scholarly journals 12C18O in OMC-1: Kinematics, Molecular Column Density, and Kinetic Temperature Distribution

1987 ◽  
Vol 115 ◽  
pp. 145-146
Author(s):  
T. L. Wilson ◽  
E. Serabyn ◽  
C. Henkel ◽  
C. M. Walmsley
Keyword(s):  
Column Density ◽  
Angular Resolution ◽  
Dust Emission ◽  
Line Emission ◽  
Molecular Gas ◽  
Kinetic Temperature ◽  
Line Profiles ◽  
Co Emission ◽  
Continuous Strip ◽  
Made In

A fully sampled map of size ∼1′×3′ (R.A. Dec), centered on BN-KL has been made in the J = 1-0 line of 12C18O with 21″ angular resolution. The 12C18O emission is concentrated in a ← 40″ wide continuous strip running S to NE. Several maxima are superposed on the ridge, but none exceeds the average emission level by more than 40%. There is no intense peak of 12C18O J = 1-0 line emission centered on BN-KL, in contrast to maps of the dust emission. The dust and 12C18O results can be reconciled with a constant (CO/H2) ratio if there are variations in the kinetic temperature and column density of ∼50%. Peaks in both temperature and column density are then located near BN-KL, and 90″ to the south. From the estimated CO column density, about 10% of the carbon is in the form of CO. Near the BN-KL region, the 12C18O line profiles tend to become wider. These wider lines appear to be superposed on a weak, 18 km s−1 (FWHP) wide pedestal. In regions 40″ NE and 30″ S of BN-KL, the 12C18O lines have widths of less than 2 km s−1. Presumably, these are the locations of high density, quiescent molecular gas. The radial velocity of the CO emission increases from 6.5 km s−1 (at 90″ S) to 10.5 km s−1 (at 60″ NE) of BN-KL. Close to BN-KL, however, there is evidence that this trend is reversed.

scholarly journals Molecular gas in the Small Magellanic Cloud

1991 ◽  
Vol 148 ◽  
pp. 429-430
Author(s):  
Monica Rubio
Keyword(s):  
Molecular Hydrogen ◽  
Molecular Clouds ◽  
Column Density ◽  
Angular Resolution ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Molecular Gas ◽  
Small Magellanic Cloud ◽  
Hydrogen Column Density ◽  
Co Emission

We summarize the results of observations of molecular gas from the Small Magellanic Cloud (SMC) made with low angular resolution (8'.8). These observations show that the CO emission is weak (TA˜ 0.04K) and that the CO luminosities of the Clouds are low compared to those of Galactic molecular clouds. The factor to convert the CO luminosity to molecular hydrogen column density for the SMC is ˜20 and three times larger than those derived for clouds in our Galaxy and in the Large Magellanic Cloud (LMC) respectively. In addition, we present preliminary results of high resolution (40″) observations of SMC molecular clouds made with the SEST telescope.

scholarly journals Small Scale Structure in Nearby Molecular Gas

1997 ◽  
Vol 166 ◽  
pp. 251-260 ◽  
Author(s):  
Edith Falgarone
Keyword(s):  
Molecular Clouds ◽  
Column Density ◽  
Angular Resolution ◽  
Ambient Pressure ◽  
Solar Neighborhood ◽  
Small Scale ◽  
High Angular Resolution ◽  
Molecular Gas ◽  
Hierarchy Of Structures ◽  
Co Emission

AbstractRecent observations at high angular resolution of molecular clouds of low column density have revealed the presence of a conspicuous net of small scale filamentary structures, visible in the 12CO rotational lines only. In addition, the existence of unresolved structure at scales as small as ~ 200 AU in space and/or velocity space is inferred from the spectral properties of the 12CO and 13CO emission. The resolved structures are part of the hierarchy of structures observed in molecular gas in the Solar Neighborhood and appear as non self-gravitating elements confined by an ambient pressure P0/kB ~ 3 × 104cm−3 K. We show why these structures might have their origin in the intermittent structures of turbulence in which viscous dissipation is concentrated in space and time.

