The Dynamics of A2125 Miller, Neal A; Owen, Frazer N; Hill, John M ...
Astrophysical journal/The Astrophysical journal,
10/2004, Letnik:
613, Številka:
2
Journal Article
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We present 371 galaxy velocities in the field of the very rich cluster A2125 (z approximately 0.25). These were determined using optical spectroscopy collected over several years from both the WIYN ...3.5 m telescope and NOAO Mayall 4 m telescope. Prior studies at a variety of wavelengths (radio, optical, and X-ray) have indicated that A2125 is a likely cluster-cluster merger, a scenario that we are able to test using our large velocity database. We identified 224 cluster galaxies, which were subjected to a broad range of statistical tests using both positional and velocity information to evaluate the cluster dynamics and substructure. The tests confirmed the presence of substructures within the A2125 system at high significance, demonstrating that A2125 is a complex dynamical system. Comparison of the test results with existing simulations strengthens the merger hypothesis and provides clues about the merger geometry and stage. The merger model for the system can reconcile A2125's low X-ray temperature and luminosity with its apparently high richness and might also explain A2125's high fraction of active galaxies identified in prior radio and optical studies.
To compare procalcitonin (PCT) plasma levels of injured patients with the incidence and severity of systemic inflammatory response syndrome (SIRS), infection, and multiple organ dysfunction syndrome ...(MODS) and to assess the predictive value of PCT for these posttraumatic complications.
Retrospective study comparing patients with mechanical trauma in terms of severity of injury, development of infectious complications, and organ dysfunctions.
Level I trauma center with emergency room, intensive care unit, and research laboratory.
Four hundred five injured patients with an Injury Severity Score of > or =9 points were enrolled in this study from January 1994 to February 1996.
Blood samples were collected on the day of admission and on days 1, 3, 5, 7, 10, 14, and 21 thereafter.
We determined PCT serum levels using a specific immunoluminometric assay. We retrospectively evaluated the occurrence of SIRS, sepsis, and MODS using patients' charts. Mechanical trauma led to increased PCT plasma levels dependent on the severity of injury, with peak values on days 1 and 3 (p < .05) and a continuous decrease within 21 days after trauma. Patients who developed SIRS demonstrated a significant (p < .05) increase of peak PCT plasma levels compared with patients without SIRS. The highest PCT plasma concentrations early after injury were observed in patients with sepsis (6.9+/-2.5 ng/mL; day 1) or severe MODS (5.7+/-2.2 ng/mL; day 1) with a sustained increase (p < .05) for 14 days compared with patients with an uneventful posttraumatic course (1.1+/-0.2 ng/mL). Moreover, these increased PCT plasma levels during the first 3 days after trauma predicted (p < .0001; logistic regression analysis) severe SIRS, sepsis, and MODS.
These data indicate that PCT represents a sensitive and predictive indicator of sepsis and severe MODS in injured patients. Routine analysis of PCT levels seems to aid early recognition of these posttraumatic complications. Thus, PCT may represent a useful marker to monitor the inflammatory status of injured patients at risk.
Results from regular monitoring of relativistic compact binaries like PSR 1913+16 are consistent with the dominant (quadrupole) order emission of gravitational waves (GWs). We show that observations ...associated with the binary black hole (BBH) central engine of blazar OJ 287 demand the inclusion of gravitational radiation reaction effects beyond the quadrupolar order. It turns out that even the effects of certain hereditary contributions to GW emission are required to predict impact flare timings of OJ 287. We develop an approach that incorporates this effect into the BBH model for OJ 287. This allows us to demonstrate an excellent agreement between the observed impact flare timings and those predicted from ten orbital cycles of the BBH central engine model. The deduced rate of orbital period decay is nine orders of magnitude higher than the observed rate in PSR 1913+16, demonstrating again the relativistic nature of OJ 287's central engine. Finally, we argue that precise timing of the predicted 2019 impact flare should allow a test of the celebrated black hole "no-hair theorem" at the 10% level.
