Calcification in Aging Canine Aortic Valve

Aging changes of aortic valves are thought to underlie the mechanism of calcification, which leads to calcific aortic stenosis in humans. The study of calcification in the aging valvular connective tissue has been hindered by the lack of a suitable animal model. In search of the model, canine aortic valves demonstrated age changes including calcification remarkably similar to those in humans. The mechanism of calcification was studied in the aortic valves of aged Beagles by electron microscopy. Fibroblasts in the canine aortic valves showed the most prominent age changes. The cells accumulated numerous residual bodies and appeared to disintegrate. The resultant membranous cellular degradation products which sequestered in the extracellular space were the nidi of calcification. It appeared that the membrane of cell debris played an important role in calcification. Canine aortic valve is an ideal model for the study of calcification in relation to aging of the valvular connective tissue

Linking black-hole growth with host galaxies: The accretion-stellar mass relation and its cosmic evolution

Previous studies suggest that the growth of supermassive black holes (SMBHs) may be fundamentally related to host-galaxy stellar mass ($M_\star$). To investigate this SMBH growth-$M_\star$ relation in detail, we calculate long-term SMBH accretion rate as a function of $M_\star$ and redshift [$\overline{\rm BHAR}(M_\star, z)$] over ranges of $\log(M_\star/M_\odot)=\text{9.5--12}$ and $z=\text{0.4--4}$. Our $\overline{\rm BHAR}(M_\star, z)$ is constrained by high-quality survey data (GOODS-South, GOODS-North, and COSMOS), and by the stellar mass function and the X-ray luminosity function. At a given $M_\star$, $\overline{\rm BHAR}$ is higher at high redshift. This redshift dependence is stronger in more massive systems (for $\log(M_\star/M_\odot)\approx 11.5$, $\overline{\rm BHAR}$ is three decades higher at $z=4$ than at $z=0.5$), possibly due to AGN feedback. Our results indicate that the ratio between $\overline{\rm BHAR}$ and average star formation rate ($\overline{\rm SFR}$) rises toward high $M_\star$ at a given redshift. This $\overline{\rm BHAR}/\overline{\rm SFR}$ dependence on $M_\star$ does not support the scenario that SMBH and galaxy growth are in lockstep. We calculate SMBH mass history [$M_{\rm BH}(z)$] based on our $\overline{\rm BHAR}(M_\star, z)$ and the $M_\star(z)$ from the literature, and find that the $M_{\rm BH}$-$M_\star$ relation has weak redshift evolution since $z\approx 2$. The $M_{\rm BH}/M_\star$ ratio is higher toward massive galaxies: it rises from $\approx 1/5000$ at $\log M_\star\lesssim 10.5$ to $\approx 1/500$ at $\log M_\star \gtrsim 11.2$. Our predicted $M_{\rm BH}/M_\star$ ratio at high $M_\star$ is similar to that observed in local giant ellipticals, suggesting that SMBH growth from mergers is unlikely to dominate over growth from accretion.Comment: 27 pages, 21 figures, 2 tables; MNRAS accepte

Does black-hole growth depend on the cosmic environment?

It is well known that environment affects galaxy evolution, which is broadly related to supermassive black hole (SMBH) growth. We investigate whether SMBH evolution also depends on host-galaxy local (sub-Mpc) and global (≈1–10 Mpc) environment. We construct the surface-density field (local environment) and cosmic web (global environment) in the Cosmic Evolution Survey (COSMOS) field at z = 0.3–3.0. The environments in COSMOS range from the field to clusters (Mhalo ≲ 1014 M⊙), covering the environments where ≈99 per cent of galaxies in the Universe reside. We measure sample-averaged SMBH accretion rate ( BHAR¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ) from X-ray observations, and study its dependence on overdensity and cosmic-web environment at different redshifts while controlling for galaxy stellar mass (M⋆). Our results show that BHAR¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ does not significantly depend on overdensity or cosmic-web environment once M⋆ is controlled, indicating that environment-related physical mechanisms (e.g. tidal interaction and ram-pressure stripping) might not significantly affect SMBH growth. We find that BHAR¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ is strongly related to host-galaxy M⋆, regardless of environment

