Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userA Survey of Atomic Carbon at High Redshift
90
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We present a survey of atomic carbon (CI) emission in high-redshift (z>2) submillimeter galaxies (SMGs) and quasar host galaxies (QSOs). Sensitive observations of the CI(3P_1->3P_0) and CI(3P_2->3P_1) lines have been obtained at the IRAM Plateau de Bure interferometer and the IRAM 30m telescope. A total of 16 CI lines have been targeted in 10 sources, leading to a total of 10 detected lines --- this doubles the number of CI observations at high redshift to date. We include previously published CI observations (an additional 5 detected sources) in our analysis. Our main finding is that the CI properties of the studied high-redshift systems do not differ significantly from what is found in low-redshift systems, including the Milky Way. The CI(3P_2->3P_1)/CI(3P_1->3P_0) and the CI(3P_1->3P_0)/12CO(3-2) line luminosity (L) ratios change little in our sample, with respective ratios of 0.55+/-0.15 and 0.32+/-0.13. The CI lines are not an important contributor to cooling of the molecular gas (average L_CI/L_FIR ~ (7.7+/-4.6) x 10^-6). We derive a mean carbon excitation temperature of 29.1+/-6.3 K, broadly consistent with dust temperatures derived for high-redshift starforming systems, but lower than gas temperatures typically derived for starbursts in the local universe. The carbon abundance of X_CI/X_H2~8.4+/-3.5 x 10^-5 is of the same order as found in the Milky Way and nearby galaxies. This implies that the high-z galaxies studied here are significantly enriched in carbon on galactic scales, even though the look-back times are considerable (the average redshift of the sample sources corresponds to an age of the universe of ~2 Gyr).
rate research
Read More
We present the first results of an ALMA survey of the lower fine structure line of atomic carbon [C I]$(^3P_1,-,^{3}P_0)$ in far infrared-selected galaxies on the main sequence at $zsim1.2$ in the COSMOS field. We compare our sample with a comprehensive compilation of data available in the literature for local and high-redshift starbursting systems and quasars. We show that the [C I]($^3P_1$$rightarrow$$^3P_0$) luminosity correlates on global scales with the infrared luminosity $L_{rm IR}$ similarly to low-$J$ CO transitions. We report a systematic variation of $L_{rm [C,I]^3P_1,-, ^3P_0}$/$L_{rm IR}$ as a function of the galaxy type, with the ratio being larger for main-sequence galaxies than for starbursts and sub-millimeter galaxies at fixed $L_{rm IR}$. The $L_{rm [C,I]^3P_1,-, ^3P_0}$/$L_{rm CO(2-1)}$ and $M_{rm{[C I]}}$/$M_{rm dust}$ mass ratios are similar for main-sequence galaxies and for local and high-redshift starbursts within a 0.2 dex intrinsic scatter, suggesting that [C I] is a good tracer of molecular gas mass as CO and dust. We derive a fraction of $f_{rm{[C,I]}} = M_{rm{[C,I]}} / M_{rm{C}}sim3-13$% of the total carbon mass in the atomic neutral phase. Moreover, we estimate the neutral atomic carbon abundance, the fundamental ingredient to calibrate [C I] as a gas tracer, by comparing $L_{rm [C,I]^3P_1,-, ^3P_0}$ and available gas masses from CO lines and dust emission. We find lower [C I] abundances in main-sequence galaxies than in starbursting systems and sub-millimeter galaxies, as a consequence of the canonical $alpha_{rm CO}$ and gas-to-dust conversion factors. This argues against the application to different galaxy populations of a universal standard [C I] abundance derived from highly biased samples.
We report the detection of the 3P1 to 3P0 fine-structure line of neutral carbon in the z=4.12 quasar PSS 2322+1944, obtained at the IRAM Plateau de Bure interferometer. The CI 3P1-3P0 line is detected with a signal-to-noise ratio of about 6 with a peak intensity of about 2.5 mJy and a velocity-integrated line flux of 0.81+-0.12 Jy.km/s. Assuming an excitation temperature of 43 K (equal to the dust temperature), we derive a mass of neutral carbon (corrected for magnification) of about 1.2e7 Msun. In PSS 2322+1944, the cooling due to C is about 6 times smaller than for CO, whereas the CO and C cooling represents about 1e-4 of the far-infrared continuum and more than half of the cooling due to C+.
An observational program focused on the high redshift ($2<z<6$) Universe has the opportunity to dramatically improve over upcoming LSS and CMB surveys on measurements of both the standard cosmological model and its extensions. Using a Fisher matrix formalism that builds upon recent advances in Lagrangian perturbation theory, we forecast constraints for future spectroscopic and 21-cm surveys on the standard cosmological model, curvature, neutrino mass, relativistic species, primordial features, primordial non-Gaussianity, dynamical dark energy, and gravitational slip. We compare these constraints with those achievable by current or near-future surveys such as DESI and Euclid, all under the same forecasting formalism, and compare our formalism with traditional linear methods. Our Python code FishLSS $-$ used to calculate the Fisher information of the full shape power spectrum, CMB lensing, the cross-correlation of CMB lensing with galaxies, and combinations thereof $-$ is publicly available.
The rate evolution of subluminous Type Ia Supernovae is presented using data from the Supernova Legacy Survey. This sub-sample represents the faint and rapidly-declining light-curves of the observed supernova Ia (SN Ia) population here defined by low stretch values (s<0.8). Up to redshift z=0.6, we find 18 photometrically-identified subluminous SNe Ia, of which six have spectroscopic redshift (and three are spectroscopically-confirmed SNe Ia). The evolution of the subluminous volumetric rate is constant or slightly decreasing with redshift, in contrast to the increasing SN Ia rate found for the normal stretch population, although a rising behaviour is not conclusively ruled out. The subluminous sample is mainly found in early-type galaxies with little or no star formation, so that the rate evolution is consistent with a galactic mass dependent behavior: $r(z)=Atimes M_g$, with $A=(1.1pm0.3)times10^{-14}$ SNe per year and solar mass.
A new method is used to measure the physical conditions of the gas in damped Lyman-alpha systems (DLAs). Using high resolution absorption spectra of a sample of 80 DLAs, we are able to measure the ratio of the upper to lower fine-structure levels of the ground state of C II and Si II. These ratios are determined solely by the physical conditions of the gas. We explore the allowed physical parameter space using a Monte Carlo Markov Chain method to constrain simultaneously the temperature, neutral hydrogen density, and electron density of each DLA. The results indicate that at least 5 % of all DLAs have the bulk of their gas in a dense, cold phase with typical densities of ~100 cm-3 and temperatures below 500 K. We further find that the typical pressure of DLAs in our sample is log(P/k) = 3.4 [K cm-3], which is comparable to the pressure of the local interstellar medium (ISM), and that the components containing the bulk of the neutral gas can be quite small with absorption sizes as small as a few parsec. We show that the majority of the systems are consistent with having densities significantly higher than expected from a purely canonical WNM, indicating that significant quantities of dense gas (i.e. n_H > 0.1 cm-3) are required to match observations. Finally, we identify 8 systems with positive detections of Si II*. These systems have pressures (P/k) in excess of 20000 K cm-3, which suggest that these systems tag a highly turbulent ISM in young, star-forming galaxies.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
