Abstract Luminous, compact emission-line galaxies (LCGs) are the most abundant class of confirmed Lyman continuum (LyC) emitters. An optical integral field study of the nearby LCG NGC 2366 reveals an ...outflow originating at the star cluster “knot B” thought to clear a channel via mechanical feedback that enables LyC escape. We observed NGC 2366 with the Chandra X-ray Observatory and detected X-ray emission from a point source coincident with the apex of the outflow at knot B. The pointlike nature and variability of the X-ray emission suggests accretion onto a compact object. The accretion could produce sufficient kinetic energy to power the outflow.
Abstract
We characterize the optical counterparts to the compact X-ray source population within the nearby spiral galaxy M81 using multiband Hubble Space Telescope (HST) imaging data. By comparing ...the optical luminosities and colors measured for candidate donor stars and host clusters to stellar and cluster evolutionary models, respectively, we estimate the likely masses and upper age limits of the field and cluster X-ray binaries. We identify 15 low-mass X-ray binaries (i.e., donor star mass ≲ 3
M
⊙
) within ancient globular clusters, as well as 42 candidate high-mass X-ray binaries (i.e., donor star mass ≳ 8
M
⊙
). To estimate the likelihood of misclassifications, we inject 4000 artificial sources into the HST mosaic image and conclude that our classifications of globular clusters and high-mass X-ray binaries are reliable at the >90% level. We find that globular clusters that host X-ray binaries are on average more massive and more compact than globular clusters that do not. However, there is no apparent correlation between the X-ray brightness of the clusters and their masses or densities, nor are X-ray binary hosts more X-ray luminous than the general field population of low-mass X-ray binaries. This work represents one of the first in-depth analyses of the population of X-ray binaries within globular clusters in a spiral galaxy.
We present new Chandra constraints on the X-ray luminosity functions (XLFs) of X-ray binary (XRB) populations, as well as their scaling relations, for a sample of 38 nearby galaxies (D = 3.4-29 Mpc). ...Our galaxy sample is drawn primarily from the Spitzer Infrared Nearby Galaxies Survey (SINGS) and contains a wealth of Chandra (5.8 Ms total) and multiwavelength data, allowing for star formation rates (SFRs) and stellar masses (M ) to be measured on subgalactic scales. We divided the 2478 X-ray-detected sources into 21 subsamples in bins of specific SFR (sSFR SFR/M ) and constructed XLFs. To model the XLF dependence on sSFR, we fit a global XLF model, containing contributions from high-mass XRBs (HMXBs), low-mass XRBs (LMXBs), and background sources from the cosmic X-ray background that respectively scale with SFR, M , and sky area. We find an HMXB XLF that is more complex in shape than previously reported and an LMXB XLF that likely varies with sSFR, potentially due to an age dependence. When applying our global model to XLF data for each individual galaxy, we discover a few galaxy XLFs that significantly deviate from our model beyond statistical scatter. Most notably, relatively low-metallicity galaxies have an excess of HMXBs above 1038 erg s−1, and elliptical galaxies that have relatively rich populations of globular clusters (GCs) show excesses of LMXBs compared to the global model. Additional modeling of how the XRB XLF depends on stellar age, metallicity, and GC specific frequency is required to sufficiently characterize the XLFs of galaxies.
