Abstract
This paper provides an update of our previous scaling relations between galaxy-integrated molecular gas masses, stellar masses, and star formation rates (SFRs), in the framework of the star ...formation main sequence (MS), with the main goal of testing for possible systematic effects. For this purpose our new study combines three independent methods of determining molecular gas masses from CO line fluxes, far-infrared dust spectral energy distributions, and ∼1 mm dust photometry, in a large sample of 1444 star-forming galaxies between
z
= 0 and 4. The sample covers the stellar mass range log(
M
*
/
M
⊙
) = 9.0–11.8, and SFRs relative to that on the MS,
δ
MS = SFR/SFR(MS), from 10
−1.3
to 10
2.2
. Our most important finding is that all data sets, despite the different techniques and analysis methods used, follow the same scaling trends, once method-to-method zero-point offsets are minimized and uncertainties are properly taken into account. The molecular gas depletion time
t
depl
, defined as the ratio of molecular gas mass to SFR, scales as (1 +
z
)
−0.6
× (
δ
MS)
−0.44
and is only weakly dependent on stellar mass. The ratio of molecular to stellar mass
μ
gas
depends on (
1
+
z
)
2.5
×
(
δ
MS
)
0.52
×
(
M
*
)
−
0.36
, which tracks the evolution of the specific SFR. The redshift dependence of
μ
gas
requires a curvature term, as may the mass dependences of
t
depl
and
μ
gas
. We find no or only weak correlations of
t
depl
and
μ
gas
with optical size
R
or surface density once one removes the above scalings, but we caution that optical sizes may not be appropriate for the high gas and dust columns at high
z
.
The Cii 158 ...m emission line can arise in all phases of the interstellar medium (ISM), therefore being able to disentangle the different contributions is an important yet unresolved problem when ...undertaking galaxy-wide, integrated Cii observations. We present a new multiphase 3D radiative transfer interface that couples starburst99, a stellar spectrophotometric code, with the photoionization and astrochemistry codes mocassin and 3d-pdr. We model entire star-forming regions, including the ionized, atomic, and molecular phases of the ISM, and apply a Bayesian inference methodology to parametrize how the fraction of the Cii emission originating from molecular regions, f sub( CII,mol), varies as a function of typical integrated properties of galaxies in the local Universe. The main parameters responsible for the variations of f sub( CII,mol) are specific star formation rate (SSFR), gas phase metallicity, H ii region electron number density (n sub( e)), and dust mass fraction. For example, f sub( CII,mol) can increase from 60 to 80 per cent when either n sub( e) increases from 10 super( 1.5) to 10 super( 2.5) cm super( -3), or SSFR decreases from 10 super( -9.6) to 10 super( -10.6) yr super( -1). Our model predicts for the Milky Way that f sub( CII,mol) = 75.8 plus or minus 5.9 per cent, in agreement with the measured value of 75 per cent. When applying the new prescription to a complete sample of galaxies from the Herschel Reference Survey, we find that anywhere from 60 to 80 per cent of the total integrated Cii emission arises from molecular regions. (ProQuest: ... denotes formulae/symbols omitted.)
ABSTRACT
Scaling laws of dust, H i gas, and metal mass with stellar mass, specific star formation rate, and metallicity are crucial to our understanding of the build-up of galaxies through their ...enrichment with metals and dust. In this work, we analyse how the dust and metal content varies with specific gas mass (MH i/M⋆) across a diverse sample of 423 nearby galaxies. The observed trends are interpreted with a set of Dust and Element evolUtion modelS (DEUS) – including stellar dust production, grain growth, and dust destruction – within a Bayesian framework to enable a rigorous search of the multidimensional parameter space. We find that these scaling laws for galaxies with −1.0 ≲ log MH i/M⋆ ≲ 0 can be reproduced using closed-box models with high fractions (37–89 ${{\ \rm per\ cent}}$) of supernova dust surviving a reverse shock, relatively low grain growth efficiencies (ϵ = 30–40), and long dust lifetimes (1–2 Gyr). The models have present-day dust masses with similar contributions from stellar sources (50–80 ${{\ \rm per\ cent}}$) and grain growth (20–50 ${{\ \rm per\ cent}}$). Over the entire lifetime of these galaxies, the contribution from stardust (>90 ${{\ \rm per\ cent}}$) outweighs the fraction of dust grown in the interstellar medium (<10 ${{\ \rm per\ cent}}$). Our results provide an alternative for the chemical evolution models that require extremely low supernova dust production efficiencies and short grain growth time-scales to reproduce local scaling laws, and could help solving the conundrum on whether or not grains can grow efficiently in the interstellar medium.