scholarly journals Molecular gas in the Herschel-selected strongly lensed submillimeter galaxies at z ~ 2–4 as probed by multi-J CO lines

2017 ◽  
Vol 608 ◽  
pp. A144 ◽  
Author(s):  
C. Yang ◽  
A. Omont ◽  
A. Beelen ◽  
Y. Gao ◽  
P. van der Werf ◽  
...  
Keyword(s):  
Star Formation ◽  
High Redshift ◽  
Line Emission ◽  
Far Infrared ◽  
Molecular Gas ◽  
Kinetic Temperature ◽  
Large Area ◽  
Line Energy ◽  
Submillimeter Galaxies ◽  
Dust Mass

We present the IRAM-30 m observations of multiple-J CO (Jup mostly from 3 up to 8) and [C I](3P2 → 3P1) ([C I](2–1) hereafter) line emission in a sample of redshift ~2–4 submillimeter galaxies (SMGs). These SMGs are selected among the brightest-lensed galaxies discovered in the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS). Forty-seven CO lines and 7 [C I](2–1) lines have been detected in 15 lensed SMGs. A non-negligible effect of differential lensing is found for the CO emission lines, which could have caused significant underestimations of the linewidths, and hence of the dynamical masses. The CO spectral line energy distributions (SLEDs), peaking around Jup ~ 5–7, are found to be similar to those of the local starburst-dominated ultra-luminous infrared galaxies and of the previously studied SMGs. After correcting for lensing amplification, we derived the global properties of the bulk of molecular gas in the SMGs using non-LTE radiative transfer modelling, such as the molecular gas density nH2 ~ 102.5–104.1 cm-3 and the kinetic temperature Tk  ~ 20–750 K. The gas thermal pressure Pth ranging from~105 K cm-3 to 106 K cm-3 is found to be correlated with star formation efficiency. Further decomposing the CO SLEDs into two excitation components, we find a low-excitation component with nH2 ~ 102.8–104.6 cm-3 and Tk  ~ 20–30 K, which is less correlated with star formation, and a high-excitation one (nH2 ~ 102.7–104.2 cm-3, Tk  ~ 60–400 K) which is tightly related to the on-going star-forming activity. Additionally, tight linear correlations between the far-infrared and CO line luminosities have been confirmed for the Jup ≥ 5 CO lines of these SMGs, implying that these CO lines are good tracers of star formation. The [C I](2–1) lines follow the tight linear correlation between the luminosities of the [C I](2–1) and the CO(1–0) line found in local starbursts, indicating that [C I] lines could serve as good total molecular gas mass tracers for high-redshift SMGs as well. The total mass of the molecular gas reservoir, (1–30) × 1010M⊙, derived based on the CO(3–2) fluxes and αCO(1–0) = 0.8 M⊙ ( K km s-1 pc2)-1, suggests a typical molecular gas depletion time tdep ~ 20–100 Myr and a gas to dust mass ratio δGDR ~ 30–100 with ~20%–60% uncertainty for the SMGs. The ratio between CO line luminosity and the dust mass L′CO/Mdust appears to be slowly increasing with redshift for high-redshift SMGs, which need to be further confirmed by a more complete SMG sample at various redshifts. Finally, through comparing the linewidth of CO and H2O lines, we find that they agree well in almost all our SMGs, confirming that the emitting regions of the CO and H2O lines are co-spatially located.

scholarly journals The Molecular Outflow and CO Bullets in HH111

1997 ◽  
Vol 182 ◽  
pp. 141-152 ◽  
Author(s):  
J. Cernicharo ◽  
R. Neri ◽  
Bo Reipurth
Keyword(s):  
High Velocity ◽  
Angular Resolution ◽  
High Angular Resolution ◽  
Molecular Gas ◽  
Kinetic Temperature ◽  
Low Velocity ◽  
Molecular Outflow ◽  
Hh Objects ◽  
Physical Phenomena ◽  
First Time

