High-fidelity view of the structure and fragmentation of the high-mass, filamentary IRDC G11.11-0.12

Star formation in molecular clouds is intimately linked to their internal mass distribution. We present an unprecedentedly detailed analysis of the column density structure of a high-mass, filamentary molecular cloud, namely IRDC G11.11-0.12 (G11). We use two novel column density mapping techniques: high-resolution (FWHM=2", or ~0.035 pc) dust extinction mapping in near- and mid-infrared, and dust emission mapping with the Herschel satellite. These two completely independent techniques yield a strikingly good agreement, highlighting their complementarity and robustness. We first analyze the dense gas mass fraction and linear mass density of G11. We show that G11 has a top heavy mass distribution and has a linear mass density (M_l ~ 600 Msun pc^{-1}) that greatly exceeds the critical value of a self-gravitating, non-turbulent cylinder. These properties make G11 analogous to the Orion A cloud, despite its low star-forming activity. This suggests that the amount of dense gas in molecular clouds is more closely connected to environmental parameters or global processes than to the star-forming efficiency of the cloud. We then examine hierarchical fragmentation in G11 over a wide range of size-scales and densities. We show that at scales 0.5 pc > l > 8 pc, the fragmentation of G11 is in agreement with that of a self-gravitating cylinder. At scales smaller than l < 0.5 pc, the results agree better with spherical Jeans' fragmentation. One possible explanation for the change in fragmentation characteristics is the size-scale-dependent collapse time-scale that results from the finite size of real molecular clouds: at scales l < 0.5 pc, fragmentation becomes sufficiently rapid to be unaffected by global instabilities.Comment: 8 pages, 8 figures, accepted to A&

Relationship between the column density distribution and evolutionary class of molecular clouds as viewed by ATLASGAL

We present the first study of the relationship between the column density distribution of molecular clouds within nearby Galactic spiral arms and their evolutionary status as measured from their stellar content. We analyze a sample of 195 molecular clouds located at distances below 5.5 kpc, identified from the ATLASGAL 870 micron data. We define three evolutionary classes within this sample: starless clumps, star-forming clouds with associated young stellar objects, and clouds associated with HII regions. We find that the N(H2) probability density functions (N-PDFs) of these three classes of objects are clearly different: the N-PDFs of starless clumps are narrowest and close to log-normal in shape, while star-forming clouds and HII regions exhibit a power-law shape over a wide range of column densities and log-normal-like components only at low column densities. We use the N-PDFs to estimate the evolutionary time-scales of the three classes of objects based on a simple analytic model from literature. Finally, we show that the integral of the N-PDFs, the dense gas mass fraction, depends on the total mass of the regions as measured by ATLASGAL: more massive clouds contain greater relative amounts of dense gas across all evolutionary classes.Comment: Accepted for publication in A&A (25th June 15) 23 pages, 12 figures. Additional appendix figures will appear in the journal version of this pape

Baryogenesis in the MSSM, nMSSM and NMSSM

We compare electroweak baryogenesis in the MSSM, nMSSM and NMSSM. We comment on the different sources of CP violation, the phase transition and constraints from EDM measurements.Comment: 6 pages, 4 figures. To appear in the proceedings of the 7th Conference on Strong and Electroweak Matter (SEWM06), Brookhaven National Laboratory, May 10-13, 200

Connection between dense gas mass fraction, turbulence driving, and star formation efficiency of molecular clouds

We examine the physical parameters that affect the accumulation of gas in molecular clouds to high column densities where the formation of stars takes place. In particular, we analyze the dense gas mass fraction (DGMF) in a set of self-gravitating, isothermal, magnetohydrodynamic turbulence simulations that include sink particles to model star formation. We find that the simulations predict close to exponential DGMFs over the column density range N(H 2) = 3-25 × 1021 cm-2 that can be easily probed via, e.g., dust extinction measurements. The exponential slopes correlate with the type of turbulence driving and also with the star formation efficiency. They are almost uncorrelated with the sonic Mach number and magnetic-field strength. The slopes at early stages of cloud evolution are steeper than at the later stages. A comparison of these predictions with observations shows that only simulations with relatively noncompressive driving (b ≠0.4) agree with the DGMFs of nearby molecular clouds. Massive infrared dark clouds can show DGMFs that agree with more compressive driving. The DGMFs of molecular clouds can be significantly affected by how compressive the turbulence is on average. Variations in the level of compression can cause scatter to the DGMF slopes, and some variation is indeed necessary to explain the spread of the observed DGMF slopes. The observed DGMF slopes can also be affected by the clouds' star formation activities and statistical cloud-to-cloud variations

Conformal Window of Gauge Theories with Four-Fermion Interactions and Ideal Walking

We investigate the effects of four-fermion interactions on the phase diagram of strongly interacting theories for any representation as function of the number of colors and flavors. We show that the conformal window, for any representation, shrinks with respect to the case in which the four-fermion interactions are neglected. The anomalous dimension of the mass increases beyond the unity value at the lower boundary of the new conformal window. We plot the new phase diagram which can be used, together with the information about the anomalous dimension, to propose ideal models of walking technicolor. We discover that when the extended technicolor sector, responsible for giving masses to the standard model fermions, is sufficiently strongly coupled the technicolor theory, in isolation, must have an infrared fixed point for the full model to be phenomenologically viable. Using the new phase diagram we show that the simplest one family and minimal walking technicolor models are the archetypes of models of dynamical electroweak symmetry breaking. Our predictions can be verified via first principle lattice simulations.Comment: RevTeX4, 22 pages, 16 figure

