An Imaging Survey of Northern Galactic H<i>α</i> Emission with Arcminute Resolution

Dennison, B.; Simonetti, J. H.; Topasna, Gregory A.

doi:10.1071/as98147

Cited by 116 publications

(99 citation statements)

References 6 publications

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“…Free-free emission arises from electron-ion scattering which produces microwaves with a brightness spectrum T A $ (EM/1 cm À6 pc) À2:14 for frequencies > 10 GHz, where EM is the emission measure, R n 2 e dl, and we assume an electron gas temperature T e $ 8000 K. As discussed in Bennett et al (2003c), high-resolution maps of H emission (Dennison et al 1998;Haffner et al 2003;Reynolds et al 2002;Gaustad et al 2001) can serve as approximate tracers of free-free emission. The intensity of H emission is given by …”

Section: Free-free Emissionmentioning

confidence: 99%

Three‐YearWilkinson Microwave Anisotropy Probe(WMAP) Observations: Temperature Analysis

Hinshaw

Nolta

Bennett

et al. 2007

ASTROPHYS J SUPPL S

1,180

1,209

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We present new full-sky temperature maps in five frequency bands from 23 to 94 GHz, based on data from the first 3 years of the WMAP sky survey. The new maps are consistent with the first-year maps and are more sensitive. The 3 year maps incorporate several improvements in data processing made possible by the additional years of data and by a more complete analysis of the polarization signal. These include several new consistency tests as well as refinements in the gain calibration and beam response models. We employ two forms of multifrequency analysis to separate astrophysical foreground signals from the CMB, each of which improves on our first-year analyses. First, we form an improved ''Internal Linear Combination'' (ILC) map, based solely on WMAP data, by adding a bias-correction step and by quantifying residual uncertainties in the resulting map. Second, we fit and subtract new spatial templates that trace Galactic emission; in particular, we now use low-frequency WMAP data to trace synchrotron emission instead of the 408 MHz sky survey. The WMAP point source catalog is updated to include 115 new sources whose detection is made possible by the improved sky map sensitivity. We derive the angular power spectrum of the temperature anisotropy using a hybrid approach that combines a maximum likelihood estimate at low l (large angular scales) with a quadratic cross-power estimate for l > 30. The resulting multifrequency spectra are analyzed for residual point source contamination. At 94 GHz the unmasked sources contribute 128 AE 27 K 2 to l(l þ 1)C l /2 at l ¼ 1000. After subtracting this contribution, our best estimate of the CMB power spectrum is derived by averaging cross-power spectra from 153 statistically independent channel pairs. The combined spectrum is cosmic variance limited to l ¼ 400, and the signal-to-noise ratio per l-mode exceeds unity up to l ¼ 850. For bins of width Ál/l ¼ 3%, the signal-to-noise ratio exceeds unity up to l ¼ 1000. The first two acoustic peaks are seen at l ¼ 220:8 AE 0:7 and l ¼ 530:9 AE 3:8, respectively, while the first two troughs are seen at l ¼ 412:4 AE 1:9 and l ¼ 675:2 AE 11:1. The rise to the third peak is unambiguous; when the WMAP data are combined with higher resolution CMB measurements, the existence of a third acoustic peak is well established. Spergel et al. use the 3 year temperature and polarization data to constrain cosmological model parameters. A simple six-parameter ÃCDM model continues to fit CMB data and other measures of large-scale structure remarkably well. The new polarization data produce a better measurement of the optical depth to reionization, ¼ 0:089 AE 0:03. This new and tighter constraint on helps break a degeneracy with the scalar spectral index, which is now found to be n s ¼ 0:960 AE 0:016. If additional cosmological data sets are included in the analysis, the spectral index is found to be n s ¼ 0:947 AE 0:015.