Peroxisomes in intestinal and gallbladder epithelial cells of the stickleback, Gasterosteus aculeatus L. (Teleostei)

The occurrence of microbodies in the epithelial cells of the intestine and gallbladder of the stickleback, Gasterosteus aculeatus L., is described. In the intestine the organelles are predominantly located in the apical and perinuclear zone of the cells and may contain small crystalline cores. In gallbladder epithelial cells the microbodies are distributed randomly. The latter organdies are characterized by the presence of large crystalloids. Cytochemical and biochemical experiments show that catalase and D-amino acid oxidase are main matrix components of the microbodies in both the intestinal and gallbladder epithelia. These organelles therefore are considered peroxisomes. In addition, in intestinal mucosa but not in gallbladder epithelium a low activity of palmitoyl CoA oxidase was detected biochemically. Urate oxidase and L-α hydroxy acid oxidase activities could not be demonstrated.

Identifying Luminous AGN in Deep Surveys: Revised IRAC Selection Criteria

Spitzer IRAC selection is a powerful tool for identifying luminous AGN. For deep IRAC data, however, the AGN selection wedges currently in use are heavily contaminated by star-forming galaxies, especially at high redshift. Using the large samples of luminous AGN and high-redshift star-forming galaxies in COSMOS, we redefine the AGN selection criteria for use in deep IRAC surveys. The new IRAC criteria are designed to be both highly complete and reliable, and incorporate the best aspects of the current AGN selection wedges and of infrared power-law selection while excluding high redshift star-forming galaxies selected via the BzK, DRG, LBG, and SMG criteria. At QSO-luminosities of log L(2-10 keV) (ergs/s) > 44, the new IRAC criteria recover 75% of the hard X-ray and IRAC-detected XMM-COSMOS sample, yet only 38% of the IRAC AGN candidates have X-ray counterparts, a fraction that rises to 52% in regions with Chandra exposures of 50-160 ks. X-ray stacking of the individually X-ray non-detected AGN candidates leads to a hard X-ray signal indicative of heavily obscured to mildly Compton-thick obscuration (log N_H (cm^-2) = 23.5 +/- 0.4). While IRAC selection recovers a substantial fraction of luminous unobscured and obscured AGN, it is incomplete to low-luminosity and host-dominated AGN.Comment: 22 pages, 15 figures, accepted for publication in ApJ, full resolution version available at http://www.stsci.edu/~donley/iragn_paper

Chandra X-Ray Observations of Two Unusual BAL Quasars

We report sensitive Chandra X-ray non-detections of two unusual, luminous Iron Low-Ionization Broad Absorption Line Quasars (FeLoBALs). The observations do detect a non-BAL, wide-binary companion quasar to one of the FeLoBAL quasars. We combine X-ray-derived column density lower limits (assuming solar metallicity) with column densities measured from ultraviolet spectra and CLOUDY photoionization simulations to explore whether constant density slabs at broad line region densities can match the physical parameters of these two BAL outflows, and find that they cannot. In the "overlapping-trough" object SDSS J0300+0048, we measure the column density of the X-ray absorbing gas to be N_H >= 1.8 x 1024 cm-2. From the presence of Fe II UV78 absorption but lack of Fe II UV195/UV196 absorption, we infer the density in that part of the absorbing region to be n_e ~ 106 cm-3. We do find that a slab of gas at that density might be able to explain this object's absorption. In the Fe III-dominant object SDSS J2215-0045, the X-ray absorbing column density of N_H >= 3.4 x 1024 cm-2 is consistent with the Fe III-derived N_H >= 2 x 1022 cm-2 provided the ionization parameter is log U > 1.0 for both the n_e = 1011 cm-3 and n_e = 1012 cm-3 scenarios considered (such densities are required to produce Fe III absorption without Fe II absorption). However, the velocity width of the absorption rules out its being concentrated in a single slab at these densities. Instead, this object's spectrum can be explained by a low density, high ionization and high temperature disk wind that encounters and ablates higher density, lower ionization Fe III-emitting clumps.Comment: 18 pages, 6 figure