scholarly journals Ammonia Emission in Various Star-forming Environments: A Pilot Study of Planck Galactic Cold Clumps

2022 ◽  
Vol 258 (1) ◽  
pp. 17
Author(s):  
O. Fehér ◽  
L. Viktor Tóth ◽  
Alex Kraus ◽  
Rebeka Bőgner ◽  
Gwanjeong Kim ◽  
...  
Keyword(s):  
Velocity Dispersion ◽  
Gas Content ◽  
Ammonia Emission ◽  
Physical Parameters ◽  
Submillimeter Range ◽  
Physical Size ◽  
Star Forming ◽  
James Clerk Maxwell ◽  
Star Forming Regions ◽  
Varying Environments

Abstract The Planck Catalogue of Galactic Cold Clumps provides an all-sky sample of potential star-forming regions based on the submillimeter emission of their dust content. Around 1000 of these Planck objects were mapped with the James Clerk Maxwell telescope in the submillimeter range during the SCOPE survey, identifying prestellar and protostellar dense clumps inside them. We used the Effelsberg 100 m telescope to observe the emission lines of the NH3 inversion transitions toward a sample of 97 dense objects in varying environments in order to assess the physical parameters of their gas content. We derive their temperature, density, and velocity dispersion, correlating the resulting parameters with the environmental and evolutionary characteristics of the targets and with regard to their distance and physical size. We examine the dependence of physical parameters on distance and Galactic position and compare the gas-based and dust-continuum-based temperatures and densities. Together with the presence of maser emission and higher inversion transitions of ammonia, we may differentiate between certain groups of targets, e.g., filamentary, protostellar clumps, and high-latitude, core-sized, starless sources.

scholarly journals Molecular Gas in the Magellanic Clouds

1999 ◽  
Vol 190 ◽  
pp. 67-73 ◽  
Author(s):  
Mónica Rubio
Keyword(s):  
Line Emission ◽  
Magellanic Clouds ◽  
Gas Content ◽  
Molecular Gas ◽  
Star Forming ◽  
Physical Conditions ◽  
Star Forming Regions ◽  
Hydrogen Column Density ◽  
Spatial Coverage ◽  
Co Emission

The molecular gas content in the Magellanic Clouds has been studied, with different spatial coverage and resolution, through obervations of CO(1-0) line emission. In the LMC and the SMC the molecular gas is dominated by clouds whose properties are different from those of their Galactic counterparts. The relation between the intensity of CO emission and molecular hydrogen column density, or the conversion factor X, is different than that of molecular clouds in our Galaxy and depends on the ambient physical conditions. Studying the molecular gas through observations in the H2 emission line may prove an alternative way to determine the molecular content associated with star forming regions in the Magellanic Clouds. In particular, results obtained towards 30 Doradus in the LMC are presented.

scholarly journals A cautionary tale of attenuation in star-forming regions

2020 ◽  
Vol 494 (4) ◽  
pp. 4751-4770 ◽  
Author(s):  
Mallory Molina ◽  
Nikhil Ajgaonkar ◽  
Renbin Yan ◽  
Robin Ciardullo ◽  
Caryl Gronwall ◽  
...  
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Dust Content ◽  
Physical Parameters ◽  
Star Forming ◽  
Total Dust ◽  
Star Forming Regions ◽  
Field Unit

ABSTRACT The attenuation of light from star-forming galaxies is correlated with a multitude of physical parameters including star formation rate, metallicity and total dust content. This variation in attenuation is even more evident on kiloparsec scales, which is the relevant size for many current spectroscopic integral field unit surveys. To understand the cause of this variation, we present and analyse Swift/UVOT near-UV (NUV) images and SDSS/MaNGA emission-line maps of 29 nearby (z < 0.084) star-forming galaxies. We resolve kiloparsec-sized star-forming regions within the galaxies and compare their optical nebular attenuation (i.e. the Balmer emission line optical depth, $\tau ^{l}_{B}\equiv \tau _{\textrm {H}\beta }-\tau _{\textrm {H}\alpha }$) and NUV stellar continuum attenuation (via the NUV power-law index, β) to the attenuation law described by Battisti et al. We show the data agree with that model, albeit with significant scatter. We explore the dependence of the scatter of the β–$\tau ^{l}_{B}$ measurements from the star-forming regions on different physical parameters, including distance from the nucleus, star formation rate and total dust content. Finally, we compare the measured $\tau ^{l}_{B}$ and β values for the individual star-forming regions with those of the integrated galaxy light. We find a strong variation in β between the kiloparsec scale and the larger galaxy scale that is not seen in $\tau ^{l}_{B}$. We conclude that the sightline dependence of UV attenuation and the reddening of β due to the light from older stellar populations could contribute to the scatter in the β–$\tau ^{l}_{B}$ relation.

