A Simple Measurement of Turbulence in Cores of Galaxy Clusters

Using a simple model, we study the effects of turbulence on the motion of bubbles produced by AGN jet activities in the core of a galaxy cluster. We focus on the turbulence with scales larger then the size of the bubbles. We show that for a bubble pair with an age of ~10^8 yr, the projected angle between the two vectors from the cluster center to the two bubbles should be ~> 90 degree and the ratio of their projected distances from the cluster center should be ~< 2.5, if the velocity and scale of the turbulence are ~250 km s^-1 and ~20 kpc, respectively. The positions of the bubbles observed in the Perseus cluster suggest that the turbulent velocity is ~>100 km s^-1 for the cluster.Comment: Accepted for publication in ApJ

Excess Hard X-ray Emission from the Obscured Low Luminosity AGN In the Nearby Galaxy M 51 (NGC 5194)

We observed the nearby galaxy M~51 (NGC 5194) with BeppoSAX. The X-ray properties of the nucleus below 10 keV are almost the same as the ASCA results regarding the hard component and the neutral Fe K$\alpha$ line, but the intensity is about half of the ASCA 1993 data. Beyond this, in the BeppoSAX PDS data, we detected a bright hard X-ray emission component which dominates above 10 keV. The 10 -- 100 keV flux and luminosity of this component are respectively $2\times10^{-11}$ erg s$^{-1}$ cm$^{-2}$ and $2\times10^{41}$ erg s$^{-1}$. These are about 10 times higher than the extrapolation from the soft X-ray band, and similar to the flux observed with Ginga, which found a bright power law component in 2 -- 20 keV band. Considering other wavelength properties and the X-ray luminosity, together with strong neutral Fe K line, the hard X-ray emission most likely arises from a low luminosity active nucleus, which is obscured with a column density of $\sim10^{24}$cm$^{-2}$. This suggests that hidden low luminosity AGNs may well be present in other nearby galaxies. We interpret the discrepancy between Ginga and other X-ray satellites to be due to a large variability of absorption column density toward the line of sight over several years, suggesting that the Compton thick absorption material may be present on a spatial scale of a parsec. Apart from the nucleus, several ultra-luminous off-nuclear X-ray sources detected in M~51 exhibit long-term time variability, suggesting the state transition similar to that observed in Galactic black hole candidates.Comment: 18 pages, 8 figures, accepted for A&

O cultivo de hortaliças.

Classificação das hortaliças; Clima e cultivares; Modos de plantio; Ferramentas e equipamentos; A escolha do local; preparo do terreno; Adubos e adubação; Adubação em cobertura; Produção e transplantio de mudas; Irrigações ou regas; Capinas; Releação; mDebaste; Desbrota; Estaqueamento; Amostoa; Controle de pragas e doenças; Colheita; rotação de culturas; Produção de hortaliças em recipientes; instruções específicas para o plantio de algumas hortaliças; Abóbora e moranga; Abobrinha; Agrião; Aipo ou salsão; Alcachofra; Alface e chicória; Alho; Alho-porró; Almeirão; Aspargo; Batata; Batata-baroa ou mandioquinha-slasa; Batata-doce; Berinjela e jiló; Beterraba; Cebola; Cebolinha; Cenoura; Chuchu; coentro; Couve, couve-brócolo, couve-flor e repolho; couve-chinesa; Ervilha (grãos e vagens verdes); Evrilha tipo industrial; Espinafre; Feijão-vagem; Maxixe; Melancia; Melão; Milho-doce, milho verde e milho-pipoca; Morango; Nabo ou rábano; Pimenta; Pimentão; Pepino; Quiabo; Rabanete; Rúcula; Salsa; Tomate.bitstream/item/162331/1/O-cultivo-de-hortalicas.pd

Como previnir o tombamento em mudas de hortaliças.

