The source of energetic photons that heated and reionized the early Universe remains uncertain. Early galaxies had low metallicity and recent population synthesis calculations suggest that the number ...and luminosity of high-mass X-ray binaries are enhanced in star-forming galaxies with low metallicity, offering a potentially important and previously overlooked source of heating and reionization. Lyman break analogue (LBA) galaxies are local galaxies that strongly resemble the high-redshift, star-forming Lyman break galaxies and have been suggested as local analogues to these metal-deficient galaxies found in the early Universe. We studied a sample of 10 LBAs in order to measure the relation between star formation rate and X-ray luminosity. We found that for LBAs with metallicities in the range 12 + log sub( 10)(O/H) = 8.15-8.80, the L sub( x) -SFR relation was log10(L sub( X)/SFRerg s super( -1) M... yr)=39.85( plus or minus 0.10) in the 0.5-8 keV band with a dispersion of ... = 0.25 dex. This is an enhancement of nearly a factor of 2 in the L sub( 0.5-8...keV)-SFR relation relative to results for nearby, near-solar metallicity galaxies. The enhancement is significant at the 98.2 per cent level (2.4...). Our enhanced L sub( X)/SFR relation is consistent with the metallicity-dependent predicted value from population synthesis models. We discuss the possibility of an L sub( X)-SFR-metallicity plane for star-forming galaxies. These results are important to our understanding of reionization and the formation of early galaxies. (ProQuest: ... denotes formulae/symbols omitted.)
Context. High-mass X-ray binaries (HMXBs) might have contributed a non-negligible fraction of the energy feedback to the interstellar and intergalactic media at high redshift, becoming important ...sources for the heating and ionization history of the Universe. However, the importance of this contribution depends on the hypothesized increase in the number of HMXBs formed in low-metallicity galaxies and in their luminosities. Aims. In this work we test the aforementioned hypothesis, and quantify the metallicity dependence of HMXB population properties. Methods. We compile from the literature a large set of data on the sizes and X-ray luminosities of HMXB populations in nearby galaxies with known metallicities and star formation rates. We use Bayesian inference to fit simple Monte Carlo models that describe the metallicity dependence of the size and luminosity of the HMXB populations. Results. We find that HMXBs are typically ten times more numerous per unit star formation rate in low-metallicity galaxies (12 + log (O / H) < 8, namely <20% solar) than in solar-metallicity galaxies. The metallicity dependence of the luminosity of HMXBs is small compared to that of the population size. Conclusions. Our results support the hypothesis that HMXBs are more numerous in low-metallicity galaxies, implying the need to investigate the feedback in the form of X-rays and energetic mass outflows of these high-energy sources during cosmic dawn.
Formation of a Black Hole in the Dark Mirabel, I. Félix; Rodrigues, Irapuan
Science (American Association for the Advancement of Science),
05/2003, Letnik:
300, Številka:
5622
Journal Article
Recenzirano
We show that the black hole in the x-ray binary Cygnus X-1 was formed in situ and did not receive an energetic trigger from a nearby supernova. The progenitor of the black hole had an initial mass ...greater than 40 solar masses, and during the collapse to form the ~10-solar mass black hole of Cygnus X-1, the upper limit for the mass that could have been suddenly ejected is ~1 solar mass, much less than the mass ejected in a supernova. The observations suggest that high-mass stellar black holes may form promptly, when massive stars disappear silently.
Black holes of stellar mass and neutron stars in binary systems are first
detected as hard X-ray sources using high-energy space telescopes. Relativistic
jets in some of these compact sources are ...found by means of multiwavelength
observations with ground-based telescopes. The X-ray emission probes the inner
accretion disk and immediate surroundings of the compact object, whereas the
synchrotron emission from the jets is observed in the radio and infrared bands,
and in the future could be detected at even shorter wavelengths. Black-hole
X-ray binaries with relativistic jets mimic, on a much smaller scale, many of
the phenomena seen in quasars and are thus called microquasars. Because of
their proximity, their study opens the way for a better understanding of the
relativistic jets seen elsewhere in the Universe. From the observation of
two-sided moving jets it is inferred that the ejecta in microquasars move with
relativistic speeds similar to those believed to be present in quasars. The
simultaneous multiwavelength approach to microquasars reveals in short
timescales the close connection between instabilities in the accretion disk
seen in the X-rays, and the ejection of relativistic clouds of plasma observed
as synchrotron emission at longer wavelengths. Besides contributing to a deeper
understanding of accretion disks and jets, microquasars may serve in the future
to determine the distances of jet sources using constraints from special
relativity, and the spin of black holes using general relativity.