New evidence is presented for collimated outflow from a starburst nucleus in the edge-on galaxy NGC 3628. A plume of X-ray emission along the minor axis of this galaxy is suggested by the ...distribution of counts in the softer energy channels of the Einstein Observatory IPC. Plumes of H-alpha emission are visible in a CCD image of the southern minor axis region, at a position angle consistent with that of the X-ray plume, while extended, possibly filamentary, H-alpha emission is visible in the north. Optical spectroscopy along the northern minor axis clearly detects line emission, with line ratios of H-alpha, N II, and S II changing from those characteristic of normal H II regions near the nucleus, to a low-ionization state, consistent with shock heating, farther out. All this evidence, and the IR and radio continuum properties of this galaxy, make NGC 3628 another member of the growing class of galaxies with starburst nuclear activity and outflowing winds, to which NGC 253 and M82 already belong.
We present a set of 180 active galactic nucleus (AGN) candidates based on color selection from the IRAS slow-scan deep observations, with color criteria broadened from the initial Point Source ...Catalog samples so as to include similar objects with redshifts up to z = 1 and allowing for two-band detections. Spectroscopic identifications have been obtained for 80 (44%); some additional identifications are secure based on radio detections or optical morphology, although yet unobserved spectroscopically. These spectroscopic identifications include 13 type 1 Seyfert galaxies, 17 type 2 Seyferts, 29 starburst galaxies, 7 LINER systems, and 13 emission-line galaxies so heavily reddened as to remain of ambiguous classification. The optical magnitudes range from R = 12.0 to 20.5; the counts suggest that incompleteness is important fainter than R = 15.5. Redshifts extend to z = 0.51, with a significant part of the sample at z > 0.2. Even with the relaxed color criteria, this sample includes slightly more AGNs than star-forming systems among those where the spectra contain enough diagnostic feature to make the distinction. The active nuclei include several broad-line objects with strong Fe II emission, and composite objects with the absorption-line signatures of fading starbursts. These AGNs with warm far-IR colors have little overlap with the "red AGNs" identified with 2MASS; only a single Seyfert 1 was detected by 2MASS with J - K > 2. Some reliable IRAS detections have either very faint optical counterparts or only absorption-line galaxies, potentially being deeply obscured AGNs. The IRAS detections include a newly identified symbiotic star, and several possible examples of the "Vega phenomenon," including dwarfs as cool as type K. Appendices detail these candidate stars, and the optical-identification content of a particularly deep set of high-latitude IRAS scans (probing the limits of optical identification from IRAS data alone).
A likely tidal disruption of a star by the intermediate-mass black hole (IMBH) of a dwarf galaxy was recently identified in association with Abell 1795. Without deep spectroscopy for this very faint ...object, however, the possibility of a more massive background galaxy or even a disc-instability flare from a weak active galactic nucleus (AGN) could not be dismissed. We have now obtained 8 h of Gemini spectroscopy which unambiguously demonstrates that the host galaxy is indeed an extremely low mass (M... ~ 3 x 10... M...) galaxy in Abell 1795, comparable to the least massive galaxies determined to host IMBHs via other studies. We find that the spectrum is consistent with the X-ray flare being due to a tidal disruption event rather than an AGN flare. We also set improved limits on the black hole mass (logM./M... ~ 5.3-5.7) and infer a 15 yr X-ray variability of a factor of ...10... The confirmation of this galaxy-black hole system provides a glimpse into a population of galaxies that is otherwise difficult to study, due to the galaxies' low masses and intrinsic faintness, but which may be important contributors to the tidal disruption rate. (ProQuest: ... denotes formulae/symbols omitted.)
