39 research outputs found
A Wide Field, Low Frequency Radio Survey of the Field of M31: I. Construction and Statistical Analysis of the Source Catalog
We present here the results of a 325 MHz radio survey of M31, conducted with
the A-configuration of the Very Large Array. The survey covered an area of 7.6
deg, and a total of 405 radio sources between \la6\arcsec and 170\arcsec
in extent were mapped with a resolution of 6\arcsec and a 1 sensitivity
of 0.6 \mjyb. For each source, its morphological class, major axis
, minor axis , position angle , peak flux ,
integrated flux density , spectral index and spectral curvature
parameter were calculated. A comparison of the flux and radial
distribution -- both in the plane of the sky and in the plane of M31 -- of
these sources with those of the XMM--LSS and WENSS radio surveys revealed that
a vast majority of sources detected are background radio galaxies. As a result
of this analysis, we expect that only a few sources are intrinsic to M31. These
sources are identified and discussed in an accompanying paper.Comment: 29 pages with 4 tables and 10 figures (JPEGs), accepted for
publication in ApJS. Full-resolution images available on reques
The Herschel Exploitation of Local Galaxy Andromeda (HELGA). VI. The distribution and properties of molecular cloud associations in M31
In this paper we present a catalog of Giant Molecular Clouds (GMCs) in the An- dromeda (M31) galaxy extracted from the Herschel Exploitation of Local Galaxy An- dromeda (HELGA) dataset. GMCs are identified from the Herschel maps using a hierarchical source extraction algorithm. We present the results of this new catalog and characterise the spatial distribution and spectral energy properties of its clouds based on the radial dust/gas properties found by Smith et al (2012). 326 GMCs in the mass range 104 − 107 M⊙ are identified, their cumulative mass distribution is found to be proportional to M −2.34 in agreement with earlier studies. The GMCs appear to follow the same cloud mass to LCO correlation observed in the Milky Way. However, comparison between this catalog and interferometry studies also shows that the GMCs are substructured below the Herschel resolution limit suggesting that we are observing associations of GMCs. Following Gordon et al. (2006), we study the spatial structure of M31 by splitting the observed structure into a set of spiral arms and offset rings. We fit radii of 10.3 and 15.5 kpc to the two most prominent rings. We then fit a logarithmic spiral with a pitch angle of 8fdg9 to the GMCs not associated with either ring. Last, we comment on the effects of deprojection on our results and investigate the effect different models for M31's inclination will have on the projection of an unperturbed spiral arm system
The X-ray Transient 2XMMi J003833.3+402133: A Candidate Magnetar at High Galactic Latitude
We present detailed analysis of the transient X-ray source 2XMMi
J003833.3+402133 detected by XMM-Newton in January 2008 during a survey of M
31. The X-ray spectrum is well fitted by either a steep power law plus a
blackbody model or a double blackbody model. Prior observations with
XMM-Newton, Chandra, Swift and ROSAT spanning 1991 to 2007, as well as an
additional Swift observation in 2011, all failed to detect this source. No
counterpart was detected in deep optical imaging with the Canada France Hawaii
Telescope down to a 3sigma lower limit of g = 26.5 mag. This source has
previously been identified as a black hole X-ray binary in M 31. While this
remains a possibility, the transient behaviour, X-ray spectrum, and lack of an
optical counterpart are equally consistent with a magnetar interpretation for
2XMMi J003833.3+402133. The derived luminosity and blackbody emitting radius at
the distance of M 31 argue against an extragalactic location, implying that if
it is indeed a magnetar it is located within the Milky Way but 22deg out of the
plane. The high Galactic latitude could be explained if 2XMMi J003833.3+402133
were an old magnetar, or if its progenitor was a runaway star that traveled
away from the plane prior to going supernova.Comment: 16 pages, 5 figures, 4 tables, accepted for publication in ApJ
following moderate revisio
A Wide Field, Low Frequency Radio Image of the Field of M31: II. -- Source Classification and Discussion
We have previously presented the results of a 325 MHz radio survey of M31,
conducted with the A-configuration of the Very Large Array. In this survey, a
total of 405 radio sources between <6" and 170" in extent were mapped with a
resolution of 6" and a sensitivity of ~0.6 mJy/beam. Here, we compare the
resultant source list and image with other radio, IR, optical, X-ray
observations and catalogs of the region. Through this, we were able to identify
five supernova remnant (SNR) candidates and three pulsar wind nebula (PWN)
candidates in M31, as well as three Milky Way radio stars, a possible Milky Way
Planetary Nebula, and a bevy of interesting extragalactic objects: a BL Lac, a
Giant Radio Galaxy, a galaxy merger, and several high-z radio galaxy
candidates. In addition, a large number of compact (<6") extremely steep
spectrum sources () were
detected whose nature is unknown.Comment: 30 pages, 23 tables, + 18 figures. Low-resolution figures are
available here in .jpg form. ApJS accepted, to be published in August 2005,
v159 2 issu
Unwanted effects: Is there a negative side of meditation? A multicentre survey
Objectives Despite the long-term use and evidence-based efficacy of meditation and mindfulness-based interventions, there is still a lack of data about the possible unwanted effects (UEs) of these practices. The aim of this study was to evaluate the occurrence of UEs among meditation practitioners, considering moderating factors such as the type, frequency, and lifetime duration of the meditation practices. Methods An online survey was developed and disseminated through several websites, such as Spanish-, English- and Portuguese-language scientific research portals related to mindfulness and meditation. After excluding people who did not answer the survey correctly or completely and those who had less than two months of meditation experience, a total of 342 people participated in the study. However, only 87 reported information about UEs. Results The majority of the practitioners were women from Spain who were married and had a University education level. Practices were more frequently informal, performed on a daily basis, and followed by focused attention (FA). Among the participants, 25.4% reported UEs, showing that severity varies considerably. The information requested indicated that most of the UEs were transitory and did not lead to discontinuing meditation practice or the need for medical assistance. They were more frequently reported in relation to individual practice, during focused attention meditation, and when practising for more than 20 minutes and alone. The practice of body awareness was associated with UEs to a lesser extent, whereas focused attention was associated more with UEs. Conclusions This is the first large-scale, multi-cultural study on the UEs of meditation. Despite its limitations, this study suggests that UEs are prevalent and transitory and should be further studied. We recommend the use of standardized questionnaires to assess the UEs of meditation practices
Methanotrophy, Methylotrophy, the Human Body and Disease
Methylotrophic Bacteria use one-carbon (C1) compounds as their carbon source. They have been known to be associated to the human body for almost 20 years as part of the normal flora and were identified as pathogens in the early 1990s in end-stage HIV patients and chemotherapy patients. In this chapter, I look at C1 compounds in the human body and exposure from the environment and then consider Methylobacterium spp. and Methylorubrum spp. in terms of infections, its role in breast and bowel cancers; Methylococcus capsulatus and its role in inflammatory bowel disease, and Brevibacterium casei and Hyphomicrobium sulfonivorans as part of the normal human flora. I also consider the abundance of methylotrophs from the Actinobacteria being identified in human studies and the potential bias of the ionic strength of culture media and the needs for future work. Within the scope of future work, I consider the need for the urgent assessment of the pathogenic, oncogenic, mutagenic and teratogenic potential of Methylobacterium spp. and Methylorubrum spp. and the need to handle them at higher containment levels until more data are available