23 research outputs found
Shocked similarity collapses and flows in star formation processes
We propose self-similar shocked flow models for certain dynamical evolution
phases of young stellar objects (YSOs), `champagne flows' of H {\sevenrm II}
regions surrounding OB stars and shaping processes of planetary nebulae (PNe).
We analyze an isothermal fluid of spherical symmetry and construct families of
similarity shocked flow solutions featured by: 1. either a core expansion with
a finite central density or a core accretion at constant rate with a density
scaling ; 2. a shock moving outward at a constant speed; 3. a
preshock gas approaching a constant speed at large with a density scaling
. In addition to testing numerical codes, our models can
accommodate diverse shocked flows with or without a core collapse or outflow
and an envelope expansion or contraction. As an application, we introduce our
model analysis to observations of Bok globule B335.Comment: ApJL accepte
The effects of spatial resolution on Integral Field Spectrograph surveys at different redshifts. The CALIFA perspective
Over the past decade, 3D optical spectroscopy has become the preferred tool
for understanding the properties of galaxies and is now increasingly used to
carry out galaxy surveys. Low redshift surveys include SAURON, DiskMass,
ATLAS3D, PINGS and VENGA. At redshifts above 0.7, surveys such as MASSIV, SINS,
GLACE, and IMAGES have targeted the most luminous galaxies to study mainly
their kinematic properties. The on-going CALIFA survey () is the
first of a series of upcoming Integral Field Spectroscopy (IFS) surveys with
large samples representative of the entire population of galaxies. Others
include SAMI and MaNGA at lower redshift and the upcoming KMOS surveys at
higher redshift. Given the importance of spatial scales in IFS surveys, the
study of the effects of spatial resolution on the recovered parameters becomes
important. We explore the capability of the CALIFA survey and a hypothetical
higher redshift survey to reproduce the properties of a sample of objects
observed with better spatial resolution at lower redshift. Using a sample of
PINGS galaxies, we simulate observations at different redshifts. We then study
the behaviour of different parameters as the spatial resolution degrades with
increasing redshift.Comment: 20 pages, 16 figures. Accepted for publication in A&
Counting function fluctuations and extreme value threshold in multifractal patterns: the case study of an ideal noise
To understand the sample-to-sample fluctuations in disorder-generated
multifractal patterns we investigate analytically as well as numerically the
statistics of high values of the simplest model - the ideal periodic
Gaussian noise. By employing the thermodynamic formalism we predict the
characteristic scale and the precise scaling form of the distribution of number
of points above a given level. We demonstrate that the powerlaw forward tail of
the probability density, with exponent controlled by the level, results in an
important difference between the mean and the typical values of the counting
function. This can be further used to determine the typical threshold of
extreme values in the pattern which turns out to be given by
with . Such observation provides a
rather compelling explanation of the mechanism behind universality of .
Revealed mechanisms are conjectured to retain their qualitative validity for a
broad class of disorder-generated multifractal fields. In particular, we
predict that the typical value of the maximum of intensity is to be
given by , where is the
corresponding singularity spectrum vanishing at . For the
noise we also derive exact as well as well-controlled approximate
formulas for the mean and the variance of the counting function without
recourse to the thermodynamic formalism.Comment: 28 pages; 7 figures, published version with a few misprints
corrected, editing done and references adde
Semiclassical Quantization of the Triaxial Rigid Rotator: Density of States and Spectral Statistics
VizieR Online Data Catalog: Multi-resolution images of M33 (Boquien+, 2015)