We present high angular resolution observations of the molecular outflow associated with the optical jet and HH objects of the HH111 system. Interferometric observations in the CO J =2–1 and J =1–0 lines of the high velocity bullets associated with HH111 are presented for the first time. The molecular gas in these high velocity clumps has a moderate kinetic temperature and a mass of a few 10–4 M⊙ per bullet. We favor the view that HH jets and CO bullets, which represent different manifestations of the same physical phenomena, are driving the low-velocity molecular outflow.

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 Warm Gas and Spatial Variations of Molecular Excitation in the Nuclear Region of IC342

1989 ◽  
Vol 8 ◽  
pp. 589-590
Author(s):  
A. Eckart ◽  
D. Downes ◽  
R. Genzel ◽  
A.I. Harris ◽  
D.T. Jaffe ◽  
...  
Keyword(s):  
Line Emission ◽  
Molecular Gas ◽  
Kinetic Temperature ◽  
Nuclear Region ◽  
Model Calculations ◽  
Physical Conditions ◽  
North East ◽  
The Galaxy ◽  
Molecular Excitation ◽  
North And South

Using the IRAM 30m millimeter radio telescope we mapped the line emission of the J=1-0 and J=2-1 transitions of 12C0, 13C0, and C180 in the nuclear region of the spiral galaxy IC342. This study demonstrates the value of multi line studies to investigate the neutral interstellar medium in extragalactic sources. Our observations as well as calculations of simple models of CO excitation and radiative transport show that the molecular gas in the nucleus is warm and that physical conditions vary with position in the galaxy. The molecular gas in the central kiloparsec of IC342 has a kinetic temperature of at least 30K and a molecular hydrogen density of about 3xl03 cm”3. At distances more than 500pc north and south of the center the kinetic temperature is significantly less (≥13K). About 500 pc north east of the center we find evidence for optically thin CO emission originating in a component of warm gas with a temperature of at least 40 K. Our model calculations result in conversion factors between the H2 column density and the 12CO (1-0) line intensity close to the value of 3–4×1020 cm-2/K km s-1 derived for molecular clouds in the Galaxy. The molecular mass contained in the central two kpc of IC342 is of the order of 2×108 M⊙.

scholarly journals Correlation of gas dynamics and dust in the evolved filament G82.65-02.00

2017 ◽  
Vol 608 ◽  
pp. A21 ◽  
Author(s):  
M. Saajasto ◽  
M. Juvela ◽  
K. Dobashi ◽  
T. Shimoikura ◽  
I. Ristorcelli ◽  
...  
Keyword(s):  
Column Density ◽  
Velocity Structure ◽  
Accretion Rate ◽  
Initial Conditions ◽  
Dust Emission ◽  
Line Emission ◽  
Star Forming ◽  
Virial Mass ◽  
The Masses ◽  
Main Filament

