Intermediate-Mass Black Holes in Globular Clusters

There have been reports of possible detections of intermediate-mass black holes (IMBHs) in globular clusters (GCs). Empirically, there exists a tight correlation between the central supermassive black hole (SMBH) mass and the mean velocity dispersion of elliptical galaxies, "pseudobulges" and classical bulges of spiral galaxies. We explore such a possible correlation for IMBHs in spherical GCs. In our model of self-similar general polytropic quasi-static dynamic evolution of GCs, a criterion of forming an IMBH is proposed. The key result is M(BH) = L o^1/(1-n) where M(BH) is the IMBH mass, o is the GC mean stellar velocity, L is a coefficient, and 2/3 < n < 1

Detailed study of B037 based on {\sl HST} images

B037 is of interest because it is both the most luminous and the most highly reddened cluster known in M31. Images of deep observations and of highly spatial resolutions with the Advanced Camera for Surveys on the {\sl HST} firstly show that this cluster is crossed by a dust lane. Photometric data in the F606W and F814W filters obtained in this paper provide that, colors of ($\rm {F606W-F814W}$) in the dust lane are redder $\sim 0.4$ mags than ones in the other regions of B037. The {\sl HST} images show that, this dust lane seems to be contained in B037, not from the M31 disk or the Milky Way. As we know, the formation of dust requires gas with a rather high metallicity. However, B037 has a low metallicity to be $\rm [Fe/H]=-1.07\pm 0.20$. So, it seems improbable that the observed dust lane is physically associated with B037. It is clear that the origin of this dust lane is worthy of future study. In addition, based on these images, we present the precise variation of ellipticity and position angle, and of surface brightness profile, and determine the structural parameters of B037 by fitting a single-mass isotropic King model. In the F606W filter, we derive the best-fitting scale radius, r_0=0.56\pm0.02\arcsec~(=2.16\pm0.08~\rm{pc}), a tidal radius, r_t=8.6\pm0.4\arcsec~(=33.1\pm1.5~\rm{pc}), and a concentration index $c=\log (r_t/r_0)=1.19\pm0.02$. In the F814W filter, we derive r_0=0.56\pm0.01\arcsec~(=2.16\pm0.04~\rm{pc}), r_t=8.9\pm0.3\arcsec~(=34.3\pm1.2~\rm{pc}), and $c=\log (r_t/r_0)=1.20\pm0.01$. The extinction-corrected central surface brightness is $\mu_0=13.53\pm 0.03~{\rm mag~arcsec^{-2}}$ in the F606W filter, and $12.85\pm 0.03~{\rm mag~arcsec^{-2}}$ in the F814W filter, respectively.Comment: Accepted for Publication in RAA, 13 pages, 5 figures and 7 table

On the Wiener-Hopf solution of water-wave interaction with a submerged elastic or poroelastic plate.

A solution to the problem of water-wave scattering by a semi-infinite submerged thin elastic plate, which is either porous or non-porous, is presented using the Wiener-Hopf technique. The derivation of the Wiener-Hopf equation is rather different from that which is used traditionally in water-waves problems, and it leads to the required equations directly. It is also shown how the solution can be computed straightforwardly using Cauchy-type integrals, which avoids the need to find the roots of the highly non-trivial dispersion equations. We illustrate the method with some numerical computations, focusing on the evolution of an incident wave pulse which illustrates the existence of two transmitted waves in the submerged plate system. The effect of the porosity is studied, and it is shown to influence the shorter-wavelength pulse much more strongly than the longer-wavelength pulse

Age and structure parameters of a remote M31 globular cluster B514 based on HST, 2MASS, GALEX and BATC observations

B514 is a remote M31 globular cluster which locating at a projected distance of R_p~55 kpc. Deep observations with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST) are used to provide the accurate integrated light and star counts of B514. By coupling analysis of the distribution of the integrated light with star counts, we are able to reliably follow the profile of the cluster out to ~40". Based on the combined profile, we study in detail its surface brightness distribution in F606W and F814W filters, and determine its structural parameters by fitting a single-mass isotropic King model. The results showed that, the surface brightness distribution departs from the best-fit King model for r>10". B514 is quite flatted in the inner region, and has a larger half-light radius than majority of normal globular clusters of the same luminosity. It is interesting that, in the M_V versus log R_h plane, B514 lies nearly on the threshold for ordinary globular clusters as defined by Mackey & van den Bergh. In addition, B514 was observed as part of the Beijing-Arizona-Taiwan-Connecticut (BATC) Multicolor Sky Survey, using 13 intermediate-band filters covering a wavelength range of 3000--8500 \AA. Based on aperture photometry, we obtain its SEDs as defined by the 13 BATC filters. We determine the cluster's age and mass by comparing its SEDs (from 2267 to 20000{\AA}, comprising photometric data in the near-ultraviolet of GALEX, 5 SDSS bands, 13 BATC intermediate-band, and 2MASS near-infrared JHKs} filters) with theoretical stellar population synthesis models, resulting in age of $11.5\pm3.5$ Gyr. This age confirms the previous suggestion that B514 is an old GC in M31. B514 has a mass of $0.96-1.08 \times 10^6 \rm M_sun$, and is a medium-mass globular cluster in M31.Comment: Accepted for Publication in AJ, 18 pages, 6 figures and 9 table