bitstream/item/23626/1/lopes-como.pd

ASCA observations of the nearby galaxies Dwingeloo 1 and Maffei 1

We present ASCA observations of the nearby galaxies Dwingeloo 1 (Dw1) and Maffei 1 (Mf1). X-ray sources are clearly detected within 3 arcminutes of the optical nuclei of both galaxies. Despite the low Galactic latitude of these fields (|b|<1\degmark) we conclude, on probability and spectral grounds, that the detected sources are intrinsic to these galaxies rather than foreground or background interlopers. The Dw1 source, designated Dw1-X1, is interpreted as being either a hyper-luminous X-ray binary (with a 0.5--10\,keV luminosity of more than 10^{39}\ergps) or an X-ray bright supernova. The Mf1 emission is hard and extended, suggesting that it originates from a population of X-ray binaries. Prompted by the Dw1-X1 results, we discuss the nature of hyper-luminous X-ray binary systems. Such sources are commonly seen in nearby galaxies with a frequency of approximately one per galaxy. We present a possible connection between these luminous systems and Galactic superluminal sources.Comment: 9 pages (4 ps figures included). Accepted for publication in MNRAS. Higher quality reproductions of Figure 1 available upon reques

The Declined Activity in the Nucleus of NGC 1316

NGC 1316 (Fornax A) is a radio galaxy with prototypical double lobes, where the magnetic field intensity is accurately measured via the inverse-Compton technique. The radio-emitting electrons in the lobes are inferred to have a synchrotron life time of 0.1 Gyr. Considering the lobe energetics, we estimate the past nuclear X-ray luminosity of NGC 1316 to be at least 4 times 10^{34} W (4 times 10^{41} erg s^{-1}). Thus, the nucleus was rather active at least 0.1 Gyr ago. In contrast, we confirmed with ASCA and ROSAT that the nucleus of NGC 1316 is very faint in X-rays at present, with the 2--10 keV luminosity of any AGN-like hard component being < 2 times 10^{33} W (2 times 10^{40} erg s^{-1}) even assuming a nuclear obscuration up to 10^{28} m^{-2} (10^{24} cm^{-2}). This is at least an order of magnitude lower than the estimated past activity, indicating that the nucleus is presently very inactive. From these two results, we conclude that the nucleus of NGC 1316 has become dormant during the last 0.1 Gyr. This suggests the possible abundance of ``dormant'' quasars in nearby galaxies.Comment: 7 pages, 2 figures, to be published in the Astrophysical Journal Letter

Contaminação com patógenos em sistemas hidropônico: como aparecem e como evitar.

bitstream/CNPH-2009/31446/1/cot_31.pd

High Resolution Infrared Imaging of the Compact Nuclear Source in NGC4258

We present high resolution imaging of the nucleus of NGC4258 from 1 micron to 18 microns. Our observations reveal that the previously discovered compact source of emission is unresolved even at the near-infrared resolution of about 0.2 arcsec FWHM which corresponds to about 7 pc at the distance of the galaxy. This is consistent with the source of emission being the region in the neighborhood of the purported 3.5*10^7 M_sun black hole. After correcting for about 18 mags of visual extinction, the infrared data are consistent with a F_nu \propto nu^(-1.4+/-0.1) spectrum from 1.1 micron to 18 micron, implying a non-thermal origin. Based on this spectrum, the total extinction corrected infrared luminosity (1-20 micron) of the central source is 2*10^8 L_sun. We argue that the infrared spectrum and luminosity of the central source obviates the need for a substantial contribution from a standard, thin accretion disk at these wavelengths and calculate the accretion rate through an advection dominated accretion flow to be Mdot \sim 10^(-3) M_sun/yr. The agreement between these observations and the theoretical spectral energy distribution for advection dominated flows provides evidence for the existence of an advection dominated flow in this low luminosity AGN.Comment: 21 pages, 5 figures, Appearing in Mar 2000 ApJ vol. 53

Cultivo protegido do tomateiro.

bitstream/item/141465/1/digitalizar0057.pd