Interstellar Movie Download In Hindi 720p Hd Resolutionl
Matty Fiedler
Context.With current wide-field near-infrared (NIR) instruments the scattered lightin the near-infrared can be mapped over large areas. Below mag the surface brightness is directly proportional to the columndensity, and at slightly higher column densities the saturation of theintensity values can be corrected using the ratios of the intensity indifferent NIR bands. Therefore, NIR scattered light provides a promising newmethod for the mapping of quiescent interstellar clouds.
Aims.We develop a method to convert the observed near-infrared surface brightnessinto estimates of the column density. We study and quantify the effectthat different error sources could have on the accuracy of such estimates.We also propose to reduce systematic errors by combining surface brightnessdata with extinction measurements derived from the near-infrared colour excessof background stars.
Methods.Our study is based on a set of three-dimensional magnetohydrodynamicturbulence simulations. Maps of near-infrared scattered light are obtained with radiative transfer calculations, and the maps are converted back into column density estimates using the proposed method. The results are compared with the true column densities. Extinction measurements are simulated using the same turbulence simulations, and are used as a complementary column density tracer.
Results.We find that NIR intensities can be converted into a reliable estimate of the column density in regions with AV up to almost 20 mag. We show that the errors can be further reduced with detailed radiative transfer modelling and especially by using the lower resolution information available through the colour excess data.
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The interstellar medium of our Galaxy (ISM) is a mixture of dust andgas in the form of atoms, molecules, ions, and electrons. It manifestsitself primarily through obscuration, reddening and polarization ofstarlight and the formation of absorption lines in stellar spectra, andsecondly through various emission mechanisms (broadband continuum andline emission). The gas is found in both neutral and ionized phases(for a review, see Ferrire 2001).The neutral phase is a blend of cold molecular gas( K), found in theso-called dark clouds, and cold atomic gas ( K) inherent in thediffuse clouds, while the warm atomic gas hastemperatures of up to 104 K. The atomicgas is well traced by H I and mainlyconcentrated in the Galactic plane with clouds up to few hundreds pcabove it. The warm ionized gas is a weakly ionizedgas, with a temperature of K.It is mainly traced by H-lineemission and pulsar dispersion measures; it can reach a vertical heightof 1 kpc. The hot ionized gas ischaracterized by temperatures of about 106 K.It is heated by supernovae and stellar winds from massive stars; itgives rise to high-ionization absorption lines and the soft X-raybackground emission. The study of the ISM is very interesting becauseof its connection with the evolution of the entire Galaxy: the stellarevolution enriches the interstellar medium with heavy elements, whilethe ISM acts as a source of matter for the star-forming regions.
High-resolution X-ray spectroscopy has become a powerfuldiagnostic tool for constraining the chemical and physical propertiesof the ISM. Through the study of the X-ray absorption lines in thespectra of background sources it is possible to probe the variousphases of the ISM of the Galaxy. First of all, the K-shell transitionsof low-Z elements, such as oxygen and neon, and the L-shell transitionsof iron fall inside the soft X-ray energy band. Secondly, the differentcharge states for each element allow us to constrain the multiphaseISM, e.g. its ionization state and temperature distribution.
Schattenburg &Canizares (1986) first measured ISM absorption edges in theX-ray band with the Einstein Observatory and foundfeatures consistent with the O I 1s-2p lineand traces of O II. After the launch of theXMM-Newton and Chandrasatellites a new era for the ISM study opened up. The gratingspectrometers onboard these satellites, RGS and LETGS/HETGSrespectively, provide a spectral resolution that is high enough toresolve the main absorption edges and lines. Recently, Yao et al. (2009) foundhigh-ionization absorption lines of ions such as O VIto O VIII and Ne VIIIto Ne X in the HETGS spectrum of thelow-mass X-ray binary Cyg X-2, and argued that the bulk ofthe O VI should originate from theconductive interface between the cool and the hot gas. Otherwork has revealed a complex structure around theoxygen K-shell absorption edge (Paerels et al. 2001; Juettet al. 2004; de Vries et al. 2003). Costantini et al. (2005)argued that the feature of the scattering halo of Cyg X-2 near the O I K-edgecan be attributed to dust towards the source, with a major contributionfrom silicates such as olivine and pyroxene. In their paper on ScoX-1, observed with XMM-Newton, de Vries & Costantini (2009)found clear indications of extended X-ray absorption fine structures(EXAFS) near the absorption edge of oxygen.