scholarly journals Star Formation in the Large Magellanic Cloud

1987 ◽  
Vol 115 ◽  
pp. 521-533
Author(s):  
J. V. Feitzinger
Keyword(s):  
Star Formation ◽  
Large Magellanic Cloud ◽  
Radio Continuum ◽  
Physical Parameters ◽  
Formation Processes ◽  
Star Forming ◽  
Star Forming Regions ◽  
Scale Structures ◽  
And Cluster Analysis ◽  
Spiral Arm

Methods used in pattern recognition and cluster analysis are applied to investigate the spatial distribution of the star forming regions. The fractal dimension of these structures is deduced. The new 21 cm, radio continuum (1.4 GHz) and IRAS surveys reveal scale structures of 700 pc to 1500 pc being identical with the optically identified star forming sites. The morphological structures delineated by young stars reflect physical parameters which determine the star formation in this galaxy. The formation of spiral arm filaments is understandable by stochastic selfpropagating star formation processes.

scholarly journals Kinematics of dense gas in the L1495 filament

2018 ◽  
Vol 617 ◽  
pp. A27 ◽  
Author(s):  
A. Punanova ◽  
P. Caselli ◽  
J. E. Pineda ◽  
A. Pon ◽  
M. Tafalla ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Magnetic Fields ◽  
Molecular Cloud ◽  
Large Scale ◽  
Velocity Dispersion ◽  
Star Forming ◽  
Star Forming Regions ◽  
Dense Cores ◽  
Velocity Gradients ◽  
Total Velocity

Context. Nitrogen bearing species, such as NH3, N2H+, and their deuterated isotopologues show enhanced abundances in CO-depleted gas, and thus are perfect tracers of dense and cold gas in star-forming regions. The Taurus molecular cloud contains the long L1495 filament providing an excellent opportunity to study the process of star formation in filamentary environments. Aims. We study the kinematics of the dense gas of starless and protostellar cores traced by the N2D+(2–1), N2H+(1–0), DCO+(2–1), and H13CO+(1–0) transitions along the L1495 filament and the kinematic links between the cores and surrounding molecular cloud. Methods. We measured velocity dispersions, local and total velocity gradients, and estimate the specific angular momenta of 13 dense cores in the four transitions using on-the-fly observations with the IRAM 30-m antenna. To study a possible connection to the filament gas, we used the C18O(1–0) observations. Results. The velocity dispersions of all studied cores are mostly subsonic in all four transitions and are similar and almost constant dispersion across the cores in N2D+(2–1) and N2H+(1–0). A small fraction of the DCO+(2–1) and H13CO+(1–0) lines show transonic dispersion and exhibit a general increase in velocity dispersion with line intensity. All cores have velocity gradients (0.6–6.1 km s−1 pc−1), typical of dense cores in low-mass star-forming regions. All cores show similar velocity patterns in the different transitions, simple in isolated starless cores, and complex in protostellar cores and starless cores close to young stellar objects where gas motions can be affected by outflows. The large-scale velocity field traced by C18O(1–0) does not show any perturbation due to protostellar feedback and does not mimic the local variations seen in the other four tracers. Specific angular momentum J∕M varies in a range (0.6–21.0) × 1020 cm2 s−1, which is similar to the results previously obtained for dense cores. The J∕M measured in N2D+(2–1) is systematically lower than J∕M measured in DCO+(2–1) and H13CO+(1–0). Conclusions. All cores show similar properties along the 10 pc-long filament. N2D+(2–1) shows the most centrally concentrated structure, followed by N2H+(1–0) and DCO+(2–1), which show similar spatial extent, and H13CO+(1–0). The non-thermal contribution to the velocity dispersion increases from higher to lower density tracers. The change of magnitude and direction of the total velocity gradients depending on the tracer used indicates that internal motions change at different depths within the cloud. N2D+ and N2H+ show smaller gradients than the lower density tracers DCO+ and H13CO+, implying a loss of specific angular momentum at small scales. At the level of cloud-core transition, the core’s external envelope traced by DCO+ and H13CO+ is spinning up, which is consistent with conservation of angular momentum during core contraction. C18O traces the more extended cloud material whose kinematics is not affected by the presence of dense cores. The decrease in specific angular momentum towards the centres of the cores shows the importance of local magnetic fields to the small-scale dynamics of the cores. The random distributions of angles between the total velocity gradient and large-scale magnetic field suggests that magnetic fields may become important only in high density gas within dense cores.