2015yCat..35780008B - VizieR On-line Data Catalog: J/A+A/578/A8. Originally published in: 2015A&A...578A...8BThe FITS file contains maps of the flux in star formation tracing bands, maps of the SFR, maps of the attenuation in star formation tracing bands, and a map of the stellar mass of M33, each from a resolution of 8"/pixel to 512"/pixel.The FUV GALEX data from NGS were obtained directly from the GALEX website through GALEXVIEW. The observation was carried out on 25 November 2003 for a total exposure time of 3334s.Hα+[NII] observations were carried out in November 1995 on the Burrel Schmidt telescope at Kitt Peak National Observatory. The observations and the data processing are analysed in detail in Hoopes & Walterbos (2000ApJ...541..597H).The Spitzer IRAC 8um image sensitive to the emission of Polycyclic Aromatic Hydrocarbons (PAH) and the MIPS 24um image sensitive to the emission of Very Small Grains (VSG) were obtained from the NASA Extragalactic Database and have been analysed by Hinz et al. (2004ApJS..154..259H) and Verley et al. (2007A&A...476.1161V, Cat. J/A+A/476/1161).The PACS data at 70um and 100um, which are sensitive to the warm dust heated by massive stars, come from two different programmes. The 100um image was obtained in the context of the Herschel HerM33es open time key project (Kramer et al., 2010A&A...518L..67K, observation ID 1342189079 and 1342189080). The observation was carried out in parallel mode on 7 January 2010 for a duration of 6.3h. It consisted in 2 orthogonal scans at a speed of 20"/s, with a leg length of 7'. The 70um image was obtained as a follow-up open time cycle 2 programme (OT2mboquien4, observation ID 1342247408 and 1342247409). M33 was scanned on 25 June 2012 at a speed of 20"/s in 2 orthogonal directions over 50' with 5 repetitions of this scheme in order to match the depth of the 100um image. The total duration of the observation was 9.9h.The cube, cube.fits files, contains 16 extensions: * FUV * HALPHA * 8 * 24 * 70 * 100 * SFR_FUV * SFR_HALPHA * SFR_24 * SFR_70 * SFR_100 * SFRFUV24 * SFRHALPHA24 * A_FUV * A_HALPHA * MSTAREach extension od FITS file content 505 "versions". For each extension , the FITS header indicates the positions (RA/DEC) (via the keywords CRVAL/CTYPE/CRPIX/CD), the number of pixels (via the keyword NAXIS), as well as the units (UNIT) and the resolution in human reading format (RESOL). The number of pixels, the sizes, and the coordinates change for one "version" to an other. But these quantities are identical for the different extensions which have the same version name.The two primary keys are the extension name and the version number.The version number indicates the resolution: version+8=resolution in arcsec/pixel
Common Elements Regulating Gene Expression in Temperate and Lytic Bacteriophages of Lactococcus
Ocean Decade Vision 2030 White Papers – Challenge 2: Protect and Restore Ecosystems and Biodiversity.
This draft White Paper has been prepared as part of the Vision 2030 process being undertaken in the framework of the UN Decade of Ocean Science for Sustainable Development. The Vision 2030 process aims to achieve a common and tangible measure of success for each of the ten Ocean Decade Challenges by 2030. From a starting point of existing initiatives underway in the Ocean Decade and beyond, and through a lens of priority user needs, the process determines priority datasets, critical gaps in science and knowledge, and needs in capacity development, infrastructure and technology required for each Challenge to ensure that it can be fulfilled by the end of the Ocean Decade in 2030. The results of the process will contribute to the scoping of future Decade Actions, identification of resource mobilization priorities, and ensuring the ongoing relevance of the Challenges over time. The process identifies achievable recommendations that can be implemented in the context of the Decade, or more broadly before 2030 to achieve the identified strategic ambition and indicators that will be used to measure progress. This draft White Paper is one of a series of ten White Papers all of which have been authored by an expert Working Group. Accompanied by a synthesis report authored by the Decade Coordination Unit, this white paper was discussed at the 2024 Ocean Decade Conference (Barcelona. Spain). Input received from diverse groups through public consultation and at the Conference was reviewed and incorporated as relevant
A transition in the spectral statistics of quantum optical model by different electromagnetic fields
In this paper, we have considered the effects of different quantized electromagnetic fields on the spectral statistics of two-level atoms. The Berry-Robnik distribution and the maximum likelihood estimation technique are used to analyze the effect of the mean photon numbers, the two level atoms numbers and also the quantum number of considered states on the fluctuation properties of different systems which are described by different sets of the Dicke Hamiltonian’s parameters. Our results describe the obvious effect of mean photon number on the spectral statistics and show more regular dynamics when this quantity reaches 700. Also, we observed universality in the spectral statistics of considered systems when the number of two level atoms approaches an unrealistic limit (NA ~ 200) and there are some suggestions about the effect of the quantum number of selected levels and the atom-field coupling constant on level statistics