A Survey of Irradiated Pillars, Globules, and Jets in the Carina Nebul

We present wide-field, deep narrowband H$_2$, Br$\gamma$, H$\alpha$, [S II], [O III], and broadband I and K-band images of the Carina star formation region. The new images provide a large-scale overview of all the H$_2$ and Br$\gamma$ emission present in over a square degree centered on this signature star forming complex. By comparing these images with archival HST and Spitzer images we observe how intense UV radiation from O and B stars affects star formation in molecular clouds. We use the images to locate new candidate outflows and identify the principal shock waves and irradiated interfaces within dozens of distinct areas of star-forming activity. Shocked molecular gas in jets traces the parts of the flow that are most shielded from the intense UV radiation. Combining the H$_2$ and optical images gives a more complete view of the jets, which are sometimes only visible in H$_2$. The Carina region hosts several compact young clusters, and the gas within these clusters is affected by radiation from both the cluster stars and the massive stars nearby. The Carina Nebula is ideal for studying the physics of young H II regions and PDR's, as it contains multiple examples of walls and irradiated pillars at various stages of development. Some of the pillars have detached from their host molecular clouds to form proplyds. Fluorescent H$_2$ outlines the interfaces between the ionized and molecular gas, and after removing continuum, we detect spatial offsets between the Br$\gamma$ and H$_2$ emission along the irradiated interfaces. These spatial offsets can be used to test current models of PDRs once synthetic maps of these lines become available.Comment: Accepted in the Astronomical Journa

MAP: Microblogging Assisted Profiling of TV Shows

Online microblogging services that have been increasingly used by people to share and exchange information, have emerged as a promising way to profiling multimedia contents, in a sense to provide users a socialized abstraction and understanding of these contents. In this paper, we propose a microblogging profiling framework, to provide a social demonstration of TV shows. Challenges for this study lie in two folds: First, TV shows are generally offline, i.e., most of them are not originally from the Internet, and we need to create a connection between these TV shows with online microblogging services; Second, contents in a microblogging service are extremely noisy for video profiling, and we need to strategically retrieve the most related information for the TV show profiling.To address these challenges, we propose a MAP, a microblogging-assisted profiling framework, with contributions as follows: i) We propose a joint user and content retrieval scheme, which uses information about both actors and topics of a TV show to retrieve related microblogs; ii) We propose a social-aware profiling strategy, which profiles a video according to not only its content, but also the social relationship of its microblogging users and its propagation in the social network; iii) We present some interesting analysis, based on our framework to profile real-world TV shows

Museum material reveals a frog parasite emergence after the invasion of the cane toad in Australia

<p>Abstract</p> <p>Background</p> <p>A parasite morphologically indistinguishable from <it>Myxidium immersum </it>(Myxozoa: Myxosporea) found in gallbladders of the invasive cane toad (<it>Bufo marinus</it>) was identified in Australian frogs. Because no written record exists for such a parasite in Australian endemic frogs in 19^thand early 20^thcentury, it was assumed that the cane toad introduced this parasite. While we cannot go back in time ourselves, we investigated whether material at the museum of natural history could be used to retrieve parasites, and whether they were infected at the time of their collection (specifically prior to and after the cane toad translocation to Australia in 1935).</p> <p>Results</p> <p>Using the herpetological collection at the Australian Museum we showed that no myxospores were found in any animals (<it>n </it>= 115) prior to the cane toad invasion (1879-1935). The green and golden bell frog (<it>Litoria aurea</it>), the Peron's tree frog (<it>Litoria peronii</it>), the green tree frog (<it>Litoria caerulea</it>) and the striped marsh frog (<it>Limnodynastes peronii</it>) were all negative for the presence of the parasite using microscopy of the gallbladder content and its histology. These results were sufficient to conclude that the population was free from this disease (at the expected minimum prevalence of 5%) at 99.7% confidence level using the 115 voucher specimens in the Australian Museum. Similarly, museum specimens (<it>n </it>= 29) of the green and golden bell frog from New Caledonia, where it was introduced in 19^thcentury, did not show the presence of myxospores. The earliest specimen positive for myxospores in a gallbladder was a green tree frog from 1966. Myxospores were found in eight (7.1%, <it>n </it>= 112) frogs in the post cane toad introduction period.</p> <p>Conclusion</p> <p>Australian wildlife is increasingly under threat, and amphibian decline is one of the most dramatic examples. The museum material proved essential to directly support the evidence of parasite emergence in Australian native frogs. This parasite can be considered one of the luckiest parasites, because it has found an empty niche in Australia. It now flourishes in > 20 endemic and exotic frog species, but its consequences are yet to be fully understood.</p

Unsupervised Learning with Normalised Data and Non-Euclidean Norms

Peer reviewe

Reopening the TNOs Color Controversy: Centaurs Bimodality and TNOs Unimodality

We revisit the Trans-Neptunian Objects (TNOs) color controversy allegedly solved by Tegler and Romanishin 2003. We debate the statistical approach of the quoted work and discuss why it can not draw the claimed conclusions, and reanalyze their data sample with a more adequate statistical test. We find evidence for the existence of two color groups among the Centaurs. Therefore, mixing both centaurs and TNOs populations lead to the erroneous conclusion of a global bimodality, while there is no evidence for two color groups in the TNOs population alone. We use quasi-simultaneous visible color measurements published for 20 centaurs (corresponding to about half of the identified objects of this class), and conclude on the existence of two groups. With the surface evolution model of Delsanti et al. (2003) we discuss how the existence of two groups of Centaurs may be compatible with a continuous TNOs color distribution.Comment: 4 pages, 4 figures, accepted for publication in Astronomy and Astrophysics Letter