Context. It is well established that between 380 000 and 1 billion years after the Big Bang the Inter Galactic Medium (IGM) underwent a “phase transformation” from cold and fully neutral to warm ...(≈ 104 K) and ionized. Whether this phase transformation was fully driven and completed by photoionization by young hot stars is a question of topical interest in cosmology. Aims. We propose here that besides the ultraviolet radiation from massive stars, feedback from accreting black holes in high-mass X-ray binaries (BH-HMXBs) was an additional, important source of heating and reionization of the IGM in regions of low gas density at large distances from star-forming galaxies. Methods. We use current theoretical models on the formation and evolution of primitive massive stars of low metallicity, and the observations of compact stellar remnants in the near and distant universe, to infer that a significant fraction of the first generations of massive stars end up as BH-HMXBs. Results. The total number of energetic ionizing photons from an accreting stellar black hole in an HMXB is comparable to the total number of ionizing photons of its progenitor star. However, the X-ray photons emitted by the accreting black hole are capable of producing several secondary ionizations and the ionizing power of the resulting black hole could be greater than that of its progenitor. Feedback by the large populations of BH-HMXBs heats the IGM to temperatures of ≈ 104 K and maintains it ionized on large distance scales. Conclusions. BH-HMXBs determine the early thermal history of the universe and maintain it as ionized over large volumes of space in regions of low density. This has a direct impact on the properties of the faintest galaxies at high redshifts, the smallest dwarf galaxies in the local universe, and on the existing and future surveys at radio wavelengths of atomic hydrogen in the early universe.
The Fermi Large Area Telescope is unveiling a large population of otherwise hidden sources of gamma rays.
Recent ground- and space-based telescopes that detect high-energy photons from a few up to ...hundreds of gigaelectron volts (GeV) have opened a new window on the universe. However, because of the relatively poor angular resolution of these telescopes, a large fraction of the thousands of sources of gamma rays observed remains unknown. Compact astrophysical objects are among those high-energy sources, and in the Milky Way there is a particular class called gamma-ray binaries. These are neutron stars or black holes orbiting around massive stars (
1
). On page 189 of this issue, the Fermi Large Area Telescope Collaboration (
2
) use the correlated orbital modulation at gamma-ray, x-ray, and radiowave wavelengths to show that the source 1FGL J1018.6-5856 is a new gamma-ray binary, demonstrating the potential of searches for periodic modulation at gamma rays and other wavelengths to unveil new populations of gamma-ray binaries.
LUMINOUS INFRARED GALAXIES Sanders, D. B; Mirabel, I. F
Annual review of astronomy and astrophysics,
09/1996, Letnik:
34, Številka:
1
Journal Article
Recenzirano
At luminosities above 10
11
,
infrared galaxies become the dominant population of extragalactic objects in
the local Universe (
z
0.3), being more numerous than optically
selected starburst and ...Seyfert galaxies and quasi-stellar objects at comparable
bolometric luminosity. The trigger for the intense infrared emission appears to
be the strong interaction/merger of molecular gas-rich spirals, and the bulk of
the infrared luminosity for all but the most luminous objects is due to dust
heating from an intense starburst within giant molecular clouds. At the highest
luminosities (
L
ir
> 10
12
),
nearly all objects appear to be advanced mergers powered by a mixture of
circumnuclear starburst and active galactic nucleus energy sources, both of
which are fueled by an enormous concentration of molecular gas that has been
funneled into the merger nucleus. These ultraluminous infrared galaxies may
represent an important stage in the formation of quasi-stellar objects and
powerful radio galaxies. They may also represent a primary stage in the
formation of elliptical galaxy cores, the formation of globular clusters, and
the metal enrichment of the intergalactic medium.
Gamma-ray bursts (GRBs) are short, intense flashes of soft gamma-rays coming from the distant Universe. Long-duration GRBs (those lasting more than approximately 2 s) are believed to originate from ...the deaths of massive stars, mainly on the basis of a handful of solid associations between GRBs and supernovae. GRB 060614, one of the closest GRBs discovered, consisted of a 5-s hard spike followed by softer, brighter emission that lasted for approximately 100 s (refs 8, 9). Here we report deep optical observations of GRB 060614 showing no emerging supernova with absolute visual magnitude brighter than M(V) = -13.7. Any supernova associated with GRB 060614 was therefore at least 100 times fainter, at optical wavelengths, than the other supernovae associated with GRBs. This demonstrates that some long-lasting GRBs can either be associated with a very faint supernova or produced by different phenomena.
We report the results of simultaneous multiwavelength observations of the X-ray transient source SWIFT J1753.5-0127 performed with INTEGRAL, RXTE, NTT, REM, and VLA on 2005 August 10-12. The source, ...which underwent an X-ray outburst since 2005 May 30, was observed during the INTEGRAL Target of Opportunity program dedicated to new X-ray novae located in the Galactic halo. Broadband spectra and fast timing variability properties of SWIFT J1753.5-0127 are analyzed together with the optical, near-infrared, and radio data. We show that the source was significantly detected up to 600 keV with Comptonization parameters and timing properties typical of the so-called low/hard state of black hole candidates. We build a spectral energy distribution and show that SWIFT J1753.5-0127 does not follow the usual radio/X-ray correlation of X-ray binaries in the low/hard state. We give estimates of distance and mass. We conclude that SWIFT J1753.5-0127 belongs to the X-ray nova class and that it is likely a black hole candidate transient source of the Galactic halo that remained in the low/hard state during its main outburst. We discuss our results in the context of Comptonization and jet models.
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