Abstract
Luminous infrared galaxies (LIRGs), the most extreme star-forming galaxies in the nearby (
D
< 30 Mpc) universe, show a notable X-ray emission deficiency (up to a factor of ∼10) compared ...with predictions from scaling relations of galaxy-wide high-mass X-ray binary (HMXB) luminosity with star formation rate. In the nearby (≈20 Mpc) LIRG NGC 7552, the majority of the IR emission originates in a circumnuclear starburst ring, which has been resolved into several discrete knots of star formation. We present results from recent Chandra observations of NGC 7552, which reveal significant deficits in the 2–7 keV X-ray luminosities from two of the most powerful star-forming knots. We hypothesize that the expected luminous HMXB populations in these knots are either (1) obscured by very large column densities or (2) suppressed due to the knots having relatively high metallicity and/or very young ages (≲5 Myr). We distinguish between these possibilities using data from recent NuSTAR observations, whose sensitivity above 10 keV is capable of uncovering heavily obscured HMXB populations, since emission at these energies is more immune to absorption effects. We find no evidence of a heavily obscured HMXB population in the central region of NGC 7552, suggesting suppressed HMXB formation. We further show that metallicity-dependent scaling relations cannot fully account for the observed deficit from the most powerful star-forming knots or the central region as a whole. Thus, we suggest that recent bursts in local star formation activity likely drive the high
L
IR
within these regions on timescales ≲5 Myr, shorter than the timescale required for the formation of HMXBs.
We present 23 candidate X-ray binaries with luminosities down to 1.8 X 1036 erg s--1, in the nearby starburst galaxy NGC 4449, from observations totaling 105 ks taken with the ACIS-S instrument on ...the Chandra Space Telescope. We determine count rates, luminosities, and colors for each source, and perform spectral fits for sources with sufficient counts. We also compile a new catalog of 129 compact star clusters in NGC 4449 from high-resolution, multi-band optical images taken with the Hubble Space Telescope, doubling the number of clusters known in this galaxy. The UBVI, H Delta *a luminosities of each cluster are compared with predictions from stellar evolution models to estimate their ages and masses. We find strong evidence for a population of very young massive, black hole binaries, which comprise nearly 50% of the detected X-ray binaries in NGC 4449. Approximately a third of these remain within their parent star clusters, which formed Delta *t 6-8 Myr ago, while others have likely been ejected from their parent clusters. We also find evidence for a population of somewhat older X-ray binaries, including both supergiant and Be-binaries, which appear to be associated with somewhat older Delta *t 100-400 Myr star clusters, and one X-ray binary in an ancient ( Delta *t 10 Gyr) globular cluster. Our results suggest that detailed information on star clusters can significantly improve constraints on X-ray binary populations in star-forming galaxies.
Radio Emission from an Ultraluminous X-ray Source Kaaret, Philip; Corbel, Stephane; Prestwich, Andrea H. ...
Science (American Association for the Advancement of Science),
01/2003, Letnik:
299, Številka:
5605
Journal Article
Recenzirano
The physical nature of ultraluminous x-ray sources is uncertain. Stellar-mass black holes with beamed radiation and intermediate black holes with isotropic radiation are two plausible explanations. ...We discovered radio emission from an ultraluminous x-ray source in the dwarf irregular galaxy NGC 5408. The x-ray, radio, and optical fluxes as well as the x-ray spectral shape are consistent with beamed relativistic jet emission from an accreting stellar black hole. If confirmed, this would suggest that the ultraluminous x-ray sources may be stellarmass rather than intermediate-mass black holes. However, interpretation of the source as a jet-producing intermediate-mass black hole cannot be ruled out at this time.
ABSTRACT
Lyman continuum and line emission are thought to be important agents in the reionization of the early Universe. Haro 11 is a rare example of a local galaxy in which Ly α and continuum ...emission have escaped without being absorbed or scattered by ambient gas and dust, potentially as a consequence of feedback from its X-ray sources. We build on our previous Chandra analysis of Haro 11 by analysing three new observations. Our subpixel spatial analysis reveals that the two previously known X-ray sources are each better modelled as ensembles of at least two unresolved point sources. The spatial variability of these components reveals X1 as a dynamical system where one luminous X-ray source (LX ∼ 1041 erg s−1) fades as a secondary source begins to flare. These might be intermediate-mass black holes or low-luminosity active galactic nuclei (AGNs) near the centre of the galaxy in the process of merging. Optical emission line diagnostics drawn from the literature suggest that while the galaxy as a whole is consistent with starburst signatures of ionization, the individual regions wherein the X-ray sources reside are more consistent with AGN/composite classification. The sources in X2 exhibit some degree of flux variability. X2a dominates the flux of this region during most observations (LX ∼ 6 × 1040 erg s−1), and gives the only evidence in the galaxy of a soft ultraluminous X-ray source capable of high-energy winds, which we suggest are responsible for allowing the coincident Ly α emission to escape.
