The Fractal Dimension of Star-Forming Regions at Different Spatial Scales in M33

Sánchez, Néstor; Añez, Neyda; Alfaro, E. J.; Odekon, Mary Crone

doi:10.1088/0004-637x/720/1/541

Cited by 42 publications

(24 citation statements)

References 61 publications

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“…The central part of the cloud contains a dense region with peak density 2 10 cm 4 3´-. The fractal dimension is in accordance to the clumpiness factor observed in evolved Galactic H II regions (e.g., Sánchez et al 2010;Walch et al 2015). Incontrast,the fractal dimension is higher for diffuse clouds ( 2.8 3.0 ~-), meaning that they are more uniform (Walch et al 2015).…”

Section: Density Distributionsupporting

confidence: 79%

Cosmic-ray Induced Destruction of CO in Star-forming Galaxies

Bisbas

Dishoeck

Papadopoulos

et al. 2017

ApJ

131

147

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We explore the effects of the expected higher cosmic ray (CR) ionization rates CR z on the abundances of carbon monoxide (CO), atomic carbon (C), and ionized carbon (C + ) in the H 2 clouds of star-forming galaxies. The study of Bisbas et al. is expanded by(a) using realistic inhomogeneous giant molecular cloud (GMC) structures, (b) a detailed chemical analysis behind the CR-induced destruction of CO, and (c) exploring the thermal state of CRirradiated molecular gas. CRs permeating the interstellar medium with 10 Galactic CR  z´( ) are found to significantly reduce the [CO]/[H 2 ] abundance ratios throughout the mass of a GMC. CO rotational line imaging will then show much clumpier structures than the actual ones. For 100 CR  z´(Galactic) this bias becomes severe, limiting the usefulnessof CO lines for recovering structural and dynamical characteristics of H 2 -rich galaxies throughout the universe, including many of the so-called main-sequence galaxies where the bulk of cosmic star formation occurs. Both C + and C abundances increase with rising CR

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Section: Density Distributionsupporting

confidence: 79%

Cosmic-ray Induced Destruction of CO in Star-forming Galaxies

Bisbas

Dishoeck

Papadopoulos

et al. 2017

ApJ

131

147

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“…All maps have been deprojected, with the adopted inclination of 56 • and position angle of 22.5 • , before Fourier analysis. The data analyzed in the present work are more appropriate than earlier data (Elmegreen et al 2003b;Odekon 2008;Sanchez et al 2010) to study the power spectra and the structure of the interstellar medium, since they refer directly to the gas and dust in M 33, and they have the dynamical range (from 40 pc to 20 kpc) and spatial resolution to reveal the thickness of the gas layer. The gas and dust emission trace directly the collisional material, with no intervening and perturbing emission (like galactic stars).…”

Section: Observational Datamentioning

confidence: 99%

“…This scale does not change much with the age of the stellar population considered, although the slope is steeper for the bluest and youngest stars. Sanchez et al (2010) investigate all the young components in M 33, including young stars, HII regions and molecular clouds, and also find a clear transition region, but in the range 0.5−1 kpc. That different results are obtained for the same galaxies calls for new studies to clarify the situation.…”

Section: Introductionmentioning

confidence: 95%

Dust and gas power spectrum in M 33 (HERM33ES)

