Outskirts of Galaxy Clusters A1139, A1314, A1656, A2040, A 2052, A2107: Star-Formation Rate

We investigate the variation of the fraction of galaxies with suppressed star formation (M_K < ?21 _. ^m 5) and early-type galaxies (frac_E) of the “red sequence” along the projected radius in six galaxy clusters:Coma (A1656), A1139, and A1314 in the Leo supercluster region (z ≈ 0.037) and A2040, A2052, A2107 in the Hercules supercluster region (z ≈ 0.036). According to SDSS (DR10) data, frac_E is the highest in the central regions of galaxy clusters and it is, on the average, equal to 0.62 ± 0.03, whereas in the 2–3R/R_200c interval and beyond the R_sp ≈ 0.95 ± 0.04 R_200m radius that we inferred from the observed profile frac_E is minimal and equal to 0.25 ± 0.02. This value coincides with the estimate frac_E = 0.24 ± 0.01 that we inferred for field galaxies located between the Hercules and Leo superclusters at the same redshifts. We show that the fraction of galaxies with suppressed star formation decreases continuously with cluster radius from 0.87 ± 0.02 in central regions down to 0.43 ± 0.03 in the 2–3 R/R_200c interval and beyond R_sp, but remains, on the average, higher than 26% than the corresponding fraction for field objects. This decrease is especially conspicuous in the galaxy mass interval log M_* [M_⊙] = 9.5–10. We found that galaxies with ongoing star formation have average clustercentric distances 1.5–2.5 R/R_200c and that their radial-velocity dispersions are higher than those of galaxies with suppressed star formation.     

Eruptive Instability of the Magnetic-Flux Rope: Gravitational Force and Mass-Unloading

We investigate the coronal imaging capabilities of the Solar UltraViolet Imager (SUVI) on board the Geostationary Operational Environmental Satellite-R series spacecraft. Nominally Sun-pointed, SUVI provides solar images in six extreme ultraviolet (EUV) wavelengths. On-orbit data indicated that SUVI had sufficient dynamic range and sensitivity to image the corona to the largest heights above the Sun to date while simultaneously imaging the Sun. We undertook a campaign to investigate the existence of the EUV signal well beyond the nominal Sun-centered imaging area of the solar EUV imagers. We off-pointed the SUVI line of sight by almost one imaging area around the Sun. We present the details of the campaign we conducted when the solar cycle was at near the minimum and some results that confirm that EUV emission is present to beyond three solar radii.

     

The Relationship between Multifractal and Entropy Properties of Seismic Noise in Kamchatka and Irregularity of the Earth’s Rotation

Izvestiya, Physics of the Solid Earth - Abstract—The connection between the properties of seismic noise continuously recorded by the network of 21&nbsp;broadband seismic stations in...     

Reply to the Comment by V.A. Saltykov on the Paper “The Relationship between Multifractal and Entropy Properties of Seismic Noise in Kamchatka and Irregularity of the Earth’s Rotation” by A.A. Lyubushin,G.N. Kopylova,and Yu.K. Serafimova

Izvestiya, Physics of the Solid Earth -     

Peculiar motions in the region of the Ursa Major supercluster of galaxies

We have investigated the peculiar motions of clusters of galaxies in the Ursa Major (UMa) supercluster and its neighborhood. Based on SDSS (Sloan Digital Sky Survey) data, we have compiled a sample of early-type galaxies and used their fundamental plane to determine the cluster distances and peculiar velocities. The samples of early-type galaxies in the central regions (within R ₂₀₀) of 12 UMa clusters of galaxies, in three main subsystems of the supercluster—the filamentary structures connecting the clusters, and in nine clusters from the nearest UMa neighborhood have similar parameters. The fairly high overdensity (3 by the galaxy number and 15 by the cluster number) suggests that the supercluster as a whole is gravitationally bound, while no significant peculiar motions have been found: the peculiar velocities do not exceed the measurement errors by more than a factor of 1.5–2. The mean random peculiar velocities of clusters and the systematic deviations from the overall Hubble expansion in the supercluster are consistent with theoretical estimates. For the possible approach of the three UMa subsystems to be confirmed, the measurement accuracy must be increased by a factor of 2–3.     

Diagnostics of a flare on EQ Peg B from optical pulsations

Based on the methods of coronal seismology, we have investigated the ten-second quasi-periodic pulsations of the optical flare emission from the active red dwarf EQ Peg B detected with the William Herschel Telescope on La Palma. We propose and analyze a model in which they could be produced by sausage oscillations of a coronal flare loop. The amplitude and phase relations between the displacement components of the radial oscillations and the conditions for their excitation in loops with footpoints frozen into the photosphere are considered. The temperature (≈6 × 10⁷ K), plasma density (≈2.7 × 10¹¹ cm⁻³), and magnetic field strength (≈540 G) in the region of energy release have been determined. Our estimate of the flare loop length (≈0.4R _⋆) provides evidence for the existence of extended coronae on red dwarf stars.     

Radial oscillations of coronal loops and microwave radiation from solar flares

We consider the damping mechanisms for the radial oscillations of solar coronal loops in the approximation of a thin magnetic flux tube. We show that the free tube oscillations can have a high Q if the plasma density inside the magnetic flux tube is much higher than the density outside. We analyze the effect of radial coronal-loop magnetic-field oscillations on the modulation of the microwave radiation from solar flares. In the case of a nonthermal gyrosynchrotron mechanism, the fluxes from optically thin and optically thick sources are modulated in antiphase. Based on our model, we diagnose the flare plasma. For the event of May 23, 1990, we estimate the spectral index for accelerated electrons, α≈4.4, and the magnetic-field strength in the region of energy release, B≈190 G.     

Mineral inclusions in diamonds from the River Ranch kimberlite, Zimbabwe

More than 99% of mineral inclusions in diamonds from the River Ranch pipe in the Late Archean Limpopo Mobile Belt (Zimbabwe), are phases of harzburgitic paragenesis, namely olivine (Fo_92–93), orthopyroxene (Mg# = 93), G10 garnets and chromites. The diamond inclusion (DI) chemistry demonstrates a limited overlap with River Ranch kimberlite macrocrysts: the DI garnets are more Ca-undersaturated, and DI spinel and garnet are more Mg-rich. Most River Ranch diamond inclusions were equilibrated at T = 1080–1320 °C, P = 47–61 kbar, and f _O2 between IW and WM buffers. The P/T profile beneath the Limpopo Mobile Belt (LMB) is consistent with a paleo-heat flow of 41–42 mW/m², similar to calculations for Roberts Victor, but hotter than for the Finsch, Kimberley, Koffiefontein and Premier Mines. This is ascribed to the younger tectonothermal age of the LMB and its proximity to Late Archean oceans. Like diamond inclusions from all other kimberlites studied, the River Ranch DI have a lithospheric affinity and therefore indicate that an ancient, chemically depleted, thick (at least 200 km) mantle root existed beneath the Limpopo Mobile Belt 530–540 Ma ago. The mantle root might have developed beneath the continental Central Zone of the LMB as early as the Archean, and could be alien to the overthrust allochthonous sheet of the Limpopo Belt. Oxygen fugacity estimates for diamond inclusions at River Ranch are similar to other diamondiferous harzburgites beneath the Kaapvaal craton, indicating that the Kaapvaal mantle as a whole was well buffered and homogeneous with respect to f _O2 at the time of peridotitic diamond crystallization. Received: 11 January 1995 / Accepted: 10 June 1997