A likely tidal disruption of a star by the intermediate-mass black hole (IMBH) of a dwarf galaxy was recently identified in association with Abell 1795. Without deep spectroscopy for this very faint ...object, however, the possibility of a more massive background galaxy or even a disc-instability flare from a weak active galactic nucleus (AGN) could not be dismissed. We have now obtained 8 h of Gemini spectroscopy which unambiguously demonstrates that the host galaxy is indeed an extremely low mass (M... ~ 3 x 10... M...) galaxy in Abell 1795, comparable to the least massive galaxies determined to host IMBHs via other studies. We find that the spectrum is consistent with the X-ray flare being due to a tidal disruption event rather than an AGN flare. We also set improved limits on the black hole mass (logM./M... ~ 5.3-5.7) and infer a 15 yr X-ray variability of a factor of ...10... The confirmation of this galaxy-black hole system provides a glimpse into a population of galaxies that is otherwise difficult to study, due to the galaxies' low masses and intrinsic faintness, but which may be important contributors to the tidal disruption rate. (ProQuest: ... denotes formulae/symbols omitted.)
A likely tidal disruption of a star by the intermediate-mass black hole (IMBH) of a dwarf galaxy was recently identified in association with Abell 1795. Without deep spectroscopy for this very faint ...object, however, the possibility of a more massive background galaxy or even a disc-instability flare from a weak active galactic nucleus (AGN) could not be dismissed. We have now obtained 8 h of Gemini spectroscopy which unambiguously demonstrates that the host galaxy is indeed an extremely low mass (M-star similar to 3 x 10(8) M-circle dot) galaxy in Abell 1795, comparable to the least massive galaxies determined to host IMBHs via other studies. We find that the spectrum is consistent with the X-ray flare being due to a tidal disruption event rather than an AGN flare. We also set improved limits on the black hole mass (logM-lozenge/M-circle dot similar to 5.3-5.7) and infer a 15 yr X-ray variability of a factor of greater than or similar to 10(4). The confirmation of this galaxy-black hole system provides a glimpse into a population of galaxies that is otherwise difficult to study, due to the galaxies' low masses and intrinsic faintness, but which may be important contributors to the tidal disruption rate.
Interstellar dust is still a dominant uncertainty in Astronomy, limiting precision in e.g., cosmological distance estimates and models of how light is re-processed within a galaxy. When a foreground ...galaxy serendipitously overlaps a more distant one, the latter backlights the dusty structures in the nearer foreground galaxy. Such an overlapping or occulting galaxy pair can be used to measure the distribution of dust in the closest galaxy with great accuracy. The STARSMOG program uses Hubble to map the distribution of dust in foreground galaxies in fine (<100 pc) detail. Integral Field Unit (IFU) observations will map the effective extinction curve, disentangling the role of fine-scale geometry and grain composition on the path of light through a galaxy. The overlapping galaxy technique promises to deliver a clear understanding of the dust in galaxies: geometry, a probability function of dimming as a function of galaxy mass and radius, and its dependence on wavelength.
The well-known quasar 3C 48 is the most powerful compact steep-spectrum radio-loud QSO at low redshifts. It also has two unusual optical features within the radius of the radio jet ( similar to 1"): ...(1) an anomalous, high-velocity narrow-line component, and (2) a bright continuum peak (3C 48A) similar to 1" northeast of the quasar. Both of these optical features have been conjectured to be related to the radio jet. We have obtained Gemini North GMOS Integral field unit (IFU) spectroscopy of the central region around 3C 48. We use the unique features of the IFU data to remove unresolved emission at the position of the quasar. The resolved emission at the wavelength of the high-velocity component is peaked unk0.25" north of the quasar, at the same position angle as the base of the radio jet. These observations appear to confirm that this high-velocity gas is connected with the radio jet. However, most of the emission comes from a region where the jet is still well collimated, rather than from the regions where the radio maps indicate strong disruption. We also present the results of HST STIS spectroscopy of 3C 48A. We show that 3C 48A is dominated by stars with a luminosity-weighted age of similar to 1.4 x 10 unk yr, substantially older than any reasonable estimate for the age of the radio source. Thus, 3C 48A almost certainly cannot be attributed to jet-induced star formation. The host galaxy of 3C 48 is clearly the result of a merger, and 3C 48A seems much more likely to be the distorted nucleus of the merging partner in which star formation was induced during the previous close passage.
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