In this work we report the detection of absorption lines andedges in the high-quality spectrum of the low-mass X-ray binary (LMXB)GS 1826-238 obtained with the XMM-NewtonReflection Grating Spectrometer (RGS, denHerder et al. 2001). In order to constrain thecontinuum parameters we also used the EPIC-pn (Strderet al. 2001) dataset of this source. Thompson et al. (2008),using the XMM-Newton and RXTE observations of April2003, derived a high unabsorbed bolometric flux.The source is well suited for the analysis of the ISM also because ofits column density(seeTable 3),which is sufficiently high to produce prominent O and Fe edges. Weassume the distance of the source to be kpc(Heger et al. 2007).
We analyze the absorption in the spectrum as follows. We firstremove the bursts, because they add a strongly variable component tothe spectrum. Then we determine the source continuum by simultaneouslyfitting EPIC and RGS data. In a second instance we use only thehigh-resolution RGS spectra to constrain the absorption contributions.We search for statistically significant features by adding severalabsorbers in sequence: cold gas, warm gas, hot gas, dust, andmolecules. All of these appear to be important.
GS 1826-238 is a bursting LMXB with a regular time separationbetween the bursts. Because the primary aim of the XMM-Newtonobservations was the study of the bursts, the EPIC-pn detector wasoperated in timing mode, which means that imaging is made only in onedimension, along the RAWX axis. Along the row direction (RAWY axis),data from a predefined area on one CCD chip are collapsed into aone-dimensional row for a fast read-out. Then source photons areextracted between RAWX values 30-45 and background photons areextracted between rows 2-16, as recommended by the standard procedure.
Mean profile of the bursts in the RGS lightcurve of the firstobservation. The zero point of the timescale is centered on the burstprofile peak. The red line represents the mean count rate of the 2 ksaround the peaks.Open with DEXTERWe produced pn lightcurves mainly to remove the burst intervals and toextract the spectra of the persistent part of the lightcurve. In thefirst observation nine bursts we detected, in the second observationseven bursts. We plot the burst profiles of these 16 bursts inFig. 2.We estimate a mean duration of about 300 s for the bursts, and weremoved for each burst 50 s before the peak to 250 s after it. Recentlyin't Zand et al. (2009)suggested a mean duration of about 1 ks for the bursts, but they alsoargued that after the first 100 s the inferred emission decreasessharply by at least one order of magnitude, contributing only about 3%to the fluence in the burst. After 250 s the flux of the burst hasdecreased by almost two orders of magnitude and its profile merges withthe persistent lightcurve. Thus, by removing 300 s for each burst, weretain less than 1%burst emission, which is negligible compared to the persistentemission.
We processed the RGS data with the SAS task rgsproc.We produced the lightcurves for the background in CCD9 following theXMM-SAS guide in order to remove softproton flares and spurious events. We created good time intervals (GTI)by removing intervals with count rates higher than 0.5 c s-1.We reprocessed the data again with rgsproc byfiltering them with the GTI for background screening and burstsremoval. We extracted response matrices and spectra for the twoobservations. The final net exposure times are reported inTable 1.
The first step of the spectral analysis consists of the determinationof the continuum emission and the dominant absorption component. Thebest way to do this is to fit the spectra of RGS and EPIC-pnsimultaneously. The XMM-Newton cross-calibration isvery complex, not only because of the different energy bands, butmainly because of their different features: RGS is sensitive in thesoft X-ray energies with high spectral resolution, showing narrowabsorption features, while pn has a low spectral resolution, thereforeblurring the absorption features seen with RGS. EPIC-pn has a highercount rate compared to RGS and a broader energy band. The original RGSspectra are binned by a factor of 10 in this simultaneous fit. This isnecessary to temporarily remove the narrow features due to theabsorption lines. The pn spectra are resampled in bins of about 1/3 ofthe spectral resolution (FWHM 50-150 eV between 0.5-10 keV), which is the optimal binning for mostspectra.
A better local fit for absorption edges and lines is obtainedfrom a separate RGS fit. In the RGS local fit we rebin the spectra onlyby a factor of two, i.e. about 1/3 FWHM (the firstorder RGS spectra provide a resolution of 0.06-0.07 ). Thisgives at least 10 counts/bin and a bin size of about 0.02 .
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