Submm-bright QSOs at z~2: signposts of co-evolution at high z

We have assembled a sample of 5 X-ray and submm-luminous z~2 QSOs which are therefore both growing their central black holes through accretion and forming stars copiously at a critical epoch. Hence, they are good laboratories to investigate the co-evolution of star formation and AGN. We have performed a preliminary analysis of the AGN and SF contributions to their UV-to-FIR SEDs, fitting them with simple direct (disk), reprocessed (torus) and star formation components. All three are required by the data and hence we confirm that these objects are undergoing strong star formation in their host galaxies at rates 500-2000 Msun/y. Estimates of their covering factors are between about 30 and 90%. In the future, we will assess the dependence of these results on the particular models used for the components and relate their observed properties to the intrinsice of the central engine and the SF material, as well as their relevance for AGN-galaxy coevolution.Comment: 6 pages, 2 figures, contributed talk to "Nuclei of Seyfert galaxies and QSOs - Central engine & conditions of star formation" November 6-8, 2012. MPIfR, Bonn, Germany. Po

Submm-bright X-ray absorbed QSOs at z~2: insights into the co-evolution of AGN and star-formation

We have assembled a sample of 5 X-ray-absorbed and submm-luminous type 1 QSOs at $z \sim 2$ which are simultaneously growing their central black holes through accretion and forming stars copiously. We present here the analysis of their rest-frame UV to submm Spectral Energy Distributions (SEDs), including new Herschel data. Both AGN (direct and reprocessed) and Star Formation (SF) emission are needed to model their SEDs. From the SEDs and their UV-optical spectra we have estimated the masses of their black holes $M_{BH}\sim 10^{9}-10^{10}\,M_{\odot}$, their intrinsic AGN bolometric luminosities $L_{BOL}\sim(0.8 - 20)\times 10^{13} L_{\odot}$, Eddington ratios $L_{BOL}/L_{Edd}\sim 0.1 - 1.1$ and bolometric corrections $L_{BOL}/L_{X,2-10}\sim 30 - 500$. These values are common among optically and X-ray-selected type 1 QSOs (except for RX~J1249), except for the bolometric corrections, which are higher. These objects show very high far-infrared luminosities $L_{FIR}\sim$ (2 - 8)$\times10^{12}\,M_{\odot}$ and Star Formation Rates SFR$\sim 1000 M_{\odot}/$y. From their $L_{FIR}$ and the shape of their FIR-submm emission we have estimated star-forming dust masses of $M_{DUST}\sim 10^9\,M_\odot$. We have found evidence of a tentative correlation between the gas column densities of the ionized absorbers detected in X-ray (N$_{H_{ion}}$) and $SFR$. Our computed black hole masses are amongst the most massive known.Comment: Accepted for publication in MNRAS, December 22, 2014, 17 pages, 5 figure

Covariance forecasting in equity markets

We compare the performance of popular covariance forecasting models in the context of a portfolio of major European equity indices. We find that models based on high-frequency data offer a clear advantage in terms of statistical accuracy. They also yield more theoretically consistent predictions from an empirical asset pricing perspective, and, lead to superior out-of-sample portfolio performance. Overall, a parsimonious Vector Heterogeneous Autoregressive (VHAR) model that involves lagged daily, weekly and monthly realised covariances achieves the best performance out of the competing models. A promising new simple hybrid covariance estimator is developed that exploits option-implied information and high-frequency data while adjusting for the volatility riskpremium. Relative model performance does not change during the global financial crisis, or, if a different forecast horizon, or, intraday sampling frequency is employed. Finally, our evidence remains robust when we consider an alternative sample of U.S. stocks

Herschel/HerMES: the X-ray–infrared correlation for star-forming galaxies at z ~ 1

For the first time, we investigate the X-ray/infrared (IR) correlation for star-forming galaxies (SFGs) at z ~ 1, using SPIRE submm data from the recently launched Herschel Space Observatory and deep X-ray data from the 2-Ms Chandra Deep Field-North survey. We examine the X-ray/IR correlation in the soft X-ray (SX; 0.5–2 keV) and hard X-ray (HX; 2–10 keV) bands by comparing our z ~ 1 SPIRE-detected SFGs to equivalently IR-luminous (L_(IR) > 10^(10) L_⊙) samples in the local/low-redshift Universe. Our results suggest that the X-ray/IR properties of the SPIRE SFGs are on average similar to those of their local counterparts, as we find no evidence for evolution in the L_(SX)/L_(IR) and L_(HX)/L_(IR) ratios with redshift. We note, however, that at all redshifts, both L_(SX)/L_(IR) and L_(HX)/L_(IR) are strongly dependent on IR luminosity, with luminous and ultraluminous IR galaxies (LIRGs and ULIRGs; L_(IR) > 10^(11) L_⊙) having up to an order of magnitude lower values than normal IR galaxies (L_(IR) < 10^(11) L_⊙). We derive a L_(SX)–L_(IR) relation and confirm the applicability of an existing L_(HX)–L_(IR) relation for both local and distant LIRGs and ULIRGs, consistent with a scenario where X-ray luminosity is correlated with the star formation rate