Uncovering the kiloparsec-scale stellar ring of NGC5128

We reveal the stellar light emerging from the kiloparsec-scale, ring-like structure of the NGC5128 (Centaurus A) galaxy in unprecedented detail. We use arcsecond-scale resolution near infrared images to create a "dust-free" view of the central region of the galaxy, which we then use to quantify the shape of the revealed structure. At the resolution of the data, the structure contains several hundreds of discreet, point-like or slightly elongated sources. Typical extinction corrected surface brightness of the structure is K_S = 16.5 mag/arcsec^2, and we estimate the total near infrared luminosity of the structure to be M = -21 mag. We use diffraction limited (FWHM resolution of ~ 0.1", or 1.6 pc) near infrared data taken with the NACO instrument on VLT to show that the structure decomposes into thousands of separate, mostly point-like sources. According to the tentative photometry, the most luminous sources have M_K = -12 mag, naming them red supergiants or relatively low-mass star clusters. We also discuss the large-scale geometry implied by the reddening signatures of dust in our near infrared images.Comment: 5 pages, 4 figures, accepted for publication in A&A Letters. A version with high resolution images can be downloaded from http://www.helsinki.fi/~jtkainul/CenALette

Mass reservoirs surrounding massive infrared dark clouds: A view by near-infrared dust extinction

Context: Infrared Dark Clouds (IRDCs) harbor progenitors of high-mass stars. Little is known of the parental molecular clouds of the IRDCs. Aims: We demonstrate the feasibility of the near-infrared (NIR) dust extinction mapping in tracing the parental molecular clouds of IRDCs at the distances of D = 2.5 - 8 kpc. Methods: We derive NIR extinction maps for 10 prominent IRDC complexes using a color-excess mapping technique and NIR data from the UKIDSS/Galactic Plane Survey. We compare the resulting maps to the 13CO emission line data, to the 8 \mu m dust opacity data, and to the millimeter dust emission data. We derive distances for the clouds by comparing the observed NIR source densities to the Besancon stellar distribution model and compare them to the kinematic distance estimates. Results: The NIR extinction maps provide a view to the IRDC complexes over the dynamical range of Av = 2 - 40 mag, in spatial resolution of 30". The NIR extinction data correlate well with the 13CO data and probe a similar gas component, but also extend to higher column densities. The NIR data reveal a wealth of extended structures surrounding the dense gas traced by the 8 \mu m shadowing features and sub-mm dust emission, showing that the clouds contain typically > 10 times more mass than traced by those tracers. The IRDC complexes of our sample contain relatively high amount of high-column density material, and their cumulative column density distributions resemble active nearby star-forming clouds like Orion rather than less active clouds like California. Conclusions: NIR dust extinction data provide a new powerful tool to probe the mass distribution of the parental molecular clouds of IRDCs up to the distances of D = 8 kpc. This encourages for deeper NIR observations of IRDCs, because the sensitivity and resolution of the data can be directly enhanced with dedicated observations.Comment: 22 pages, 24 figures, accepted to A&A. A version with full resolution figures can be downloaded from http://www.mpia-hd.mpg.de/homes/jtkainul/NexusI/NexusI_v1.pd

Can primordial black holes as all dark matter explain fast radio bursts?

Publisher Copyright: © 2021 American Physical Society.Primordial black holes (PBHs) are one of the most interesting nonparticle dark matter (DM) candidates. They may explain all the DM content in the Universe in the mass regime from about 10-14 M to 10-11 M. We study PBHs as the source of fast radio bursts (FRBs) via magnetic reconnection in the event of collisions between them and neutron stars (NSs) in galaxies. We investigate the energy loss of PBHs during PBH-NS encounters to model their capture by NSs. To an order-of-magnitude estimation, we conclude that the parameter space of PBHs being all DM is accidentally consistent with that to produce FRBs with a rate which is the order of the observed FRB rate.Peer reviewe

Probing the evolution of molecular cloud structure II: From chaos to confinement

We present an analysis of the large-scale molecular cloud structure and of the stability of clumpy structures in nearby molecular clouds. In our recent work, we identified a structural transition in molecular clouds by studying the probability distributions of gas column densities in them. In this paper, we further examine the nature of this transition. The transition takes place at the visual extinction of A_V^tail = 2-4 mag, or equivalently, at \Sigma^tail = 40-80 Ms pc^{-2}. The clumps identified above this limit have wide ranges of masses and sizes, but a remarkably constant mean volume density of n = 10^3 cm^{-3}. This is 5-10 times larger than the density of the medium surrounding the clumps. By examining the stability of the clumps, we show that they are gravitationally unbound entities, and that the external pressure from the parental molecular cloud is a significant source of confining pressure for them. Then, the structural transition at A_V^tail may be linked to a transition between this population and the surrounding medium. The star formation rates in the clouds correlate strongly with the total mass in the clumps, i.e, with the mass above A_V^tail, dropping abruptly below that threshold. These results imply that the formation of pressure confined clumps introduces a prerequisite for star formation. Furthermore, they give a physically motivated explanation for the recently reported relation between the star formation rates and the amount of dense material in molecular clouds. Likewise, they give rise to a natural threshold for star formation at A_V^tail.Comment: 11 pages, 12 figures, accepted for publication in Astronomy and Astrophysic