Abstract
We present Herschel PACS observations of the C ii 158 μm emission line in a sample of 24 intermediate mass (9 < log M
*/M⊙ < 10) and low metallicity (0.4 < Z/Z⊙ < 1.0) galaxies from the ...xCOLD GASS survey. In combination with IRAM CO (1−0) measurements, we establish scaling relations between integrated and molecular region
$L_{{C\,\small {\rm II}}}$
/L
CO (1–0) ratios as a function of integrated galaxy properties. A Bayesian analysis reveals that only two parameters, metallicity and offset from the main sequence, Δ(MS), are needed to quantify variations in the luminosity ratio; metallicity describes the total dust content available to shield CO from UV radiation, while Δ(MS) describes the strength of this radiation field. We connect the
$L_{{C\,\small {\rm II}}}$
/L
CO (1–0) ratio to the CO-to-H2 conversion factor and find a multivariate conversion function, which can be used up to z ∼ 2.5. This function depends primarily on metallicity, with a second-order dependence on Δ(MS). We apply this to the full xCOLD GASS and PHIBSS1 surveys and investigate molecular gas scaling relations. We find a flattening of the relation between gas mass fraction and stellar mass at log M
* < 10.0. While the molecular gas depletion time varies with sSFR, it is mostly independent of mass, indicating that the low L
CO/SFR ratios long observed in low-mass galaxies are entirely due to photodissociation of CO and not to an enhanced star formation efficiency.
Introduction The laryngeal mask cuff inflation can exert a pressure and a displacement on the neck vessels and determine a potential change of the carotid flow. The study exami- ned the effects of ...cuff inflation of a ProSeal Laryngeal Mask Airway on the carotid bulb during sevoflurane in-duction in pediatric population. Materials and Methods The measurement of some hemodynamic parameters (cross-sectional area carotid artery, resistance index, carotid flow acceleration, systolic and diastolic peak velo- city, SDR S/D Ratio: Systolic Peak Velocity / End Diastolic Velocity) were performed bilaterally before and after laryngeal mask cuff inflation by color Doppler ultrasound at the level of the carotid artery bulb during sevoflurane induction in pediatric patients undergoing surgery. A ProSeal laryngeal mask was used in this study as it has a better leak pressure versus the classic laryngeal mask airway. Results Results showed that there was no clinically and statistically significant variation in measured parameters befo- re and after laryngeal mask cuff inflation Conclusion The results demonstrated that in children during sevo- flurane induction, differently from other studies descri- bed in literature, laryngeal mask cuff inflation does not reduce or change the carotid flow and all other hemodynamic parameters.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
This paper provides an update of our previous scaling relations between galaxy-integrated molecular gas masses, stellar masses, and star formation rates (SFRs), in the framework of the star formation ...main sequence (MS), with the main goal of testing for possible systematic effects. For this purpose our new study combines three independent methods of determining molecular gas masses from CO line fluxes, far-infrared dust spectral energy distributions, and ∼1 mm dust photometry, in a large sample of 1444 star-forming galaxies between z = 0 and 4. The sample covers the stellar mass range log(M*/M ) = 9.0-11.8, and SFRs relative to that on the MS, δMS = SFR/SFR(MS), from 10−1.3 to 102.2. Our most important finding is that all data sets, despite the different techniques and analysis methods used, follow the same scaling trends, once method-to-method zero-point offsets are minimized and uncertainties are properly taken into account. The molecular gas depletion time tdepl, defined as the ratio of molecular gas mass to SFR, scales as (1 + z)−0.6 × (δMS)−0.44 and is only weakly dependent on stellar mass. The ratio of molecular to stellar mass gas depends on ( 1 + z ) 2.5 × ( δ MS ) 0.52 × ( M * ) − 0.36 , which tracks the evolution of the specific SFR. The redshift dependence of gas requires a curvature term, as may the mass dependences of tdepl and gas. We find no or only weak correlations of tdepl and gas with optical size R or surface density once one removes the above scalings, but we caution that optical sizes may not be appropriate for the high gas and dust columns at high z.