A Multiwavelength Study of Young Massive Star‐forming Regions. I. The Ionized Gas Content

2006 ◽  
Vol 651 (2) ◽  
pp. 914-932 ◽  
Author(s):  
Guido Garay ◽  
Kate J. Brooks ◽  
Diego Mardones ◽  
Ray P. Norris
Keyword(s):  
Massive Star ◽  
Gas Content ◽  
Ionized Gas ◽  
Star Forming ◽  
Star Forming Regions

scholarly journals Multiscale dynamics in star-forming regions: the interplay between gravity and turbulence

2019 ◽  
Vol 491 (3) ◽  
pp. 4310-4324 ◽  
Author(s):  
A Traficante ◽  
G A Fuller ◽  
A Duarte-Cabral ◽  
D Elia ◽  
M H Heyer ◽  
...  
Keyword(s):  
Surface Density ◽  
Velocity Dispersion ◽  
Spatial Scales ◽  
Critical Surface ◽  
Star Forming ◽  
Star Forming Regions ◽  
Multiscale Dynamics ◽  
Gravity Driven ◽  
Turbulent Cascade ◽  
Density Threshold

ABSTRACT In this work, we investigate the interplay between gravity and turbulence at different spatial scales and in different density regimes. We analyse a sample of 70-μm quiet clumps that are divided into three surface density bins, and we compare the dynamics of each group with the dynamics of their respective filaments. The densest clumps form within the densest filaments, on average, and they have the highest value of the velocity dispersion. The kinetic energy is transferred from the filaments down to the clumps most likely through a turbulent cascade, but we identify a critical value of the surface density, Σ ≃ 0.1 g cm−2, above which the dynamics change from being mostly turbulent-driven to mostly gravity-driven. The scenario we obtain from our data is a continuous interplay between turbulence and gravity, where the former creates structures at all scales and the latter takes the lead when the critical surface density threshold is reached. In the densest filaments, this transition can occur at the parsec, or even larger scales, leading to a global collapse of the whole region and most likely to the formation of the massive objects.

scholarly journals Measuring elemental abundance ratios in protoplanetary disks at millimeter wavelengths

2020 ◽  
Vol 638 ◽  
pp. A110 ◽  
Author(s):  
D. Fedele ◽  
C. Favre
Keyword(s):  
Protoplanetary Disks ◽  
Abundance Ratio ◽  
Elemental Abundance ◽  
Physical Parameters ◽  
Minor Effect ◽  
Line Flux ◽  
Nearby Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
A Minor