We investigate the future evolution of two extragalactic X-ray binaries: IC10 X-1 and NGC300 X-1. Each consists of a high-mass black hole (BH; ~20-30 M ) accreting from a massive Wolf-Rayet (W-R) ...star companion (20 M ), and both are located in low-metallicity galaxies. We analyze the current state of the systems and demonstrate that both systems will very quickly (0.3 Myr) form close BH-BH binaries with short coalescence time (~3 Gyr) and large chirp mass (~15 M ). The formation of a BH-BH system seems unavoidable, as (1) W-R companions are well within their Roche lobes and do not expand, so no Roche lobe overflow is expected; (2) even intense W-R wind mass loss does not remove sufficient mass to prohibit the formation of the second BH; and (3) even if the BH receives a large natal kick, the systems are very closely bound and are almost impossible to disrupt. As there are two such immediate BH-BH progenitor systems within 2 Mpc, and as the current gravitational-wave instruments LIGO/VIRGO (initial stage) can detect such massive BH-BH mergers out to ~200 Mpc, the empirically estimated detection rate of such inspirals is R = 3.36+8.29 --2.92 at the 99% confidence level. If there is no detection in the current LIGO/VIRGO data (unreleased year of s6 run), the existence of these two massive BH systems poses an interesting challenge. Either the gravitational radiation search is not sensitive to massive inspirals, or there is some fundamental misunderstanding of stellar evolution physics leading directly to the formation of BH-BH binaries.
Abstract
We used archival data from the Chandra X-ray Observatory (Chandra) and the Hubble Space Telescope, to identify 334 candidate X-ray binary systems and their potential optical counterparts in ...the interacting galaxy pair NGC 5194/5195 (M51). We present the catalog and data analysis of X-ray and optical properties for those sources, from the deep 892 ks Chandra observations, along with the magnitudes of candidate optical sources as measured in the 8.16 ks Hubble Space Telescope observations. The X-ray luminosity function of the X-ray sources above a few times 10
36
erg s
−1
follows a power law
N
(
>
L
X
,
b
)
∝
L
X
,
b
1
−
α
with
α
= 1.65 ± 0.03. Approximately 80% of sources are variable over a 30 day window. Nearly half of the X-ray sources (173/334) have an optical counterpart within 0.″5.
The high-energy emission from nearby, star-forming galaxies is dominated by X-ray binaries, where a neutron star or black hole is accreting mass from either a low-mass ( 3 M ) or high-mass ( 8 M ) ...star. Donor stars with intermediate masses 3-7 M are also possible, but rarer in our Galaxy. Since it is not possible to separate low-, intermediate-, and high-mass X-ray binaries (LMXBs, IMXBs, and HMXBs) from their X-ray properties alone, we use optical images of M101 taken with the Hubble Space Telescope to directly constrain the masses of donor stars in X-ray binaries down to 3 M . For X-ray binaries that still live within their parent star cluster, the age of the cluster provides strong constraints on the mass of the donor and hence type of binary. We present the classification, on a source-by-source basis, of 140 X-ray point sources in the nearby spiral galaxy M101 (D = 6.4 0.2 Mpc). We find that, overall, HMXBs appear to follow the spiral arms, while LMXBs dominate the bulge region as expected, but also appear to form an inter-arm disk population. The X-ray luminosity functions for HMXBs and LMXBs are well fit by a power-law distribution, dN/dLX ∝ L , with = −1.71 0.06 (HMXBs) and = −1.96 0.08 (LMXBs), and the brightest sources are consistent with the expectations from sampling statistics without requiring a physical cutoff. Overall, our results for HMXB and LMXB populations agree well with the specific star formation rate map presented for M101 recently by Lehmer and collaborators.
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