Old stellar population synthesis: New age and mass estimates for Mayall II = G1

Mayall II = G1 is one of the most luminous globular clusters (GCs) in M31. Here, we determine its age and mass by comparing multicolor photometry with theoretical stellar population synthesis models. Based on far- and near-ultraviolet GALEX photometry, broad-band UBVRI, and infrared JHK_s 2MASS data, we construct the most extensive spectral energy distribution of G1 to date, spanning the wavelength range from 1538 to 20,000 A. A quantitative comparison with a variety of simple stellar population (SSP) models yields a mean age that is consistent with G1 being among the oldest building blocks of M31 and having formed within ~1.7 Gyr after the Big Bang. Irrespective of the SSP model or stellar initial mass function adopted, the resulting mass estimates (of order $10^7 M_\odot$) indicate that G1 is one of the most massive GCs in the Local Group. However, we speculate that the cluster's exceptionally high mass suggests that it may not be a genuine GC. We also derive that G1 may contain, on average, $(1.65\pm0.63)\times10^2 L_\odot$ far-ultraviolet-bright, hot, extreme horizontal-branch stars, depending on the SSP model adopted. On a generic level, we demonstrate that extensive multi-passband photometry coupled with SSP analysis enables one to obtain age estimates for old SSPs to a similar accuracy as from integrated spectroscopy or resolved stellar photometry, provided that some of the free parameters can be constrained independently.Comment: Accepted for Publication in RAA, 12 pages, 1 figure, 2 table

TL1A/DR3 axis involvement in the inflammatory cytokine network during pulmonary sarcoidosis

BACKGROUND: TNF-like ligand 1A (TL1A), a recently recognized member of the TNF superfamily, and its death domain receptor 3 (DR3), firstly identified for their relevant role in T lymphocyte homeostasis, are now well-known mediators of several immune-inflammatory diseases, ranging from rheumatoid arthritis to inflammatory bowel diseases to psoriasis, whereas no data are available on their involvement in sarcoidosis, a multisystemic granulomatous disease where a deregulated T helper (Th)1/Th17 response takes place. METHODS: In this study, by flow cytometry, real-time PCR, confocal microscopy and immunohistochemistry analyses, TL1A and DR3 were investigated in the pulmonary cells and the peripheral blood of 43 patients affected by sarcoidosis in different phases of the disease (29 patients with active sarcoidosis, 14 with the inactive form) and in 8 control subjects. RESULTS: Our results demonstrated a significant higher expression, both at protein and mRNA levels, of TL1A and DR3 in pulmonary T cells and alveolar macrophages of patients with active sarcoidosis as compared to patients with the inactive form of the disease and to controls. In patients with sarcoidosis TL1A was strongly more expressed in the lung than the blood, i.e., at the site of the involved organ. Additionally, zymography assays showed that TL1A is able to increase the production of matrix metalloproteinase 9 by sarcoid alveolar macrophages characterized, in patients with the active form of the disease, by reduced mRNA levels of the tissue inhibitor of metalloproteinase (TIMP)-1. CONCLUSIONS: These data suggest that TL1A/DR3 interactions are part of the extended and complex immune-inflammatory network that characterizes sarcoidosis during its active phase and may contribute to the pathogenesis and to the progression of the disease

A "super" star cluster grown old: the most massive star cluster in the Local Group

