We use three-dimensional hydrodynamic simulations of vertically stratified patches of galactic discs to study how the spatio-temporal clustering of supernovae (SNe) enhances the power of galactic winds. SNe that are randomly distributed throughout a galactic disc drive inefficient galactic winds because most supernova remnants lose their energy radiatively before breaking out of the disc. Accounting for the fact that most star formation is clustered alleviates this problem. Super-bubbles driven by the combined effects of clustered SNe propagate rapidly enough to break out of galactic discs well before the clusters' SNe stop going off. The radiative losses post-breakout are reduced dramatically and a large fraction ($\gtrsim 0.2$) of the energy released by SNe vents into the halo powering a strong galactic wind. These energetic winds are capable of providing strong preventative feedback and eject substantial mass from the galaxy with outflow rates on the order of the star formation rate. The momentum flux in the wind is only of order that injected by the SNe, because the hot gas vents before doing significant work on the surroundings. We show that our conclusions hold for a range of galaxy properties, both in the local Universe (e.g., M82) and at high redshift (e.g., $z \sim 2$ star forming galaxies). We further show that if the efficiency of forming star clusters increases with increasing gas surface density, as suggested by theoretical arguments, the condition for star cluster-driven super-bubbles to break out of galactic discs corresponds to a threshold star formation rate surface density for the onset of galactic winds $\sim 0.03$ M$_\odot$ yr$^{-1}$ kpc$^{-2}$, of order that observed.
We present an analytic model for clustered supernovae (SNe) feedback in galaxy disks, incorporating the dynamical evolution of superbubbles formed from spatially overlapping SNe remnants. We propose two realistic outcomes for the evolution of superbubbles in galactic disks: (1) the expansion velocity of the shock front falls below the turbulent velocity dispersion of the ISM in the galaxy disk, whereupon the superbubble stalls and fragments, depositing its momentum entirely within the galaxy disk, or (2) the superbubble grows in size to reach the gas scale height, breaking out of the galaxy di…
We compare an analytic model for the evolution of supernova-driven superbubbles with observations of local and high-redshift galaxies, and the properties of intact HI shells in local star-forming galaxies. Our model correctly predicts the presence of superwinds in local star-forming galaxies (e.g., NGC 253) and the ubiquity of outflows near $z \sim 2$. We find that high-redshift galaxies may `capture' 20-50\% of their feedback momentum in the dense ISM (with the remainder escaping into the nearby CGM), whereas local galaxies may contain $\lesssim$10\% of their feedback momentum from the centra…
We study the conditions for disk galaxies to produce superbubbles that can break out of the disk and produce a galactic wind. We argue that the threshold surface density of supernovae rate for seeding a wind depends on the ability of superbubble energetics to compensate for radiative cooling. We first adapt Kompaneets formalism for expanding bubbles in a stratified medium to the case of continuous energy injection and include the effects of radiative cooling in the shell. With the help of hydrodynamic simulations, we then study the evolution of superbubbles evolving in stratified disks with ty…
Young stars typically form in star clusters, so the supernovae (SNe) they produce are clustered in space and time. This clustering of SNe may alter the momentum per SN deposited in the interstellar medium (ISM) by affecting the local ISM density, which in turn affects the cooling rate. We study the effect of multiple SNe using idealized 1D hydrodynamic simulations which explore a large parameter space of the number of SNe, and the background gas density and metallicity. The results are provided as a table and an analytic fitting formula. We find that for clusters with up to ~100 SNe the asympt…
Aims. The aim is to explore the interstellar medium around the dust bubble N131 and search for signatures of star formation. Methods. We perform a multiwavelength study around the N131 with data taken from large-scale surveys of infrared observation with online archive. We present new observations of three CO J = 1 - 0 isotope variants from Purple Mountain Observatory 13.7 m telescope. We analyze the distribution of the molecular gas and dust in the environment of the N131. We use color-color diagrams to search for young stellar objects and identify exciting star candidates. Results. The kinem…
We address a simple model where the Kennicutt-Schmidt (KS) relation between the macroscopic densities of star-formation rate (SFR, $ρ_{\rm sfr}$) and gas ($n$) in galactic discs emerges from self-regulation of the SFR via supernova feedback. It arises from the physics of supernova bubbles, insensitive to the microscopic SFR recipe and not explicitly dependent on gravity. The key is that the filling factor of SFR-suppressed supernova bubbles self-regulates to a constant, $f\sim 0.5$. Expressing the bubble fading radius and time in terms of $n$, the filling factor is $f \propto S\,n^{-s}$ with $…
We study the merging and evolution of isolated supernovae (SNe) remnants in a stellar cluster into a collective superbubble, with the help of 3-D hydrodynamic simulations. We particularly focus on the transition stage when the isolated SNe remnants gradually combine to form a superbubble. We find that when the SN rate is high ($ν_{\rm sn}\sim 10^{-9}$ pc$^{-3}$ yr$^{-1}$), the merging phase lasts for $\sim 10^4$ yr, for $n=1\hbox{--}10$ cm$^{-3}$, and the merging phase lasts for a longer time ($\sim 0.1$ Myr or more) for lower SN rates ($ν_{\rm sn}\le 10^{-10}$ pc$^{-3}$ yr$^{-1}$). During thi…
