Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userConstraint on the inflow/outflow rates in star-forming galaxies at z~1.4 from molecular gas observations
236
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We constrain the rate of gas inflow into and outflow from a main-sequence star-forming galaxy at z~1.4 by fitting a simple analytic model for the chemical evolution in a galaxy to the observational data of the stellar mass, metallicity, and molecular gas mass fraction. The molecular gas mass is derived from CO observations with a metallicity-dependent CO-to-H2 conversion factor, and the gas metallicity is derived from the H{alpha} and [NII]{lambda} 6584 emission line ratio. Using a stacking analysis of CO integrated intensity maps and the emission lines of H{alpha} and [NII], the relation between stellar mass, metallicity, and gas mass fraction is derived. We constrain the inflow and outflow rates with least-chi-square fitting of a simple analytic chemical evolution model to the observational data. The best-fit inflow and outflow rates are ~1.7 and ~0.4 in units of star-formation rate, respectively. The inflow rate is roughly comparable to the sum of the star-formation rate and outflow rate, which supports the equilibrium model for galaxy evolution; i.e., all inflow gas is consumed by star formation and outflow.
rate research
Read More
We try to constrain the gas inflow and outflow rate of star-forming galaxies at $zsim1.4$ by employing a simple analytic model for the chemical evolution of galaxies. The sample is constructed based on a large near-infrared (NIR) spectroscopic sample observed with Subaru/FMOS. The gas-phase metallicity is measured from the [ion{N}{2}]$lambda$6584/H$alpha$ emission line ratio and the gas mass is derived from the extinction corrected H$alpha$ luminosity by assuming the Kennicutt-Schmidt law. We constrain the inflow and outflow rate from the least-$chi^{2}$ fittings of the observed gas mass fraction, stellar mass, and metallicity with the analytic model. The joint $chi^{2}$ fitting shows the best-fit inflow rate is $sim1.8$ and the outflow rate is $sim0.6$ in unit of star-formation rate (SFR). By applying the same analysis to the previous studies at $zsim0$ and $zsim2.2$, it is shown that the both inflow rate and outflow rate decrease with decreasing redshift, which implies the higher activity of gas flow process at higher redshift. The decreasing trend of the inflow rate from $zsim2.2$ to $zsim0$ agrees with that seen in the previous observational works with different methods, though the absolute value is generally larger than the previous works. The outflow rate and its evolution from $zsim2.2$ to $zsim0$ obtained in this work agree well with the independent estimations in the previous observational works.
We present deep observations of a $z=1.4$ massive, star-forming galaxy in molecular and ionized gas at comparable spatial resolution (CO 3-2, NOEMA; H$alpha$, LBT). The kinematic tracers agree well, indicating that both gas phases are subject to the same gravitational potential and physical processes affecting the gas dynamics. We combine the one-dimensional velocity and velocity dispersion profiles in CO and H$alpha$ to forward-model the galaxy in a Bayesian framework, combining a thick exponential disk, a bulge, and a dark matter halo. We determine the dynamical support due to baryons and dark matter, and find a dark matter fraction within one effective radius of $f_{rm DM}(leq$$R_{e})=0.18^{+0.06}_{-0.04}$. Our result strengthens the evidence for strong baryon-dominance on galactic scales of massive $zsim1-3$ star-forming galaxies recently found based on ionized gas kinematics alone.
SPT0311-58 is the most massive infrared luminous system discovered so far during the Epoch of Reionization (EoR). In this paper, we present a detailed analysis of the molecular interstellar medium at z = 6.9, through high-resolution observations of the CO(6-5), CO(7-6), CO(10-9), [CI](2-1), and p-H2O(211-202) lines and dust continuum emission with the Atacama Large Millimeter/submillimeter Array (ALMA). The system consists of a pair of intensely star-forming gravitationally lensed galaxies (labelled West and East). The intrinsic far-infrared luminosity is (16 $pm$ 4)$timesrm 10^{12} rm L_{odot}$ in West and (27 $pm$ 4)$timesrm 10^{11} rm L_{odot}$ in East. We model the dust, CO, and [CI] using non-local thermodynamic equilibrium radiative transfer models and estimate the intrinsic gas mass to be (5.4 $pm$ 3.4)$timesrm 10^{11} rm M_{odot}$ in West and (3.1 $pm$ 2.7)$timesrm 10^{10} rm M_{odot}$ in East. We find that the CO spectral line energy distribution in West and East are typical of high-redshift sub-millimeter galaxies (SMGs). The CO-to-H2 conversion factor ($alpha_{CO}$) and the gas depletion time scales estimated from the model are consistent with the high-redshift SMGs in the literature within the uncertainties. We find no evidence of evolution of depletion time with redshift in SMGs at z > 3. This is the most detailed study of molecular gas content of a galaxy in the EoR to-date, with the most distant detection of H2O in a galaxy without any evidence for active galactic nuclei in the literature.