We independently redetermine the reddening and age of the globular cluster 037-B327 in M31 by comparing independently obtained multicolour photometry with theoretical stellar population synthesis models. 037-B327 has long been known to have a very large reddening value, which we confirm to be E(B-V)=1.360+-0.013, in good agreement with the previous results. We redetermine its most likely age at 12.4+- 3.2 Gyr. 037-B327 is a prime example of an unusually bright early counterpart to the ubiquitous ``super'' star clusters presently observed in most high-intensity star-forming regions in the local Universe. In order to have survived for a Hubble time, we conclude that its stellar IMF cannot have been top-heavy. Using this constraint, and a variety of SSP models, we determine a photometric mass of M_{GC}=(3.0+-0.5)*10^7, somewhat depending on the SSP models used, the metallicity and age adopted and the IMF representation. This mass, and its relatively small uncertainties, make this object the most massive star cluster of any age in the Local Group. Assuming that the photometric mass estimate thus derived is fairly close to its dynamical mass, we predict that this GC has a (one-dimensional) velocity dispersion of order (72+-13)km/s. As a surviving "super" star cluster, this object is of prime importance for theories aimed at describing massive star cluster evolution.Comment: Accepted for Publication in MNRAS, 8 pages, 4 figure

Detection of IMBHs from microlensing in globular clusters

Globular clusters have been alternatively predicted to host intermediate-mass black holes (IMBHs) or nearly impossible to form and retain them in their centres. Over the last decade enough theoretical and observational evidence have accumulated to believe that many galactic globular clusters may host IMBHs in their centres, just like galaxies do. The well-established correlations between the supermassive black holes and their host galaxies do suggest that, in extrapolation, globular clusters (GCs) follow the same relations. Most of the attempts in search of the central black holes (BHs) are not direct and present enormous observational difficulties due to the crowding of stars in the GC cores. Here we propose a new method of detection of the central BH -- the microlensing of the cluster stars by the central BH. If the core of the cluster is resolved, the direct determination of the lensing curve and lensing system parameters are possible; if unresolved, the differential imaging technique can be applied. We calculate the optical depth to central BH microlensing for a selected list of Galactic GCs and estimate the average time duration of the events. We present the observational strategy and discuss the detectability of microlensing events using a 2-m class telescope.Comment: 10 pages, 11 figures, accepted in New Astronom

RIP4 inhibits STAT3 signaling to sustain lung adenocarcinoma differentiation.

Loss of epithelial differentiation and extracellular matrix (ECM) remodeling are known to facilitate cancer progression and are associated with poor prognosis in patients with lung cancer. We have identified Receptor-interacting serine/threonine protein kinase 4 (RIP4) as a regulator of tumor differentiation in lung adenocarcinoma (AC). Bioinformatics analyses of human lung AC samples showed that poorly differentiated tumors express low levels of RIP4, whereas high levels are associated with better overall survival. In vitro, lung tumor cells expressing reduced RIP4 levels showed enhanced activation of STAT3 signaling and had a greater ability to invade through collagen. In contrast, overexpression of RIP4 inhibited STAT3 activation, which abrogated interleukin-6-dependent induction of lysyl oxidase, a collagen cross-linking enzyme. In an autochthonous mouse model of lung AC initiated by Kras(G12D) expression with loss of p53, Rip4 knockdown tumors progressed to a poorly differentiated state marked by an increase in Hmga2, reduced Ttf1, and enrichment of genes regulating extracellular remodeling and Jak-Stat signaling. Tail vein injections of cells overexpressing Rip4 showed a reduced potential to invade and form tumors, which was restored by co-expression of Stat3. Altogether, our work has identified that loss of RIP4 enhances STAT3 signaling in lung cancer cells, promoting the expression of ECM remodeling genes and cancer dedifferentiation

HST/ACS color-magnitude diagrams of candidate intermediate-age M 31 globular clusters. The role of blue horizontal branches

We present deep (V ~ 28.0) BV photometry obtained with the wide field channel of the Advanced Camera for Surveys on board HST for four M31 globular clusters that were identified as candidate intermediate-age (age ~ 1-9 Gyr) by various authors, based on their integrated spectra and/or broad/intermediate-band colors. Two of them (B292 and B350) display an obvious blue horizontal branch, indicating that they are as old as the oldest Galactic globulars. On the other hand, for the other two (B058 and B337), which display red horizontal branches, it was not possible either to confirm or disconfirm the age estimate from integrated spectra. The analysis of the distribution in the spectral indices Mg2 and H_beta of the M31 and Milky Way clusters whose horizontal branch can be classified as red or blue based on existing CMDs, strongly suggests that classical age diagnostics from integrated spectra may be significantly influenced by the HB morphology of the clusters and can lead to erroneous age-classifications. We also provide the CMD for another two clusters that fall into the field of the main targets, B336, an old and metal-poor globular with a significant population of RR-Lyrae variables, and the newly discovered B531, a cluster with a very red red giant branch.Comment: Accepted for publication in Astronomy and Astrophysics; 13 pages, 13 figures and 7 tables. Some figures have been decreased in quality, an higher resolution version is available at http://www.bo.astro.it/M31/hstcatalog