Local Guarantees in Graph Cuts and Clustering

Correlation Clustering is an elegant model that captures fundamental graph cut problems such as Min $s-t$ Cut, Multiway Cut, and Multicut, extensively studied in combinatorial optimization. Here, we are given a graph with edges labeled $+$ or $-$ and the goal is to produce a clustering that agrees with the labels as much as possible: $+$ edges within clusters and $-$ edges across clusters. The classical approach towards Correlation Clustering (and other graph cut problems) is to optimize a global objective. We depart from this and study local objectives: minimizing the maximum number of disagreements for edges incident on a single node, and the analogous max min agreements objective. This naturally gives rise to a family of basic min-max graph cut problems. A prototypical representative is Min Max $s-t$ Cut: find an $s-t$ cut minimizing the largest number of cut edges incident on any node. We present the following results: $(1)$ an $O(\sqrt{n})$-approximation for the problem of minimizing the maximum total weight of disagreement edges incident on any node (thus providing the first known approximation for the above family of min-max graph cut problems), $(2)$ a remarkably simple $7$-approximation for minimizing local disagreements in complete graphs (improving upon the previous best known approximation of $48$), and $(3)$ a $1/(2+\varepsilon)$-approximation for maximizing the minimum total weight of agreement edges incident on any node, hence improving upon the $1/(4+\varepsilon)$-approximation that follows from the study of approximate pure Nash equilibria in cut and party affiliation games

Central Serous Chorioretinopathy with Subretinal Deposition of Fibrin-Like Material and Its Prompt Response to Ranibizumab Injections

Purpose: Central serous chorioretinopathy (CSCR) manifests as neurosensory detachment of the macula and can be attributed to focal or multifocal leakage in the retinal pigment epithelium (RPE). Fibrin accumulation in the subretinal space is an unusual and heretofore unreported visually damaging manifestation of severe CSCR. Methods: The patient was followed up with the use of biomicroscopy, fluorescein angiography, and optical coherence tomography (OCT). Results: A 32-year-old woman was referred to our department complaining of metamorphopsia and decreased visual acuity in the right eye. Best-corrected visual acuity (BCVA) was 20/40 in the right eye and 20/20 in the left eye. Biomicroscopy revealed an irregularly shaped foveal elevation and wrinkling in the right eye. OCT showed a steep neurosensory retina elevation with a highly reflective material accumulation in the subretinal space, presumably fibrin. Our diagnosis was CSCR complicated by subretinal fibrin accumulation. Since most of these cases resolve spontaneously, the patient was kept under observation; 1 month later, the fibrin accumulation had expanded subfoveally (BCVA 20/200). The patient was offered 3 intravitreal ranibizumab injections. After the initial injection, BCVA improved to 20/50 and, after the 3 injections, to 20/30. Two months later (BCVA 20/30), fresh leakage was observed at the margin of the original lesion, and an additional intravitreal ranibizumab injection was performed. After another 2 months, BCVA stabilized at 20/25 and remained stable throughout the 12 months after the initial injection. Conclusions: Prompt recognition of CSCR complicated by subretinal fibrin and immediate intervention may result in recovery from this potentially devastating complication. Ranibizumab may be an alternative treatment option in the management of refractory CSCR complicated by subretinal fibrin accumulation

Peripapillary Neovascular Membrane in a Young Pregnant Woman and Prompt Response to Ranibizumab Injections following Uneventful Delivery

Purpose: Occurrence of choroidal neovascularization (CNV) during pregnancy has been reported as a complication of presumed ocular histoplasmosis syndrome or punctuate inner chorioretinopathy. To our knowledge, idiopathic CNV (ICNV) during pregnancy has only been reported once in the relevant literature. Bevacizumab has been used for the treatment of ICNV in small case series. However, there is limited experience regarding the use of ranibizumab for the management of ICNV. Case Report: A 31-year-old woman in the eighth month of her second pregnancy was diagnosed with mild macular and papillary edema. She was followed up using biomicroscopy, fluorescein angiography (FA), and optical coherence tomography (OCT). After 3 months, visual acuity further deteriorated and funduscopy, FA and OCT findings revealed a juxtapapillary choroidal neovascular membrane (CNVM). After two ranibizumab injections, best-corrected visual acuity increased significantly, physiological macular anatomy was restored and no subretinal fluid was observed. Discussion: In this case report, we present a young pregnant patient with peripapillary ICNV and neurosensory detachment involving the macula, and treatment of the eye with intravitreal ranibizumab following uneventful delivery. Increased angiogenic factor levels associated with pregnancy may contribute to the onset of CNV although this relationship has to be investigated experimentally. The rapid response to ranibizumab suggests that this anti-VEGF agent may be an alternative treatment option in the management of peripapillary ICNV

HERMES: Scalable, Secure, and Privacy-Enhancing Vehicle Access System

We propose HERMES, a scalable, secure, and privacy-enhancing system for users to share and access vehicles. HERMES securely outsources operations of vehicle access token generation to a set of untrusted servers. It builds on an earlier proposal, namely SePCAR [1], and extends the system design for improved efficiency and scalability. To cater to system and user needs for secure and private computations, HERMES utilizes and combines several cryptographic primitives with secure multiparty computation efficiently. It conceals secret keys of vehicles and transaction details from the servers, including vehicle booking details, access token information, and user and vehicle identities. It also provides user accountability in case of disputes. Besides, we provide semantic security analysis and prove that HERMES meets its security and privacy requirements. Last but not least, we demonstrate that HERMES is efficient and, in contrast to SePCAR, scales to a large number of users and vehicles, making it practical for real-world deployments. We build our evaluations with two different multiparty computation protocols: HtMAC-MiMC and CBC-MAC-AES. Our results demonstrate that HERMES with HtMAC-MiMC requires only approx 1,83 ms for generating an access token for a single-vehicle owner and approx 11,9 ms for a large branch of rental companies with over a thousand vehicles. It handles 546 and 84 access token generations per second, respectively. This results in HERMES being 696 (with HtMAC-MiMC) and 42 (with CBC-MAC-AES) times faster compared to in SePCAR for a single-vehicle owner access token generation. Furthermore, we show that HERMES is practical on the vehicle side, too, as access token operations performed on a prototype vehicle on-board unit take only approx 62,087 ms