Context. The combination of line and continuum observations can provide vital insight into the formation and fragmentation of filaments and the initial conditions for star formation. We have carried out line observations to map the kinematics of an evolved, actively star forming filament G82.65-2.00. The filament was first identified from the Planck data as a region of particularly cold dust emission and was mapped at 100–500 μm as a part of the Herschel key program Galactic Cold Cores. The Herschel observations cover the central part of the filament, corresponding to a filament length of ~ 12 pc at the assumed distance of 620 pc. Aims. CO observations show that the filament has an intriguing velocity field with several velocity components around the filament. In this paper, we study the velocity structure in detail, to quantify possible mass accretion rate onto the filament, and study the masses of the cold cores located in the filament. Methods. We have carried out line observations of several molecules, including CO isotopologues, HCO+, HCN, and CS with the Osaka 1.85 m telescope and the Nobeyama 45 m telescope. The spectral line data are used to derive velocity and column density information. Results. The observations reveal several velocity components in the field, with strongest line emission concentrated to velocity range ~[3,5] km s-1. The column density of molecular hydrogen along the filament varies from 1.0 to 2.3 × 1022cm2. We have examined six cold clumps from the central part of the filament. The clumps have masses in the range 10−20M⊙ (~ 70 M⊙ in total) and are close to or above the virial mass. Furthermore, the main filament is heavily fragmented and most of the substructures have a mass lower than or close to the virial mass, suggesting that the filament is dispersing as a whole. Position-velocity maps of 12CO and 13CO lines indicate that at least one of the striations is kinematically connected to two of the clumps, potentially indicating mass accretion from the striation onto the main filament. We tentatively estimate the accretion rate to be Ṁ = 2.23 × 10-6M⊙/ yr. Conclusions. Our line observations have revealed two or possibly three velocity components connected to the filament G82.65-2.00 and putative signs of mass accretion onto the filament. The line observations combined with Herschel and WISE maps suggest a possible collision between two cloud components.

scholarly journals High-J CO emission spatial distribution and excitation in the Orion Bar

2018 ◽  
Vol 617 ◽  
pp. A77 ◽  
Author(s):  
A. Parikka ◽  
E. Habart ◽  
J. Bernard-Salas ◽  
M. Köhler ◽  
A. Abergel
Keyword(s):  
Angular Resolution ◽  
Volume Density ◽  
High Angular Resolution ◽  
Molecular Gas ◽  
Vibrationally Excited ◽  
Physical Conditions ◽  
Ionization Fronts ◽  
Polycyclic Aromatic ◽  
Imaging Receiver ◽  
Co Emission

Context. With Herschel, we can for the first time observe a wealth of high-J CO lines in the interstellar medium with a high angular resolution. These lines are specifically useful for tracing the warm and dense gas and are therefore very appropriate for a study of strongly irradiated dense photodissocation regions (PDRs). Aims. We characterize the morphology of CO J = 19–18 emission and study the high-J CO excitation in a highly UV-irradiated prototypical PDR, the Orion Bar. Methods. We used fully sampled maps of CO J = 19–18 emission with the Photoconductor Array Camera and Spectrometer (PACS) on board the Herschel Space Observatory over an area of ~110′′ × 110′′ with an angular resolution of 9′′. We studied the morphology of this high-J CO line in the Orion Bar and in the region in front and behind the Bar, and compared it with lower-J lines of CO from J = 5–4 to J = 13–12 and 13CO from J = 5–4 to J = 11–10 emission observed with the Herschel Spectral and Photometric Imaging Receiver (SPIRE). In addition, we compared the high-J CO to polycyclic aromatic hydrocarbon (PAH) emission and vibrationally excited H2. We used the CO and 13CO observations and the RADEX model to derive the physical conditions in the warm molecular gas layers. Results. The CO J = 19–18 line is detected unambiguously everywhere in the observed region, in the Bar, and in front and behind of it. In the Bar, the most striking features are several knots of enhanced emission that probably result from column and/or volume density enhancements. The corresponding structures are most likely even smaller than what PACS is able to resolve. The high-J CO line mostly arises from the warm edge of the Orion Bar PDR, while the lower-J lines arise from a colder region farther inside the molecular cloud. Even if it is slightly shifted farther into the PDR, the high-J CO emission peaks are very close to the H/H2 dissociation front, as traced by the peaks of H2 vibrational emission. Our results also suggest that the high-J CO emitting gas is mainly excited by photoelectric heating. The CO J = 19–18/J = 12–11 line intensity ratio peaks in front of the CO J = 19–18 emission between the dissociation and ionization fronts, where the PAH emission also peak. A warm or hot molecular gas could thus be present in the atomic region where the intense UV radiation is mostly unshielded. In agreement with recent ALMA detections, low column densities of hot molecular gas seem to exist between the ionization and dissociation fronts. As found in other studies, the best fit with RADEX modeling for beam-averaged physical conditions is for a density of 106 cm−3 and a high thermal pressure (P∕k = nH × T) of ~1–2 × 108 K cm−3. Conclusions. The high-J CO emission is concentrated close to the dissociation front in the Orion Bar. Hot CO may also lie in the atomic PDR between the ionization and dissociation fronts, which is consistent with the dynamical and photoevaporation effects.

