
background source population, and the intrinsic maximum absolute magnitude
(M_{max}) of the sources. We find that gravitational lensing enhances the
number of galaxies with redshifts z >= 13 detected in the angular region
\theta_E/2 <= \theta <= 2\theta_E (where \theta_E is the Einstein angle) by a
factor of ~ 3 and 1.5 in the HUDF (df/d\nu_0 ~ 9 nJy) and medium-deep JWST
surveys (df/d\nu_0 ~ 6 nJy). Furthermore, we find that even in cases where a
negative magnification bias reduces the observed number count of background
sources, the lensing effect improves the sensitivity of the count to the
intrinsic faint-magnitude cut-off of the Schechter luminosity function. In a
field centered on a strong lensing cluster, observations of z >= 6 and z >= 13
galaxies with JWST can be used to infer this cut-off magnitude for values as
faint as M_{max} ~ -14.4 and -16.1 mag (L_{min} ~ 2.5*10^{26} and 1.2*10^{27}
erg s^{-1} Hz^{-1}) respectively, within the range bracketed by existing
theoretical models. Gravitational lensing may therefore offer an effective way
of constraining the low-luminosity cut-off of high-redshift galaxies.Comment: 19 pages, 8 figures (JCAP, submitted
Recommended from our members
Predicting the intensity mapping signal for multi-J CO lines
We present a novel approach to estimating the intensity mapping signal of any CO rotational line emitted during the Epoch of Reionization (EoR). Our approach is based on large velocity gradient (LVG) modeling, a radiative transfer modeling technique that generates the full CO spectral line energy distribution (SLED) for a specified gas kinetic temperature, volume density, velocity gradient, molecular abundance, and column density. These parameters, which drive the physics of CO transitions and ultimately dictate the shape and amplitude of the CO SLED, can be linked to the global properties of the host galaxy, mainly the star formation rate (SFR) and the SFR surface density. By further employing an empirically derived SFR-M relation for high redshift galaxies, we can express the LVG parameters, and thus the specific intensity of any CO rotational transition, as functions of the host halo mass M and redshift z. Integrating over the range of halo masses expected to host CO-luminous galaxies, we predict a mean CO(1-0) brightness temperature ranging from ~0.6 {\mu}K at z= 6 to ~0.03 {\mu} at z= 10 with brightness temperature fluctuations of Δ2CO ~ 0.1 and 0.005 {\mu}K respectively, at k = 0.1 Mpc−1. In this model, the CO emission signal remains strong for higher rotational levels at z = 6, with ~ 0.3 and 0.05 {\mu}K for the CO J = 6->5 and CO J = 10->9 transitions respectively. Including the effects of CO photodissociation in these molecular clouds, especially at low metallicities, results in the overall reduction in the amplitude of the CO signal, with the low- and high-J lines weakening by 2-20% and 10-45%, respectively, over the redshift range 4 < z < 10.Astronom
Spectral distortion of the CMB by the cumulative CO emission from galaxies throughout cosmic history
We show that the cumulative CO emission from galaxies throughout cosmic history distorts the spectrum of the cosmic microwave background (CMB) at a level that is well above the detection limit of future instruments, such as the Primordial Inflation Explorer (PIXIE). The modeled CO signal has a prominent bump in the frequency interval 100-200 GHz, with a characteristic peak intensity of ~ 2×10−23 W m−2 Hz−1 sr−1. Most of the CO foreground originates from modest redshifts, z ~ 2-5, and needs to be efficiently removed for more subtle distortions from the earlier universe to be detected.Astronom
Recommended from our members
CEMP stars: possible hosts to carbon planets in the early Universe
We explore the possibility of planet formation in the carbon-rich protoplanetary disks of carbon-enhanced metal-poor (CEMP) stars, possible relics of the early Universe. The chemically anomalous abundance patterns ([C/Fe] ≥ 0.7) in this subset of low-mass stars suggest pollution by primordial core-collapsing supernovae (SNe) ejecta that are particularly rich in carbon dust grains. By comparing the dust-settling timescale in the protoplanetary disks of CEMP stars to the expected disk lifetime (assuming dissipation via photoevaporation), we determine the maximum distance rmax from the host CEMP star at which carbon-rich planetesimal formation is possible, as a function of the host star's [C/H] abundance. We then use our linear relation between rmax and [C/H], along with the theoretical mass-radius relation derived for a solid, pure carbon planet, to characterize potential planetary transits across host CEMP stars. Given that the related transits are detectable with current and upcoming space-based transit surveys, we suggest initiating an observational program to search for carbon planets around CEMP stars in hopes of shedding light on the question of how early planetary systems may have formed after the Big Bang.Astronom