Over million years of evolution, gas dust and ice in protoplanetary disks can be chemically reprocessed. There is evidence that the gas-phase carbon and oxygen abundances are subsolar in disks belonging to nearby star forming regions. These findings have a major impact on the composition of the primary atmosphere of giant planets (but it may also be valid for super-Earths and sub-Neptunes) as they accrete their gaseous envelopes from the surrounding material in the disk. In this study, we performed a thermochemical modeling analysis with the aim of testing how reliable and robust are the estimates of elemental abundance ratios based on (sub)millimeter observations of molecular lines. We created a grid of disk models for the following different elemental abundance ratios: C/O, N/O, and S/O, and we computed the line flux of a set of carbon-nitrogen and sulphur-bearing species, namely CN, HCN, NO, C2H, c–C3H2, H2CO, HC3N, CH3CN, CS, SO, H2S, and H2CS, which have been detected with present (sub)millimeter facilities such as ALMA and NOEMA. We find that the line fluxes, once normalized to the flux of the 13CO J = 2−1 line, are sensitive to the elemental abundance ratios. On the other hand, the stellar and disk physical parameters have only a minor effect on the line flux ratios. Our results demonstrate that a simultaneous analysis of multiple molecular transitions is a valid approach to constrain the elemental abundance ratio in protoplanetary disks.

scholarly journals Physics and chemistry of hot molecular cores

2006 ◽  
Vol 2 (S237) ◽  
pp. 148-154 ◽  
Author(s):  
H. Beuther
Keyword(s):  
Accretion Disks ◽  
Massive Star ◽  
Small Scale ◽  
High Angular Resolution ◽  
Physical Parameters ◽  
Molecular Gas ◽  
Star Forming ◽  
Star Forming Regions ◽  
Molecular Lines ◽  
The Right

AbstractYoung massive star-forming regions are known to produce hot molecular gas cores (HMCs) with a rich chemistry. While this chemistry is interesting in itself, it also allows to investigate important physical parameters. I will present recent results obtained with high-angular-resolution interferometers disentangling the small-scale structure and complexity of various molecular gas components. Early attempts to develop a chemical evolutionary sequence are discussed. Furthermore, I will outline the difficulty to isolate the right molecular lines capable to unambiguously trace potential massive accretion disks.

scholarly journals Multiwavelength dissection of a massive heavily dust-obscured galaxy and its blue companion at z∼2

2021 ◽  
Vol 646 ◽  
pp. A127
Author(s):  
M. Hamed ◽  
L. Ciesla ◽  
M. Béthermin ◽  
K. Małek ◽  
E. Daddi ◽  
...  
Keyword(s):  
Star Formation ◽  
Spectral Energy Distribution ◽  
Gas Content ◽  
Spectral Energy ◽  
Physical Parameters ◽  
Molecular Gas ◽  
Star Forming ◽  
Attenuation Law ◽  
Star Formation Activity ◽  
Attenuation Laws

Aims. We study a system of two galaxies, Astarte and Adonis, at z ∼ 2. At this time, the Universe was undergoing the peak of its star formation activity. Astarte is a dusty star-forming galaxy at the massive end of the main sequence (MS), and Adonis is a less massive companion galaxy that is bright in the ultraviolet and has an optical spectroscopic redshift. We investigate whether this ultramassive galaxy is quenching, and whether it has always been on the MS of star-forming galaxies. Methods. We used the code CIGALE to model the spectral energy distribution. The code relies on the energetic balance between the ultraviolet and the infrared. We derived some of the key physical properties of Astarte and Adonis, mainly their star formation rates (SFRs), stellar masses, and dust luminosities. We inspected the variation of the physical parameters depending on the assumed dust-attenuation law. We also estimated the molecular gas mass of Astarte from its CO emission, using different αCO and transition ratios (r31), and we discuss the implication of the various assumptions on the gas-mass derivation. Reults. We find that Astarte exhibits a MS-like star formation activity, and Adonis is undergoing a strong starburst phase. The molecular gas mass of Astarte is far lower than the gas fraction of typical star-forming galaxies at z = 2. This low gas content and high SFR result in a depletion time of 0.22 ± 0.07 Gyr, which is slightly shorter than expected for a MS galaxy at this redshift. The CO luminosity relative to the total infrared luminosity suggests a MS-like activity when we assume a galactic conversion factor and a low transition ratio. The SFR of Astarte is on the same order when different attenuation laws are used, unlike its stellar mass, which increases when shallow attenuation laws are used (∼1 × 1011 M⊙ assuming a Calzetti relation, versus ∼4 × 1011 M⊙ assuming a shallow attenuation law). We discuss these properties and suggest that Astarte might be experiencing a recent decrease in star formation activity and is quenching through the MS following a starburst epoch.

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