The Relation Between Gas and Dust in the Taurus Molecular Cloud

Pineda, J. L.; Goldsmith, Paul F.; Chapman, Nicholas; Snell, R. L.; Li, Di; Cambrésy, L.; Brunt, Chris

doi:10.1088/0004-637x/721/1/686

Cited by 250 publications

(376 citation statements)

References 67 publications

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“…Our simulation volume is large enough to contain Taurus-like structures. The velocity dispersion at the earlier time shown from our simulation is the closest to what is seen in Taurus, consistent with the view that the Taurus area is still relatively young (e.g., Hartmann et al 2001;Luhman et al 2003Luhman et al , 2007Pineda et al 2010).…”

Section: Analysis Of the Profilessupporting

confidence: 87%

Molecular cloud formation as seen in synthetic H i and molecular gas observations

Heiner¹,

Vázquez‐Semadeni²,

Ballesteros-Paredes³

2015

Mon. Not. R. Astron. Soc.

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We present synthetic Hi and CO observations of a numerical simulation of decaying turbulence in the thermally bistable neutral medium. We first present the simulation, which produces a clumpy medium, with clouds initially consisting of clustered clumps. Self-gravity causes these clump clusters to merge and form more homogeneous dense clouds. We apply a simple radiative transfer algorithm, throwing rays in many directions from each cell, and defining every cell with A v > 1 as molecular. We then produce maps of Hi, CO-free molecular gas, and CO, and investigate the following aspects: i) The spatial distribution of the warm, cold, and molecular gas, finding the well-known layered structure, with molecular gas being surrounded by cold Hi and this in turn being surrounded by warm Hi. ii) The velocity of the various components, finding that the atomic gas is generally flowing towards the molecular gas, and that this motion is reflected in the frequently observed bimodal shape of the Hi profiles. This conclusion is, however, tentative, because we do not include feedback that may produce Hi gas receding from molecular regions. iii) The production of Hi self-absorption (HISA) profiles, and the correlation of HISA with molecular gas. In particular, we test the suggestion of using the second derivative of the brightness temperature Hi profile to trace HISA and molecular gas, finding significant limitations. On a scale of several parsecs, some agreement is obtained between this technique and actual HISA, as well as a correlation between HISA and the molecular gas column density. This correlation, however, quickly deteriorates towards sub-parsec scales. iv) The column density PDFs of the actual Hi gas and those recovered from the Hi line profiles, finding that the latter have a cutoff at column densities where the gas becomes optically thick, thus missing the contribution from the HISA-producing gas. We also find that the powerlaw tail typical of gravitational contraction is only observed in the molecular gas, and that, before the power-law tail develops in the total gas density PDF, no CO is yet present, reinforcing the notion that gravitational contraction is needed to produce this component.

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Section: Analysis Of the Profilessupporting

confidence: 87%

Molecular cloud formation as seen in synthetic H i and molecular gas observations

Heiner¹,

Vázquez‐Semadeni²,

Ballesteros-Paredes³

2015

Mon. Not. R. Astron. Soc.

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“…Figure 1(e) shows the excitation temperature map derived from the following equation with the previous assumption (1) and the beam filling factor of one (e.g., Pineda et al 2010;Kong et al 2015) is the peak intensity of 12 CO ( J = 1-0) in units of K from the above fitting, =…”

Section: Herschel Column Density and Dust Temperature Mapsmentioning

confidence: 99%

“…Nevertheless, the X-factor can vary by a factor of ∼100 in different regions, because 12 CO ( J = 1-0) is often optically thick (Lee et al 2014). For example, Pineda et al (2010) measured X-factor ∼(1.6-12) × 10 20 cm −2 K −1 km −1 s in the Taurus molecular cloud, Lee et al (2014) measured X-factor ∼3 × 10 19 cm −2 K −1 km −1 s in the Perseus molecular cloud, and Kong et al (2015) measured X-factor ∼2.53 × 10 20 cm −2 K −1 km −1 s in the southeastern part of the California molecular cloud. These discrepancies are also found in ISM numerical simulations, which show that the X-factor is likely dependent on extinction, volume density, temperature, metallicity, turbulence, star formation feedback, and so on (Shetty et al 2011a(Shetty et al , 2011bLee et al 2014;Clark & Glover 2015).…”

Section: Co-to-h 2 Conversion Factor Across the L 1551 Molecular Cloudmentioning

confidence: 99%

The Intrinsic Abundance Ratio and X-Factor of Co Isotopologues in L 1551 Shielded From Fuv Photodissociation

