We investigate the characteristics of young (<20 Myr) and bright (L X > 1 × 10 36 erg s −1 ) high-mass X-ray binaries (HMXBs) and find the population to be strongly metallicity dependent. We separate the model populations among two distinct formation pathways: (1) systems undergoing active Roche lobe overflow (RLO) and (2) wind accretion systems with donors in the (super)giant stage, which we find to dominate the HMXB population. We find metallicity to primarily affect the number of systems which move through each formation pathway, rather than the observable parameters of systems which move through each individual pathway. We discuss the most important model parameters affecting the HMXB population at both low and high metallicities. Using these results, we show that (1) the population of ultra-luminous X-ray sources can be consistently described by very bright HMXBs which undergo stable RLO with mild super-Eddington accretion and (2) the HMXB population of the bright starburst galaxy NGC 1569 is likely dominated by one extremely metal-poor starburst cluster.
The giant elliptical galaxy NGC 1275, at the centre of the Perseus cluster, is surrounded by a well-known giant nebulosity of emission-line filaments 1,2 , which are plausibly about >10 8 yr old 3 . The filaments are dragged out from the centre of the galaxy by the radio bubbles rising buoyantly in the hot intracluster gas 4 before later falling back. They act as dramatic markers of the feedback process by which energy is transferred from the central massive black hole to the surrounding gas. The mechanism by which the filaments are stabilized against tidal shear and dissipation into the surrounding 4×10 7 K gas has been unclear. Here we report new observations that resolve thread-like structures in the filaments. Some threads extend over 6 kpc, yet are only 70 pc wide. We conclude that magnetic fields in the threads, in pressure balance with the surrounding gas, stabilize the filaments, so allowing a large mass of cold gas to accumulate and delay star formation.The images presented here (Figs. 1-4) were taken with the Advanced Camera for Surveys (ACS) on the NASA Hubble Space Telescope (HST) using three filters; F625W in the red contains the Hα line, F550M is mostly continuum and F435W in the blue which highlights young stars. In Fig. 2 we show part of the Northern filament ~27 kpc from the nucleus (we adopt H 0 =71 km s -1 Mpc -1 which at a redshift 0.0176 for NGC 1275 gives 352 pc arcsec -1 ). The filaments seen in the WIYN groundbased image (right) are just resolved into narrow threads with the HST ACS (see Supplementary Information). This also occurs in many other filaments including the north-west "horseshoe" filament ( Fig. 3) which lies immediately interior to the outer ghost bubble in X-ray images 5 . A fine thread of emission is seen in the Northern filament system extending about 16 arcsec or 5.8 kpc. Averaged over kpc strips it is about 4 pixels (0.2 arcsec) or about 70 pc wide. (This is an upper limit as the point spread function of the ACS is about one half this value.) The aspect ratio (length / thickness) therefore approaches 100. The top of the horseshoe which is about 6 kpc across is similar, as are many other relatively isolated filaments.In order to estimate the required magnetic field we need to know the properties of a filament and its surroundings. We shall concentrate on a thread of radius 35 pc and length 6 kpc at a distance of 25 kpc from the nucleus of NGC 1275 (Fig. 2) as a basic structural unit typical of what is now resolved in the filaments. To estimate the mass for such a thread we scale from the total gas mass of 10 8 M⊙ inferred from CO emission 6 observed in a 22 arcsec IRAM beam on the same Northern filament complex. Assuming that the mass scales with Hα emission, which is the case for the H 2 emission measured with Spitzer 7 , then our fiducial thread has a mass of about 10 6 M⊙. Its mean density is then ~2 cm -3 and perpendicular column density N ~ 4×10 20 cm -2 or Σ ┴ ~ 7×10 -4 g cm -2 . The lengthwise column density, Σ∥, is l/2r times larger.The variation in projected rad...
We study the effect of environment on the properties of type Ia supernovae by analyzing the integrated spectra of 57 local type Ia supernova host galaxies. We deduce from the spectra the metallicity, current star formation rate, and star formation history of the host and compare these to the supernova decline rates. Additionally, we compare the host properties to the difference between the derived supernova distance and the distance determined from the best-fit Hubble law. From this we investigate possible uncorrected systematic effects inherent in
SN 2007od exhibits characteristics that have rarely been seen in a Type IIP supernova (SN). Optical V-band photometry reveals a very steep brightness decline between the plateau and nebular phases of ∼4.5 mag, likely due to SN 2007od containing a low mass of 56 Ni. The optical spectra show an evolution from normal Type IIP with broad Hα emission, to a complex, four-component Hα emission profile exhibiting asymmetries caused by dust extinction after day 232. This is similar to the spectral evolution of the Type IIn SN 1998S, although no early-time narrow (∼200 km s −1 ) Hα component was present in SN 2007od. In both SNe, the intermediate-width Hα emission components are thought to arise in the interaction between the ejecta and its circumstellar medium (CSM). SN 2007od also shows a mid-infrared excess due to new dust. The evolution of the Hα profile and the presence of the mid-IR excess provide strong evidence that SN 2007od formed new dust before day 232. Late-time observations reveal a flattening of the visible light curve. This flattening is a strong indication of the presence of a light echo, which likely accounts for much of the broad, underlying Hα component seen at late times. We believe that the multi-peaked Hα emission is consistent with the interaction of the ejecta with a circumstellar ring or torus (for the inner components at ±1500 km s −1 ) and a single blob or cloud of circumstellar material out of the plane of the CSM ring (for the outer component at −5000 km s −1 ). The most probable location for the formation of new dust is in the cool dense shell created by the interaction between the expanding ejecta and its CSM. Monte Carlo radiative transfer modeling of the dust emission from SN 2007od implies that up to ∼4 × 10 −4 M of new dust has formed. This is similar to the amounts of dust formed in other core-collapse supernovae such as SNe 1999em, 2004et, and 2006jc.
Implications of observed upper limits to the neutral hydrogen content of E and SO galaxies from Paper I are discussed. If gas shed by dying stars is completely retained by these galaxies and exists as H I, these upper limits will be exceeded in only lo9 yr for E's and SO'S and in only 2 x lo8 yr for NGC 4472. Evidently, gas either is hidden in some undetectable form or is removed from the interstellar medium completely. Several schemes to conceal the mass are proposed, but all seem improbable on one or more grounds. Hence a removal mechanism of some kind seems likely. The most satisfactory candidates for this mechanism appear to be a hot galactic wind (Mathews and Baker 1971) or star formation. Several reasons for favoring the wind hypothesis are presented. The paper concludes with a more speculative discussion of the possible role of hot winds in spiral galaxies. Because of similarities in stellar population and velocity dispersion between ellipticals and the bulges of spirals, hot winds may operate in spiral bulges as well. Several properties of galaxies along the Hubble sequence might be partially explained on this basis. In the course of the discussion we summarize several observations which appear to follow logically from the existence of galactic winds: (1) lack of interstellar matter in most early-type galaxies, (2) the existence of young stars and dust in luminous dwarf ellipticals like NGC 205, (3) the fact that radio activity is associated preferentially with massive elliptical galaxies, (4) X-ray sources in clusters of galaxies, and (5) the observed dependence of elliptical metallicity on galaxy mass (Larson 19743). Subject headings: galaxies: generalinterstellar: matterradio sources: 21 cm radiationstars: mass loss
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.