We present the radio luminosity function (LF) of flat-spectrum radio quasars (FSRQ), using the the largest and most complete sample to date. Cross-matching between the FIRST 20 cm and GB6 6 cm radio ...surveys, we find 638 flat-spectrum radio sources above 220 mJy at 1.4 GHz; of these, 327 are are classified and verified using optical spectroscopy data, mainly from Sloan Digital Sky Survey Data Release 12. We also considered flat-spectrum radio sources that lack both literature references and optical spectroscopy, and we identified 12 out of the 43 such sources to potentially be FSRQs, using their WISE colors. From the fully identified sample of 242 FSRQs, we derived the radio LF and cosmic evolution of blazars at 1.4 GHz, finding good agreement with previous work at 5 GHz. The number density of FSRQs increases dramatically to a redshift of z ∼ 2 and then declines for higher redshifts. Furthermore, the redshift at which the quasar density peaks is clearly dependent on luminosity, with more luminous sources peaking at higher redshifts. The approximate best-fit LF for a luminosity-dependent evolutionary model is a broken power-law with slopes ∼0.7 and ∼1.7 below and above the break luminosity, erg s−1, respectively.
This paper deals with several properties of calcite crystals. First, the solvated surface energies at 0 K of the {101̅4}, {101̅0}, {112̅0}, {011̅8}, {011̅2}, {0001}, and {213̅4} forms were determined ...by means of the COSMIC method. We find that the presence of water reduces by ∼7–14% the dry surface energy at 0 K, in a homogeneous way. The solvated and dry equilibrium shapes at 0 K result to be nearly homothetic: in both cases the {101̅4}, {101̅0}, {011̅2}, and {0001} forms are present. In a second part of the paper, the free energy at 300 K of the most widely studied {101̅4}/water interface has been determined (γ(101̅4)/w 300 K = 0.412 ± 0.020 J/m2) by combining simple thermodynamic relations and contact angle measurements. Some considerations on the free energy of other interfaces:{101̅0}, {112̅0}, {011̅8}, {011̅2}, {0001}, and {213̅4} are also proposed. We show that our results are consistent with thermodynamic constraints and fit quite well the known dependence of the solubility of calcite on grain size experimentally determined. Furthermore, as a side result and for the first time, on the basis of our estimate of γ(101̅4)/w 300 K and calculated (101̅4) solvated surface energy, the latter affected by the limits of the COSMIC method, a rough estimate of the vibrational energy and entropy (γ(101̅4)/w 300 K,vib) and configurational entropy (γ(101̅4)/w 300 K,config) of the (101̅4)/water interface is obtained: (γ(101̅4)/w 300 K,vib + γ(101̅4)/w 300 K,config) = −0.066 ± 0.038 J/m2. Finally, by applying the classical nucleation theory and our estimate of γ(101̅4)/w 300 K we calculated the activation energy for homogeneous and heterogeneous nucleation at room temperature. We found extremely high values for such thermodynamical quantity, suggesting that the direct formation of calcite should be prevented. This strongly supports the view that calcite formation should proceed throughout the early formation of an amorphous calcium carbonate phase (ACC).
We present a 66 ks Chandra X-ray observation of the galaxy cluster RXJ0334.2−0111. This deep observation revealed a unique bow shock system associated with a wide angle tail (WAT) radio galaxy and ...several intriguing substructures. The temperature across the bow shock jumps by a factor of ∼1.5 (from 4.1 to 6.2 keV), and is consistent with the Mach number M = 1.6
$_{-0.3}^{+0.5}$
. A second inner surface brightness edge is a cold front that marks the border between infalling subcluster cool core and the intracluster medium of the main cluster. The temperature across the cold front increases from 1.3
$_{-0.8}^{+0.3}$
to 6.2
$_{-0.6}^{+0.6}$
keV. We find an overpressurized region ∼250 kpc east of the cold front that is named ‘the eastern extension (EE)’. The EE may be a part of the third subcluster in the ongoing merger. We also find a tail shaped feature that originates near the bow shock and may extend up to a distance of ∼1 Mpc. This feature is also likely overpressurized. The luminous FR-I radio galaxy, 3C89, appears to be the cD galaxy of the infalling subcluster. We estimated 3C89's jet power from jet bending and the possible interaction between the X-ray gas and the radio lobes. A comparison between the shock stand-off distance and the Mach number for all known shock front/cold front combinations suggests that the core is continuously shrinking in size by stripping.
Abstract
Spatially resolved observations of active galactic nuclei (AGN) host galaxies undergoing feedback processes are one of the most relevant avenues through which galactic evolution can be ...studied, given the long-lasting effects AGN feedback has on gas reservoirs, star formation, and AGN environments at all scales. Within this context, we report results from Very Large Telescope/MUSE integral field optical spectroscopy of TN J1049-1258, one of the most powerful radio sources known, at a redshift of 3.7. We detected extended (∼18 kpc) Ly
α
emission, spatially aligned with the radio axis, redshifted by 2250 ± 60 km s
−1
with respect to the host galaxy systemic velocity, and cospatial with UV continuum emission. This Ly
α
emission could arise from a companion galaxy, although there are arguments against this interpretation. Alternatively, it might correspond to an outflow of ionized gas stemming from the radio galaxy. The outflow would be the highest redshift spatially resolved ionized outflow to date. The enormous amount of energy injected, however, appears to be unable to quench the host galaxy’s prodigious star formation, occurring at a rate of ∼4500
M
⊙
yr
−1
, estimated using its far-infrared luminosity. Within the field, we also found two companion galaxies at projected distances of ∼25 and ∼60 kpc from the host, which suggests the host galaxy is harbored within a protocluster.