Lin

Shimajiri

Hara

et al. 2016

ApJ

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We investigate the intrinsic abundance ratio of 13 CO to C 18 O and the X-factor in L 1551 using the Nobeyama Radio Observatory (NRO) 45 m telescope. L 1551 is chosen because it is relatively isolated in the Taurus molecular cloud shielded from FUV photons, providing an ideal environment for studying the target properties. Our observations cover~¢´¢ 40 40 with a resolution of~ 30 , which make up maps with the highest spatial dynamical range to date. We derive the X Xvalue on the sub-parsec scales in the range of ∼3-27 with a mean value of 8.0 ± 2.8. Comparing to the visual extinction map derived from the Herschel observations, we found that the abundance ratio reaches its maximum at low A V (i.e., A V ∼ 1-4 mag), and decreases to the typical solar system value of 5.5 inside L 1551 MC. The high X Xvalue at the boundary of the cloud is most likely due to the selective FUV photodissociation of C 18 O. This is in contrast with Orion-A where internal OB stars keep the abundance ratio at a high level, greater than ∼10. In addition, we explore the variation of the X-factor, because it is an uncertain, but widely used, quantity in extragalactic studies. We found that the X-factor µN H 1.0 2 , which is consistent with previous simulations. Excluding the high density region, the average X-factor is similar to the Milky Way average value.

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“…We applied the error beam scaling factor recently proposed by Pineda et al (2010), so that the intensities of the CfA and FCRAO surveys of the 12 CO emission line are compatible. The statistical noise per pixel (with pixel size of 0.33 ) of the velocity-integrated intensity maps is about 0.4 K km s −1 for the 13 CO line.…”

Section: Ancillary Datamentioning

confidence: 99%

“…The column density can also be traced from the nearinfrared (NIR) extinction using the 2MASS point source catalogue (e.g., Dobashi et al 2005;Pineda et al 2010). For comparison with HFI data, we used the extinction map of the central part of the Taurus molecular cloud recently created by Pineda et al (2010) and shown in Fig.…”

Section: Ancillary Datamentioning

confidence: 99%

Planckearly results. XXV. Thermal dust in nearby molecular clouds

Abergel

Ade

Aghanim

et al. 2011

A&A

186

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Planck allows unbiased mapping of Galactic sub-millimetre and millimetre emission from the most diffuse regions to the densest parts of molecular clouds. We present an early analysis of the Taurus molecular complex, on line-of-sight-averaged data and without component separation. The emission spectrum measured by Planck and IRAS can be fitted pixel by pixel using a single modified blackbody. Some systematic residuals are detected at 353 GHz and 143 GHz, with amplitudes around −7% and +13%, respectively, indicating that the measured spectra are likely more complex than a simple modified blackbody. Significant positive residuals are also detected in the molecular regions and in the 217 GHz and 100 GHz bands, mainly caused by the contribution of the J = 2 → 1 and J = 1 → 0 12 CO and 13 CO emission lines. We derive maps of the dust temperature T , the dust spectral emissivity index β, and the dust optical depth at 250 μm τ 250 . The temperature map illustrates the cooling of the dust particles in thermal equilibrium with the incident radiation field, from 16−17 K in the diffuse regions to 13−14 K in the dense parts. The distribution of spectral indices is centred at 1.78, with a standard deviation of 0.08 and a systematic error of 0.07. We detect a significant T − β anti-correlation. The dust optical depth map reveals the spatial distribution of the column density of the molecular complex from the densest molecular regions to the faint diffuse regions. We use near-infrared extinction and H i data at 21-cm to perform a quantitative analysis of the spatial variations of the measured dust optical depth at 250 μm per hydrogen atom τ 250 /N H . We report an increase of τ 250 /N H by a factor of about 2 between the atomic phase and the molecular phase, which has a strong impact on the equilibrium temperature of the dust particles.

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The Relation Between Gas and Dust in the Taurus Molecular Cloud

Cited by 250 publications

References 67 publications

Molecular cloud formation as seen in synthetic H i and molecular gas observations

Molecular cloud formation as seen in synthetic H i and molecular gas observations

The Intrinsic Abundance Ratio and X-Factor of Co Isotopologues in L 1551 Shielded From Fuv Photodissociation

Planckearly results. XXV. Thermal dust in nearby molecular clouds

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