Combes

Boquien

Krämer

et al. 2012

A&A

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Power spectra of deprojected images of late-type galaxies in gas or dust emission are very useful diagnostics of the dynamics and stability of their interstellar medium. Previous studies have shown that the power spectra can be approximated as two power laws, a shallow one on large scales (larger than 500 pc) and a steeper one on small scales, with the break between the two corresponding to the line-of-sight thickness of the galaxy disk. The break separates the 3D behavior of the interstellar medium on small scales, controlled by star formation and feedback, from the 2D behavior on large scales, driven by density waves in the disk. The break between these two regimes depends on the thickness of the plane, which is determined by the natural self-gravitating scale of the interstellar medium. We present a thorough analysis of the power spectra of the dust and gas emission at several wavelengths in the nearby galaxy M 33. In particular, we use the recently obtained images at five wavelengths by PACS and SPIRE onboard Herschel. The wide dynamical range (2-3 dex in scale) of most images allows us to clearly determine the change in slopes from −1.5 to −4, with some variations with wavelength. The break scale increases with wavelength from 100 pc at 24 and 100 μm to 350 pc at 500 μm, suggesting that the cool dust lies in a thicker disk than the warm dust, perhaps because of star formation that is more confined to the plane. The slope on small scales tends to be steeper at longer wavelength, meaning that the warmer dust is more concentrated in clumps. Numerical simulations of an isolated late-type galaxy, rich in gas and with no bulge, such as M 33, are carried out to better interpret these observed results. Varying the star formation and feedback parameters, it is possible to obtain a range of power spectra, with two power-law slopes and breaks, that nicely bracket the data. The small-scale power-law does indeed reflect the 3D behavior of the gas layer, steepening strongly while the feedback smoothes the structures by increasing the gas turbulence. M 33 appears to correspond to a fiducial model with an SFR of ∼0.7 M /yr, with 10% supernovae energy coupled to the gas kinematics.

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“…When two galaxy disks collide nearly face-on at high velocity, we expect widespread collisions between diffuse atomic clouds, which have a large covering factor in galaxy disks (Leroy et al 2008;Sánchez et al 2010). In the collision, dense molecular clouds in one galaxy will ram through the more diffuse atomic gas of the second galaxy.…”

Section: Introductionmentioning

confidence: 99%

DETECTION OF POWERFUL MID-IR H₂EMISSION IN THE BRIDGE BETWEEN THE TAFFY GALAXIES

Peterson

Appleton

Hélou

et al. 2012

ApJ

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We report the detection of strong, resolved emission from warm H 2 in the Taffy galaxies and bridge. Relative to the continuum and faint polyclic aromatic hydrocarbon (PAH) emission, the H 2 emission is the strongest in the connecting bridge, approaching L(H 2 )/L(PAH 8 μm) = 0.1 between the two galaxies, where the purely rotational lines of H 2 dominate the mid-infrared spectrum in a way very reminiscent of the group-wide shock in the interacting group Stephan's Quintet (SQ). The surface brightness in the 0-0 S(0) and S(1) H 2 lines in the bridge is more than twice that observed at the center of the SQ shock. We observe a warm H 2 mass of 4.2 × 10 8 M in the bridge, but taking into account the unobserved bridge area, the total warm mass is likely to be twice this value. We use excitation diagrams to characterize the warm molecular gas, finding an average surface mass of ∼5 × 10 6 M kpcand typical excitation temperatures of 150-175 K. H 2 emission is also seen in the galaxy disks, although there the emission is more consistent with normal star-forming galaxies. We investigate several possible heating mechanisms for the bridge gas but favor the conversion of kinetic energy from the head-on collision via turbulence and shocks as the main heating source. Since the cooling time for the warm H 2 is short (∼5000 yr), shocks must be permeating the molecular gas in the bridge region in order to continue heating the H 2 .

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The Fractal Dimension of Star-Forming Regions at Different Spatial Scales in M33

Cited by 42 publications

References 61 publications

Cosmic-ray Induced Destruction of CO in Star-forming Galaxies

Cosmic-ray Induced Destruction of CO in Star-forming Galaxies

Dust and gas power spectrum in M 33 (HERM33ES)

DETECTION OF POWERFUL MID-IR H₂EMISSION IN THE BRIDGE BETWEEN THE TAFFY GALAXIES

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The Fractal Dimension of Star-Forming Regions at Different Spatial Scales in M33

Cited by 42 publications

References 61 publications

Cosmic-ray Induced Destruction of CO in Star-forming Galaxies

Cosmic-ray Induced Destruction of CO in Star-forming Galaxies

Dust and gas power spectrum in M 33 (HERM33ES)

DETECTION OF POWERFUL MID-IR H2EMISSION IN THE BRIDGE BETWEEN THE TAFFY GALAXIES

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Product

Resources

About

DETECTION OF POWERFUL MID-IR H₂EMISSION IN THE BRIDGE BETWEEN THE TAFFY GALAXIES