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Section: Free-free Emissionmentioning

confidence: 99%

Three‐YearWilkinson Microwave Anisotropy Probe(WMAP) Observations: Temperature Analysis

Hinshaw

Nolta

Bennett

et al. 2007

ASTROPHYS J SUPPL S

1,180

1,209

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“…We also looked at the relevant field (Mon07) from the Virginia Tech Spectral-Line Survey (VTSS; Dennison, Simonetti, & Topasna 1998). The VTSS resolution is coarser than SHASSA (1.6 pixels) and consequently it is more difficult to adequately subtract the diffuse background.…”

Section: Shassa and Vtss Imagesmentioning

confidence: 99%

PFP 1: A Large Planetary Nebula Caught in the First Stages of ISM Interaction

Pierce

Frew

Parker

et al. 2004

Publ. – Astron. Soc. Aust

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This paper presents (Hα + [Nii]) imaging and spectroscopy of a previously unknown, highly evolved planetary nebula of low excitation which is in the first stages of an interaction with the interstellar medium (ISM). It was discovered serendipitously from AAO/UKST Hα Survey images as part of a project to exploit the survey data and has evaded detection by previous surveys due to its very low surface brightness. It is a remarkable hollow-sphere planetary nebula, some 19 across, making it one of the largest examples of its type. We estimate a radius of 1.5 pc and a distance of 550 pc as derived from a new Hα surface brightnessradius relation. PFP 1 has near-perfect circular symmetry, broken only at the north-western edge which is coupled with significantly increased (Hα + [Nii]) intensity, both of which provide evidence for an interaction with the ISM. We find a near solar composition for this object with possibly enhanced He and N abundances. A blue central star candidate has been identified from the SuperCosmos Sky Survey data.

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“…We have chosen Hα as the most optimum emission-line, firstly as it best represents the nebular ionized mass, and secondly because a number of narrowband Hα imaging surveys have recently become available, from which large numbers of accurate integrated fluxes, diameters, and surface brightnesses can be determined. These include the SuperCOSMOS H-alpha Survey (SHS; Parker et al 2005;Frew et al 2014a), the INT Photometric HAlpha Survey (IPHAS; Drew et al 2005), the VST Photometric H-Alpha Survey (VPHAS+; Drew et al 2014), and the lowerresolution Southern H-Alpha Sky Survey Atlas (SHASSA; Gaustad et al 2001) and Virginia-Tech Sky Survey (VTSS; Dennison, Simonetti & Topasna 1998).…”

Section: Introductionmentioning

confidence: 99%

The H surface brightness-radius relation: a robust statistical distance indicator for planetary nebulae

Frew¹,

Parker²,

Bojičić³

2015

Monthly Notices of the Royal Astronomical Society

173

127

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Measuring the distances to Galactic planetary nebulae (PNe) has been an intractable problem for many decades. We have now established a robust optical statistical distance indicator, the Hα surface brightness -radius or S Hα -r relation, which addresses this problem. We developed this relation from a critically evaluated sample of primary calibrating PNe. The robust nature of the method results from our revised calibrating distances with significantly reduced systematic uncertainties, and the recent availability of high-quality data, including updated nebular diameters and integrated Hα fluxes. The S Hα -r technique is simple in its application, requiring only an angular size, an integrated Hα flux, and the reddening to the PN. From these quantities, an intrinsic radius is calculated, which when combined with the angular size, yields the distance directly. Furthermore, we have found that optically thick PNe tend to populate the upper bound of the trend, while optically-thin PNe fall along the lower boundary in the S Hα -r plane. This enables sub-trends to be developed which offer even better precision in the determination of distances, as good as 18 per cent in the case of optically-thin, high-excitation PNe. This is significantly better than any previous statistical indicator. We use this technique to create a catalogue of statistical distances for over 1100 Galactic PNe, the largest such compilation in the literature to date. Finally, in an appendix, we investigate both a set of transitional PNe and a range of PN mimics in the S Hα -r plane, to demonstrate its use as a diagnostic tool. Interestingly, stellar ejecta around massive stars plot on a tight locus in S Hα -r space with the potential to act as a separate distance indicator for these objects.

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An Imaging Survey of Northern Galactic Hα Emission with Arcminute Resolution

Cited by 116 publications

References 6 publications

Three‐YearWilkinson Microwave Anisotropy Probe(WMAP) Observations: Temperature Analysis

Three‐YearWilkinson Microwave Anisotropy Probe(WMAP) Observations: Temperature Analysis

PFP 1: A Large Planetary Nebula Caught in the First Stages of ISM Interaction

The H surface brightness-radius relation: a robust statistical distance indicator for planetary nebulae

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