Abstract
The environment of the high-redshift (
z
= 1.408), powerful radio-loud galaxy 3C 297 has several distinctive features of a galaxy cluster. Among them, a characteristic halo of hot gas ...revealed by Chandra X-ray observations. In addition, a radio map obtained with the Very Large Array shows a bright hotspot in the northwestern direction, created by the interaction of the active galactic nucleus (AGN) jet arising from 3C 297 with its environment. In the X-ray images, emission cospatial with the northwestern radio lobe is detected, and peaks at the position of the radio hotspot. The extended, complex X-ray emission observed with our new Chandra data is largely unrelated to its radio structure. Despite having attributes of a galaxy cluster, no companion galaxies have been identified from 39 new spectra of neighboring targets of 3C 297 obtained with the Gemini Multi-Object Spectrograph. None of the 19 galaxies for which a redshift was determined lies at the same distance as 3C 297. The optical spectral analysis of the new Gemini spectrum of 3C 297 reveals an isolated Type II radio-loud AGN. We also detected line broadening in O
ii
λ
3728 with a FWHM about 1700 km s
−1
and possible line shifts of up to 500–600 km s
−1
. We postulate that the host galaxy of 3C 297 is a fossil group, in which most of the stellar mass has merged into a single object, leaving behind an X-ray halo.
This paper deals with the influence of silicate species on the morphogenesis of BaCO
3 (witherite), one of the main component of “silica/carbonate biomorphs”. The size of barium carbonate crystals ...decreases progressively and significantly with the increasing amount of Na-metasilicate (Na-MTS) in the crystallization environment. When the Na-MTS amount in the aqueous mother solution is less than 500
ppm, single well-shaped micrometric BaCO
3 crystals are obtained. Higher Na-MTS concentrations (4000–5000
ppm) produce polycrystalline structures built by pseudo-hexagonal nano-rods. X-ray powder diffraction (XRPD) diagrams show the decrease of crystal size with Na-MTS concentration and point out as well that silicate groups can be slightly absorbed into the barium carbonate lattice. The last part of the paper is devoted to the first finding, in laboratory, of aragonite polycrystalline structures belonging to the family of “silica/carbonate biomorphs”.
Abstract
Roughly one third of the sources in the Fermi-LAT catalogs are listed as unidentified/unassociated
γ
-ray sources (UGS), i.e., they lack a low-energy counterpart. In addition, there is a ...growing population of blazars of uncertain type (BCUs). Spectroscopic observations are crucial to confirm the blazar nature of the UGSs candidate counterparts and BCUs. Hence, in 2013 we started an optical spectroscopic campaign to carry out the identifications and classifications. In this paper, as a continuation of the campaign we report the spectra of 39 sources: the sample comprises 37 sources classified as BCUs, one source classified as a BL Lac in the Fourth Source Catalog of the Fermi-LAT (4FGL), and one source classified as UGS. We classify 19 of the sources in the sample as BL Lacs, 13 as blazars with nonnegligible host-galaxy emission, six as Flat Spectrum Radio Quasars, and one as a normal elliptical galaxy. The source listed as BL Lac in the 4FGL seems to be a blazar with nonnegligible host-galaxy emission in our observations, most likely due to an ongoing quiescent state. We classified the UGS source as a BL Lac. Six out of the 39 sources were previously reported in the campaign; in general, both the classifications and redshifts are in agreement, except for one of them with no redshift reported before. Altogether, we provided reliable redshift estimates to 21 out of the 39 sources. Finally, we describe the statistics of the data collected in our campaign so far.
Witherite (BaCO3) crystals have been synthesized by mixing BaCl2·2H2O and NaHCO3 aqueous solutions; their growth morphology is characterized by single and twinned individuals both 001 elongated and ...limited by {110} prism and {hhl} bipyramids. When quartz single crystals are used as substrates, heterogeneous nucleation of witherite occurs onto the {101̅0}, {101̅2}, and {011̅2} forms of quartz and {001} witherite lamellae grow along the 100, 001, and 121̅ directions of quartz. This witherite/quartz three-dimensional epitaxy is the first evidence that two-dimensional epitaxial layers of quartz can form as well on witherite nucleating from aqueous solutions containing Na-metasilicate. As it is known, nano-polycrystalline structures, the “silica biomorphs”, are precipitated from such solutions: this implies a very high nucleation frequency of witherite. We propose that this is caused by the lowering of the specific surface energy of witherite for the two-dimensional localized adsorption of silica chains.
The athermal equilibrium shape (ES) of gypsum crystal is calculated, in a vacuum, in the zone interval of the stepped {1k0} forms (3 ≤ k ≤ 8). The surface profiles are obtained by applying either the ...Hartman−Perdok method of the periodic bond chains (PBC) or the method of systematic cuts (SC) generated under the only conditions of stoichiometry, electroneutrality, and annihilation of the dipole moment perpendicular to each d1k0 slice. The specific surface energy values γ1k0 have been calculated, both for ideal and relaxed surface profiles, using a semiempirical potential function proposed by Adam. From calculations, it follows that the ES in the 001 zone is characterized not only by the well-known {120} and {010} flat forms and by the stepped {100} pinacoid but also by the {140} and {180} stepped forms. Further, following the PBC method, the stepped {130} and {170} forms also should enter the ES. Finally, an unambiguous analogy arises between our results and the systematic presence of the {1k0} faces on the giant crystals found in the Naica mine, whose growth occurs very near the equilibrium.
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