Two-component jet simulations: I. Topological stability of analytical MHD outflow solutions

Observations of collimated outflows in young stellar objects indicate that several features of the jets can be understood by adopting the picture of a two-component outflow, wherein a central stellar component around the jet axis is surrounded by an extended disk-wind. The precise contribution of each component may depend on the intrinsic physical properties of the YSO-disk system as well as its evolutionary stage. In this context, the present article starts a systematic investigation of two-component jet models via time-dependent simulations of two prototypical and complementary analytical solutions, each closely related to the properties of stellar-outflows and disk-winds. These models describe a meridionally and a radially self-similar exact solution of the steady-state, ideal hydromagnetic equations, respectively. By using the PLUTO code to carry out the simulations, the study focuses on the topological stability of each of the two analytical solutions, which are successfully extended to all space by removing their singularities. In addition, their behavior and robustness over several physical and numerical modifications is extensively examined. It is found that radially self-similar solutions (disk-winds) always reach a final steady-state while maintaining all their well-defined properties. The different ways to replace the singular part of the solution around the symmetry axis, being a first approximation towards a two-component outflow, lead to the appearance of a shock at the super-fast domain corresponding to the fast magnetosonic separatrix surface. Conversely, the asymptotic configuration and the stability of meridionally self-similar models (stellar-winds) is related to the heating processes at the base of the wind.Comment: Accepted for publication in A&

Asymptotic Learning Curve and Renormalizable Condition in Statistical Learning Theory

Bayes statistics and statistical physics have the common mathematical structure, where the log likelihood function corresponds to the random Hamiltonian. Recently, it was discovered that the asymptotic learning curves in Bayes estimation are subject to a universal law, even if the log likelihood function can not be approximated by any quadratic form. However, it is left unknown what mathematical property ensures such a universal law. In this paper, we define a renormalizable condition of the statistical estimation problem, and show that, under such a condition, the asymptotic learning curves are ensured to be subject to the universal law, even if the true distribution is unrealizable and singular for a statistical model. Also we study a nonrenormalizable case, in which the learning curves have the different asymptotic behaviors from the universal law

A Candidate Young Massive Planet in Orbit around the Classical T Tauri Star CI Tau

The ~2 Myr old classical T Tauri star CI Tau shows periodic variability in its radial velocity (RV) variations measured at infrared (IR) and optical wavelengths. We find that these observations are consistent with a massive planet in a ~9-day period orbit. These results are based on 71 IR RV measurements of this system obtained over 5 years, and on 26 optical RV measurements obtained over 9 years. CI Tau was also observed photometrically in the optical on 34 nights over ~one month in 2012. The optical RV data alone are inadequate to identify an orbital period, likely the result of star spot and activity induced noise for this relatively small dataset. The infrared RV measurements reveal significant periodicity at ~9 days. In addition, the full set of optical and IR RV measurements taken together phase coherently and with equal amplitudes to the ~9 day period. Periodic radial velocity signals can in principle be produced by cool spots, hot spots, and reflection of the stellar spectrum off the inner disk, in addition to resulting from a planetary companion. We have considered each of these and find the planet hypothesis most consistent with the data. The radial velocity amplitude yields an Msin(i) of ~8.1 M_Jup; in conjunction with a 1.3 mm continuum emission measurement of the circumstellar disk inclination from the literature, we find a planet mass of ~11.3 M_Jup, assuming alignment of the planetary orbit with the disk.Comment: 61 pages, 13 figures, accepted for publication in The Astrophysical Journa

On the Nature of Soft X-ray Weak Quasi-Stellar Objects

Recent studies of QSOs with ROSAT suggest the existence of a significant population of Soft X-ray Weak QSOs (SXW QSOs) where the soft X-ray flux is ~ 10-30 times smaller than in typical QSOs. As a first step in a systematic study of these objects, we establish a well-defined sample of SXW QSOs which includes all alpha_ox<=-2 QSOs from the Boroson & Green (1992) sample of 87 BQS QSOs. SXW QSOs comprise about 11% of this optically selected QSO sample. From an analysis of CIV absorption in the 55 BG92 QSOs with available CIV data, we find a remarkably strong correlation between alpha_ox and the CIV absorption equivalent width. This correlation suggests that absorption is the primary cause of soft X-ray weakness in QSOs, and it reveals a continuum of absorption properties connecting unabsorbed QSOs, X-ray warm absorber QSOs, SXW QSOs and BAL QSOs. From a practical point of view, our correlation demonstrates that selection by soft X-ray weakness is an effective (>=80% successful) and observationally inexpensive way to find low-redshift QSOs with strong and interesting ultraviolet absorption. We have also identified several notable differences between the optical emission-line properties of SXW QSOs and those of the other BG92 QSOs. SXW QSOs show systematically low [O III] luminosities as well as distinctive H-beta profiles. They tend to lie toward the weak-[O III] end of BG92 eigenvector 1, as do many low-ionization BAL QSOs. Unabsorbed Seyferts and QSOs with similar values of eigenvector 1 have been suggested to have extreme values of a primary physical parameter, perhaps mass accretion rate relative to the Eddington rate (M-dot/M-dot_{Edd}). If these suggestions are correct, it is likely that SXW QSOs also tend to have generally high values of (M-dot/M-dot_{Edd}). (Abridged)Comment: 34 pages, ApJ accepted, also available from http://www.astro.psu.edu/users/niel/papers/papers.htm