The relationship between the emission of coronal lines (CLs) and nuclear activity in 36 Type 1 and 18 Type 2 active galactic nuclei (AGNs) is analyzed, for the first time, based on near-infrared (0.8-2.4 μm) spectra. The eight CLs studied, of Si, S, Fe, Al, and Ca elements and corresponding to ionization potentials (IPs) in the range 125-450 eV, are detected (3σ ) . We found that the non-detection is largely associated with either loss of spatial resolution or increasing object distance: CLs are essentially nuclear and easily lose contrast in the continuum stellar light for nearby sources or get diluted by the strong AGN continuum as the redshift increases. Yet, there are AGNs where the lack of coronal emission, i.e., lines with IP 100 eV, may be genuine. The absence of these lines reflects a non-standard AGN ionizing continuum, namely, a very hard spectrum lacking photons below a few Kev. The analysis of the line profiles points out a trend of increasing FWHM with increasing IPs up to energies around 300 eV, where a maximum in the FWHM is reached. For higher IP lines, the FWHM remains nearly constant or decreases with increasing IPs. We ascribe this effect to an increasing density environment as we approach the innermost regions of these AGNs, where densities above the critical density of the CLs with IPs larger than 300 eV are reached. This sets a strict range limit for the density in the boundary region between the narrow and the broad region of 10 8 -10 9 cm −3 . A relationship between the luminosity of the CLs and that of the soft and hard X-ray emission and the soft X-ray photon index is observed: the coronal emission becomes stronger with both increasing X-ray emission (soft and hard) and steeper X-ray photon index, i.e., softer X-ray spectra. Thus, photoionization appears as the dominant excitation mechanism. These trends hold when considering Type 1 sources only; they get weaker or vanish when including Type 2 sources, very likely because the X-ray emission measured in the latter is not the intrinsic ionizing continuum.
The BL Lac object 3C 66A is one of the most luminous extragalactic sources at TeV γ-rays (VHE, i.e. E > 100 GeV). Since TeV γ-ray radiation is absorbed by the extragalactic background light (EBL), it is crucial to know the redshift of the source in order to reconstruct its original spectral energy distribution, as well as to constrain EBL models. However, the optical spectrum of this BL Lac is almost featureless, so a direct measurement of z is very difficult; in fact, the published redshift value for this source (z = 0.444) has been strongly questioned. Based on EBL absorption arguments, several constraints to its redshift, in the range 0.096 < z < 0.5, were proposed. Since these AGNs are hosted, typically, in early type galaxies that are members of groups or clusters, we have analysed spectro-photometrically the environment of 3C 66A, with the goal of finding the galaxy group hosting this blazar. This study was made using optical images of a 5.5 × 5.5 arcmin 2 field centred on the blazar, and spectra of 24 sources obtained with Gemini/GMOS-N multi-object spectroscopy. We found spectroscopic evidence of two galaxy groups along the blazar's line of sight: one at z 0.020 and a second one at z 0.340. The first one is consistent with a known foreground structure, while the second group here presented has six spectroscopically confirmed members. Their location along a red sequence in the colour-magnitude diagram allows us to identify 34 additional candidate members of the more distant group. The blazar's spectrum shows broad absorption features that we identify as arising in the intergalactic medium, thus allowing us to tentatively set a redshift lower limit at z 3C66A 0.33. As a consequence, we propose that 3C 66A is hosted in a galaxy that belongs to a cluster at z = 0.340.
La existencia de un manuscrito que versa sobre astronomía y cronología redactado a finales del siglo XVII por Antonio Sánchez de Cozar, un humilde sacerdote de ascendencia indígena, ha pasado desapercibida para los historiadores de la ciencia en el país, aun cuando ya a mediados del siglo XIX había sido dado a conocer como pieza literaria. En este trabajo se presenta una síntesis del contenido de ese manuscrito, así como un análisis de algunos aspectos relevantes que muestran un pensamiento original e independiente del autor, tales como su propuesta dinámica del movimiento de los cielos, la introducción de un cielo entre Mercurio y la Luna y la propuesta de reforma al calendario gregoriano. El manuscrito también contiene las primeras efemérides astronómicas realizadas en territorio neogranadino, consistentes en fases lunares y eclipses cuyos tiempos de ocurrencia están referidos a la hora local de una población del Nuevo Mundo: el municipio de Vélez. ©2019. Acad. Colomb. Cienc. Ex. Fis. Nat.
Las cinco cartas redactadas por un viajero europeo anónimo que habría recorrido el virreinato de la Nueva Granada en los años 1803 y 1804, y que fueron luego publicadas en el Diario Político de Santafé de Bogotá en el curso del segundo semestre de 1810, proporcionan información valiosa sobre diversos aspectos de la vida colonial en Santafé y sus alrededores. Estas cartas permiten poner en evidencia ciertas inconsistencias y anacronismos que revelan la intención fundamental de publicitar una situación favorable para los habitantes de Santafé de Bogotá tras los sucesos que iniciaron el interregno previo a su independencia de la corona española. La identidad del autor de estas cinco cartas se aproxima excesivamente a la Alexander von Humboldt, quien había circulado por los mismos lugares dos años y medio antes, en 1801. En ausencia de un registro histórico que permita sustentar el paso del viajero anónimo identificado solo con las iniciales “L. R.”, se sugiere que este hipotético europeo pudo ser, en realidad, una invención de uno de los editores neogranadinos de este diario, probablemente Francisco José de Caldas.
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