Dust evolution in a supernova interacting with the ISM

Supernovae (SN) explosions are thought to be an important source of dust in galaxies. At the same time strong shocks from SNe are known as an efficient mechanism of dust destruction via thermal and kinetic sputtering. A critically important question of how these two hypotheses of SNe activity control the dust budget in galaxies is still not quite clearly understood. In this paper we address this question within 3D multi-fluid hydrodynamical simulations, treating separately the SNe injected dust and the dust pre-existed in ambient interstellar gas. We focus primarily on how the injected and the pre-existing dust is destroyed by shock waves and hot gas in the SN bubble depending on the density of ambient gas. Within our model we estimate an upper limit of the SN-produced dust mass which can be supplied into interstellar medium. For a SN progenitor mass of 30 $M_\odot$ and the ejected dust mass $M_d=1~M_\odot$ we constrain the dust mass that can be delivered into the ISM as $\geq 0.13~M_\odot$, provided that the SN has injected large dust particles with $a\geq 0.1~\mu$m.Comment: 13 pages, 12 figures, accepted to MNRA

Dust-free starburst galaxies at redshifts z>10z>10

One of the most distant galaxies GN-z11 was formed when the Universe was $\le$ 400 Myr old, and it displays a burst-like star formation rate \sim 25~\msun yr$^{-1}$ with a metallicity $Z\sim 0.2\pm 0.1Z_\odot$. It resembles $z=2-3$ galaxies (at ``cosmic noon") except for the fact that the measured reddening $E(B-V)=0.01\pm 0.01$ indicates the presence of little or no dust. This marked absence of dust hints towards violent dynamical events that destroy or evacuate dust along with gas out of the galaxy on a relatively short time scale and make it transparent. We apply a 3D numerical model to infer possible physical characteristics of these events. We demonstrate that the energetics of the observed star formation rate is sufficient to tear apart the dusty veil on time scales of $20-25$ Myr. This can explain the apparent lack of evolution of UV luminosity function of galaxies between and $z\ge 10$ and $z\sim 7$, by compensating for the lower galaxy masses at higher redshift by the absence of dust. We show, however, that this is a temporary phenomenon and soon after the last of the supernovae explosions have taken place, the expanding shell shrinks and obscures the galaxy on time scales of $\approx 5-8$ Myr.Comment: submitted to MNRAS Letters, 5 pages, 4 figure

Weakly mass-loaded accretion disks

Accretion disks with an additional mass input on the disk surface from environment are considered in the limit of low mass input rate, i.e. when the accretion flow remains keplerian. Due to dissipation of kinetic energy of the infalling gas disk temperature increases, and can deviate significantly from standard temperature of reprocessing accretion disks in their outer regions. This increase in temperature produces an excess of emission in a long-wavelength range of the disk spectrum. An illustrative example of the spectrum of a weakly mass-loaded disk (the surface mass input rate Mdot_{load} ~= 1.5 times 10^{-8} Msun yr^{-1}) reasonably reproducing FIR excess observed in CS Chameleon is given.Comment: 12 pages, 6 figures, Latex, Astron. Astrophys. Transact., accepted, Note in the manuscript adde

Unravelling multi-temperature dust populations in the dwarf galaxy Holmberg II

Holmberg II - a dwarf galaxy in the nearby M81 group - is a very informative source of distribution of gas and dust in the interstellar discs. High-resolution observations in the infrared (IR) allows us to distinguish isolated star-forming regions, photodissociation (PDR) and HII regions, remnants of supernovae (SNe) explosions and, as such, can provide information about more relevant physical processes. In this paper we analyse dust emission in the wavelength range 4.5 to 160 micron using the data from IR space observatories at 27 different locations across the galaxy. We observe that the derived spectra can be represented by multiple dust populations with different temperatures, which are found to be independent of their locations in the galaxy. By comparing the dust temperatures with the far ultraviolet (FUV) intensities observed by the UVIT instrument onboard AstroSat, we find that for locations showing a 100 micron peak, the temperature of cold (20 to 30 K) dust grains show a dependence on the FUV intensities, while such dependence is not observed for the other locations. We believe that the approach described here can be a good tool in revealing different dust populations in other nearby galaxies with available high spatial resolution data.Comment: 7 pages, 4 figures, submitted to Letters to MNRA

Star formation in shells of colliding multi-SNe bubbles

It is believed that when bubbles formed by multiple supernovae explosions interact with one another, they stimulate star formation in overlapping shells. We consider the evolution of a shocked layer formed by the collision of two identical bubbles each of which originated from OB clusters of ∼ 50 members and ∼ 50 pc. The clusters are separated by 200-400 pc.We found that depending on evolutionary status of colliding bubbles the shocked layer can either be destroyed into diffuse lumps, or be fragmented into dense clumps: the former occurs in collisions of young bubbles with continuing supernovae explosions, and the latter occurs in older bubble interactions.We argue that fragmentation efficiency in shells depends on external heating: for a heating rate ∼ 7 × 10−24 erg s−1 prevents fragmentation. The clumps formed in freely expanding parts of bubbles are gradually destroyed and disappear on t <∼ 1 Myr,whereas those formed in the overlapping shells survive much longer. Because of this the number of fragments in an isolated bubble begins to decrease after reaching a maximum, while in collision of two old bubbles it fluctuates around 60-70 until longer than t ∼ 5 Myr