The recently established equilibrium model for galaxy evolution gives major importance to the role of gas in regulating galaxy growth; the efficiency of star formation as gas is cycled in and out of ...galaxies is a central theme in this emergent picture. Low mass galaxies in the local universe, with their low metallicity environments, high gas mass fractions, and low LCO ratios, make them ideal and interesting candidates to test this SFR model. Several questions remain: How can we accurately trace the total molecular gas in sub-solar metallicity environments where photodissociation of CO occurs? Is there a fundamentally different star formation efficiency in these systems compared to their high mass counterparts? This Thesis answers these questions using a new multiwavelength data set based on the IRAM xCOLD GASS survey, alongside auxiliary CII 158um line spectroscopy observations, using PACS on-board Herschel, with a newly built multi-phase ISM Radiative Transfer model and robust statistical methods. To accurately trace molecular gas in sub-solar metallicity environments we wish to use the CII emission line to quantify the CO-dark H2 gas however, as the CII 158μm emission line can arise in all phases of the ISM, being able to disentangle the different ISM contributions is an important yet unresolved problem when undertaking galaxy-wide, integrated CII observations. We first present a new multi-phase 3D Radiative Transfer interface that couples starburst99, a stellar spectrophotometric code, with the photoionisation and astrochemistry codes Mocassin and 3d-pdr. We model entire star forming regions, including the ionised, atomic and molecular phases of the ISM, and apply a Bayesian inference methodology to parametrise how the fraction of the CII emission originating from molecular regions, fCII,mol, varies as a function of typical integrated properties of galaxies in the local Universe.  Once this has been achieved we present the first results using xCOLD GASS, a legacy survey of molecular gas in nearby galaxies, now extending down to stellar masses of 109M⊙ from its precursor survey COLD GASS. Using the IRAM 30m telescope we measure the CO(1−0) line and, with Herschel PACS observations, measure the CII 158μm emission line in a sub-sample of 24 intermediate mass (9 < log M∗/M⊙ < 10) and low metallicity (0.4 < Z/Z⊙ < 1.0) galaxies. We provide the first scaling relations for the integrated and molecular region LCII/LCO(1-0) ratio as a function of galaxy properties. We connect the LCII/LCO(1-0) ratio to the CO-to-H2 conversion factor and find a multivariate con- version function, which can be used up to z∼2.5. We then apply this to the full xCOLD GASS and PHIBSS1 surveys and investigate molecular gas scaling relations across red- shifts, aiming to test the equilibrium model. Finally we discuss ongoing survey planning and the latest software development for the ongoing JINGLE survey, which aims to simultaneously quantify gas and dust content for a large sample of galaxies. By conducting such a survey we shall be able to investigate how quantities such as the dust temperature, emissivity and dust-to-gas ratio vary systematically across the galaxy population; refining an alternative method to quantify gas masses of galaxies. The first results from JINGLE are presented, demonstrating the potential of the survey and highlighting the work carried out by this author.
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