The Bell Laboratories H I survey

Stark, A. A.; Gammie, Charles F.; Wilson, R. W.; Bally, John; Linke, R. A.; Heiles, Carl; Hurwitz, M.

doi:10.1086/191645

Cited by 896 publications

(918 citation statements)

References 5 publications

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“…The Galactic northsouth asymmetry is more likely to be due to clustering than due to Galactic extinction. This is supported by the Galactic HI map of Stark et al (1992) shown here in Fig. 3, indicating north-south symmetry about the Galactic Plane.…”

Section: Scanning Proceduressupporting

confidence: 75%

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Visual search for galaxies near the northern crossing of the Supergalactic Plane by the Milky Way

Hau¹,

Ferguson²,

Lahav³

et al. 1995

Monthly Notices of the Royal Astronomical Society

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We have visually examined twelve Palomar red Plates for galaxies at low Galactic latitude b, where the Supergalactic Plane (SGP) is crossed by the Galactic Plane (GP), at Galactic longitude l 135 . The catalogue consists of 2575 galaxy candidates, of which 462 have major axis diameters d 0:8 0 (uncorrected for extinction). Galaxy candidates can be identi ed down to jbj 0 . One of our galaxy candidates (J24 = Dwingeloo 1) has recently been discovered independently in 21cm by as a nearby galaxy. Comparisons with the structures seen in the IRAS and UGC catalogues are made. We compare the success rate of identifying galaxies using the IRAS Point Source Catalogue under di erent colour selection criteria. The criteria that require both the 60 m and 100 m uxes to be of high quality, have the highest probability of selecting a galaxy (with d 0:6 0 ), but at the expense of selecting a smaller number of galaxies in total.

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Section: Scanning Proceduressupporting

confidence: 75%

“…In Fig. 3 the contours of Galactic HI from Stark et al (1992) although this relation may not hold tightly in the galactic plane. Galaxies can be seen down to b = 0 , but there is a rapid drop in detection rate for 6 < b < 8 .…”

Section: Scanning Proceduresmentioning

confidence: 96%

Visual search for galaxies near the northern crossing of the Supergalactic Plane by the Milky Way

Hau¹,

Ferguson²,

Lahav³

et al. 1995

Monthly Notices of the Royal Astronomical Society

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“…3.2 with free normalisation for APEC and power-law components and fitted it to the spectrum extracted in the same annulus. We fixed the absorption column density to the Galactic value, that is corresponding to the CDFS direction, N H = 8.8 × 10 19 cm −3 (see Stark et al 1992). This allowed us to completely characterise the spatial variation of the total background (particle plus sky components) over the whole FOV.…”

Section: Analysis Of the Chandra Deep Field Southmentioning

confidence: 99%

ChandraACIS-I particle background: an analytical model

Bartalucci

Mazzotta

Bourdin

et al. 2014

A&A

101

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Aims. Imaging and spectroscopy of X-ray extended sources require a proper characterisation of a spatially unresolved background signal. This background includes sky and instrumental components, each of which are characterised by its proper spatial and spectral behaviour. While the X-ray sky background has been extensively studied in previous work, here we analyse and model the instrumental background of the ACIS-I detector on board the Chandra X-ray observatory in very faint mode. Methods. Caused by interaction of highly energetic particles with the detector, the ACIS-I instrumental background is spectrally characterised by the superimposition of several fluorescence emission lines onto a continuum. To isolate its flux from any sky component, we fitted an analytical model of the continuum to observations performed in very faint mode with the detector in the stowed position shielded from the sky, and gathered over the eight-year period starting in 2001. The remaining emission lines were fitted to blank-sky observations of the same period. We found 11 emission lines. Analysing the spatial variation of the amplitude, energy and width of these lines has further allowed us to infer that three lines of these are presumably due to an energy correction artefact produced in the frame store. Results. We provide an analytical model that predicts the instrumental background with a precision of 2% in the continuum and 5% in the lines. We use this model to measure the flux of the unresolved cosmic X-ray background in the Chandra deep field south. We obtain a flux of 10.

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“…PCA response matrices were calculated individually for each observation using PCARSP V2.37, taking into account temporal variations of the detector gain and the changing number of detectors used. Fluxes in the 2-10 keV band were then determined using XSPEC, fitting a simple powerlaw with variable slope but with absorption fixed at the Galactic level of 1.3×10 20 cm −2 (Elvis, Lockman and Wilkes 1988;Stark et al 1992;M c Hardy et al 1995). The errors in the flux are scaled directly from the observed errors in the measured count rate.…”

Section: Rxtementioning

confidence: 99%

Combined long and short timescale X-ray variability of NGC 4051 with RXTE and XMM-Newton

McHardy¹,

Papadakis²,

Uttley³

et al. 2004

Nuclear Physics B - Proceedings Supplements

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We present a comprehensive examination of the X-ray variability of the narrow line Seyfert 1 (NLS1) galaxy NGC 4051, one of the most variable AGN in the sky. We combine over 6.5 years of frequent monitoring observations by RXTE with a > 100 ks continuous observation by XMM-Newton and so present an overall 2-10 keV powerspectral density (PSD) covering an unprecedent frequency range of over 6.5 decades from < 10 −8 to > 10 −2 Hz. The combined RXTE and XMM-Newton PSD is a very good match to the PSD of the galactic black hole binary system (GBH) Cyg X-1 when in a 'high', rather than 'low', state providing the first definite confirmation of an AGN in a 'high' state. We also find that a bending powerlaw, rather than a sharply broken powerlaw, besides being more physical, is a much better description of the high state PSD of Cyg X-1 and is also a better description of the PSD of NGC 4051.At low frequencies the PSD of NGC 4051 has a slope of -1.1 bending, at a frequency ν B = 8 +4 −3 × 10 −4 Hz, to a slope of α H ∼ −2. Although ν B does not depend on photon energy, α H is steeper at lower energies. If ν B scales with mass, we imply a black hole mass of 3 +2 −1 × 10 5 M ⊙ in NGC 4051, which is consistent with the recently reported reverberation value of 5 +6 −3 × 10 5 M ⊙ . Hence NGC 4051 is emitting at ∼ 30% L Edd . NGC 4051 follows the same rms-flux relationship as GBHs, consistent with higher Fourier frequencies being associated with smaller radii.From the cross-powerspectra and cross-correlation functions between XMMNewton lightcurves in different energy bands, we note that the higher energy photons lag the lower energy ones. We also note that the lag is greater for variations of longer Fourier period and increases with the energy separation of the bands. Variations in different wavebands are very coherent at long Fourier periods but the coherence decreases at shorter periods and as the energy separation between bands increases. This behaviour is again similar to that of GBHs, and of MCG-6-30-15, and suggests a radial distribution of frequencies and photon energies with higher energies and higher frequencies being associated with smaller radii.Combining our observations with observations from the literature we find it is not possible to fit all AGN to the same linear scaling of break timescale with black hole mass. However broad line AGN are consistent with a linear scaling of break timescale with mass from Cyg X-1 in its low state and NLS1 galaxies scale better with Cyg X-1 in its high state. We suggest that the relationship between black hole mass and break timescale is a function of at least one other underlying parameter which may be accretion rate or black hole spin or both.

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The Bell Laboratories H I survey

Cited by 896 publications

References 5 publications

Visual search for galaxies near the northern crossing of the Supergalactic Plane by the Milky Way

Visual search for galaxies near the northern crossing of the Supergalactic Plane by the Milky Way

ChandraACIS-I particle background: an analytical model

Combined long and short timescale X-ray variability of NGC 4051 with RXTE and XMM-Newton

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