We study the molecular gas content of 24 star-forming galaxies at $z=3-4$, with a median stellar mass of $10^{9.1}$ M$_{odot}$, from the MUSE Hubble Ultra Deep Field (HUDF) Survey. Selected by their Lyman-alpha-emission and H-band magnitude, the galaxies show an average EW $approx 20$ angstrom, below the typical selection threshold for Lyman Alpha Emitters (EW $> 25$ angstrom), and a rest-frame UV spectrum similar to Lyman Break Galaxies. We use rest-frame optical spectroscopy from KMOS and MOSFIRE, and the UV features observed with MUSE, to determine the systemic redshifts, which are offset from Lyman alpha by 346 km s$^{-1}$, with a 100 to 600 km s$^{-1}$ range. Stacking CO(4-3) and [CI](1-0) (and higher-$J$ CO lines) from the ALMA Spectroscopic Survey of the HUDF (ASPECS), we determine $3sigma$ upper limits on the line luminosities of $4.0times10^{8}$ K km s$^{-1}$pc$^{2}$ and $5.6times10^{8}$ K km s$^{-1}$pc$^{2}$, respectively (for a 300 km s$^{-1}$ linewidth). Stacking the 1.2 mm and 3 mm dust continuum flux densities, we find a $3sigma$ upper limits of 9 $mu$Jy and $1.2$ $mu$Jy, respectively. The inferred gas fractions, under the assumption of a Galactic CO-to-H$_{2}$ conversion factor and gas-to-dust ratio, are in tension with previously determined scaling relations. This implies a substantially higher $alpha_{rm CO} ge 10$ and $delta_{rm GDR} ge 1200$, consistent with the sub-solar metallicity estimated for these galaxies ($12 + log(O/H) approx 7.8 pm 0.2$). The low metallicity of $z ge 3$ star-forming galaxies may thus make it very challenging to unveil their cold gas through CO or dust emission, warranting further exploration of alternative tracers, such as [CII].
We conducted observations of 12CO(J=5-4) and dust thermal continuum emission toward twenty star-forming galaxies on the main sequence at z~1.4 using ALMA to investigate the properties of the interstellar medium. The sample galaxies are chosen to trace the distributions of star-forming galaxies in diagrams of stellar mass-star formation rate and stellar mass-metallicity. We detected CO emission lines from eleven galaxies. The molecular gas mass is derived by adopting a metallicity-dependent CO-to-H2 conversion factor and assuming a CO(5-4)/CO(1-0) luminosity ratio of 0.23. Molecular gas masses and its fractions (molecular gas mass/(molecular gas mass + stellar mass)) for the detected galaxies are in the ranges of (3.9-12) x 10^{10} Msun and 0.25-0.94, respectively; these values are significantly larger than those in local spiral galaxies. The molecular gas mass fraction decreases with increasing stellar mass; the relation holds for four times lower stellar mass than that covered in previous studies, and that the molecular gas mass fraction decreases with increasing metallicity. Stacking analyses also show the same trends. The dust thermal emissions were clearly detected from two galaxies and marginally detected from five galaxies. Dust masses of the detected galaxies are (3.9-38) x 10^{7} Msun. We derived gas-to-dust ratios and found they are 3-4 times larger than those in local galaxies. The depletion times of molecular gas for the detected galaxies are (1.4-36) x 10^{8} yr while the results of the stacking analysis show ~3 x 10^{8} yr. The depletion time tends to decrease with increasing stellar mass and metallicity though the trend is not so significant, which contrasts with the trends in local galaxies.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