scholarly journals Molecular gas and dust emission in a z = 3.63 strongly lensed starburst merger at sub-kiloparsec scales

2019 ◽  
Vol 15 (S352) ◽  
pp. 297-299
Author(s):  
C. Yang ◽  
R. Gavazzi ◽  
A. Beelen ◽  
P. Cox ◽  
A. Omont ◽  
...  
Keyword(s):  
Dust Emission ◽  
Line Emission ◽  
Rotating Disk ◽  
Molecular Gas ◽  
Lens Model ◽  
Infrared Galaxies ◽  
Gas Reservoir ◽  
Luminous Infrared Galaxies ◽  
Major Merger ◽  
Projected Distance

AbstractWe present 0.″2–0.″4 resolution ALMA images of the submillimeter dust continuum and the CO, H2O, and H2O+ line emission in a z = 3.63 strongly lensed dusty starburst. We construct the lens model for the system with an MCMC technique. While the average magnification for the dust continuum is about 11, the magnification of the line emission varies from 5 to 22 across the source, resolving the source down to sub-kpc scales. The ISM content reveals that it is a pre-coalescence major merger of two ultra-luminous infrared galaxies, both with a large amount of molecular gas reservoir. The approaching galaxy in the south shows no apparent kinematic structure with a half-light radius of 0.4 kpc, while the preceding one resembles a 1.2 kpc rotating disk, separated by a projected distance of 1.3 kpc. The distribution of dust and gas emission suggests a large amount of cold ISM concentrated in the interacting region.

scholarly journals Tracing the cold molecular gas reservoir through dust emission in the SMC

2008 ◽  
Vol 4 (S256) ◽  
pp. 148-153
Author(s):  
Caroline Bot ◽  
Mónica Rubio ◽  
François Boulanger ◽  
Marcus Albrecht ◽  
Frank Bertoldi ◽  
...  
Keyword(s):  
Molecular Clouds ◽  
Virial Theorem ◽  
Spectral Energy Distribution ◽  
Dust Emission ◽  
Spectral Energy ◽  
Molecular Gas ◽  
Giant Molecular Clouds ◽  
Gas Reservoir ◽  
Co Emission ◽  
Co Observations

AbstractThe amount of molecular gas is a key for understanding the future star formation in a galaxy. However, this quantity is difficult to infer as the cold H2 is almost impossible to observe and, especially at low metallicities, CO only traces part of the clouds, keeping large envelopes of H2 hidden from observations. In this context, millimeter dust emission tracing the cold and dense regions can be used as a tracer to unveil the total molecular gas masses. I present studies of a sample of giant molecular clouds in the Small Magellanic Cloud. These clouds have been observed in the millimeter and sub-millimeter continuum of dust emission: with SIMBA/SEST at 1.2 mm and the new LABOCA bolometer on APEX at 870 μm. Combining these with radio data for each cloud, the spectral energy distribution of dust emission are obtained and gas masses are inferred. The molecular cloud masses are found to be systematically larger than the virial masses deduced from CO emission. Therefore, the molecular gas mass in the SMC has been underestimated by CO observations, even through the dynamical masses. This result confirms what was previously observed by Bot et al. (2007). We discuss possible interpretations of the mass discrepancy observed: in the giant molecular clouds of the SMC, part of cloud's support against gravity could be given by a magnetic field. Alternatively, the inclusion of surface terms in the virial theorem for turbulent clouds could reproduce the observed results and the giant molecular clouds could be transient structures.

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