After discovery of the Fermi bubbles, giant structures observed in radio to X-rays have been discussed as possi- ble evidence of past activities in the Galactic Center (GC). We report here on the analysis of Suzaku data pointing around the Loop I arc. The diffuse X-ray emission was well represented by the three-component model: (1) an unabsorbed thermal plasma with kT ~ 0.1 keV either from the Local Hot Bubble (LHB) and/or solar wind charge exchange (SWCX), (2) an absorbed thermal plasma regarded as a contribution from the Loop I and the Galactic halo (GH), and (3) an absorbed power-law compon…
Dust destruction in bubbles driven by multiple supernovae explosions
Lebedev Physical Institute, Russian Academy of Sciences（列别捷夫物理研究所，俄罗斯科学院）；Department of Physical Sciences, Indian Institute of Science Education and Research (IISER)（印度科学教育与研究学院物理科学系）
We performed a multi-wavelength study toward the filamentary cloud G47.06+0.26 to investigate the gas kinematics and star formation. We present the 12CO (J=1-0), 13CO (J=1-0) and C18O (J=1-0) observations of G47.06+0.26 obtained with the Purple Mountain Observation (PMO) 13.7 m radio telescope to investigate the detailed kinematics of the filament. The 12CO (J=1-0) and 13CO (J=1-0) emission of G47.06+0.26 appear to show a filamentary structure. The filament extends about 45 arcmin (58.1 pc) along the east-west direction. The mean width is about 6.8 pc, as traced by the 13CO (J=1-0) emission. G…
We use magnetohydrodynamical simulations of converging warm neutral medium flows to analyse the formation and global evolution of magnetised and turbulent molecular clouds subject to supernova feedback from massive stars. We show that supernova feedback alone fails to disrupt entire, gravitationally bound, molecular clouds, but is able to disperse small--sized (~10 pc) regions on timescales of less than 1 Myr. Efficient radiative cooling of the supernova remnant as well as strong compression of the surrounding gas result in non-persistent energy and momentum input from the supernovae. However,…
We have investigated 25 H II regions with bubble morphology in 13CO(1-0) and infrared data, to search the quantitative evidence for the triggering star formation by collect and collapse (CC) and radiatively driven implosion (RDI) models. These H II regions display the morphology of the complete or partial bubble at 8 um, which all are associated with the surrounding molecular clouds. We obtained that the electron temperature ranges from 5627 K to 6839 K in these H II regions, and the averaged electron temperature is 6083 K. The age of these H II regions is from 3.0\times10^{5} yr to 1.7\times1…
We performed a multiwavelength study toward infrared dark cloud (IRDC) G34.43+0.24. New maps of 13CO $J$=1-0 and C18}O J=1-0 were obtained from the Purple Mountain Observatory (PMO) 13.7 m radio telescope. At 8 um (Spitzer - IRAC), IRDC G34.43+0.24 appears to be a dark filament extended by 18 arcmin along the north-south direction. Based on the association with the 870 um and C18O J=1-0 emission, we suggest that IRDC G34.43+0.24 should not be 18 arcmin in length, but extend by 34 arcmin. IRDC G34.43+0.24 contains some massive protostars, UC H II regions, and infrared bubbles. The spatial exten…
We use a new contiguous imaging survey conducted using the Dark Energy Camera to investigate the distribution and properties of young stellar populations in the Magellanic inter-Cloud region. These young stars are strongly spatially clustered, forming a narrow chain of low-mass associations that trace the densest HI gas in the Magellanic Bridge and extend, in projection, from the SMC to the outer disk of the LMC. The associations in our survey footprint have ages $\lesssim 30$ Myr, masses in the range $\sim 100-1200\,{\rm M}_\odot$, and very diffuse structures with half-light radii of up to $\…
Most stars are born in rich young stellar clusters (YSCs) embedded in giant molecular clouds. The most massive stars live out their short lives there, profoundly influencing their natal environments by ionizing HII regions, inflating wind-blown bubbles, and soon exploding as supernovae. Thousands of lower-mass pre-main sequence stars accompany the massive stars, and the expanding HII regions paradoxically trigger new star formation as they destroy their natal clouds. While this schematic picture is established, our understanding of the complex astrophysical processes involved in clustered star…
It is well known that most of the stars form in rich clusters. However, recent $Spitzer$ observations have shown that a significant number of stars also form in distributed mode, origin of which is not well understood. In this work, we aim to investigate clustered and distributed mode of star formation in the W4 complex. To do so, we identified and characterized the young stellar population associated with the region using homogeneous infra-red data-sets obtained from 2MASS, GLIMPSE, MIPS and WISE surveys. We make stellar surface density and minimum spanning tree maps to identify young cluster…
IRAS 22134+5834 was observed in the centimeter with (E)VLA, 3~mm with CARMA, 2~mm with PdBI, and 1.3~mm with SMA, to study the continuum emission as well as the molecular lines, that trace different physical conditions of the gas to study the influence of massive YSOs on nearby starless cores, and the possible implications in the clustered star formation process. The multi-wavelength centimeter continuum observations revealed two radio sources within the cluster, VLA1 and VLA2. VLA1 is considered to be an optically thin UCHII region with a size of 0.01~pc and sits at the edge of the near-infra…
