Assigned ID: 585 ----- Attempting Submission 1 (Fri Feb 25 20:06:21 GMT 2011) ----- HST Phase I Proposal 585 (perseus.apt) successfully submitted. ----- Attempting Submission 2 (Fri Feb 25 20:41:40 GMT 2011) ----- ACQ/SEARCH not specified because target NGC1275 nucleus position is known to milliarcsec precision in ICRS. This is a resubmission, changing the central wavelength setting to 1105 for visit 01. And again resubmitted. New ETC ID numbers for the new wavelength setting and adding in the Ly-Alpha line. ----- Attempting Submission 1 (Thu Jun 30 13:23:03 GMT 2011) ----- ----- Attempting Submission 2 (Mon Mar 05 13:10:28 GMT 2012) ----- ----- Attempting Submission 3 (Thu Mar 22 12:59:46 GMT 2012) ----- ACQ/SEARCH not specified because target NGC1275 nucleus position is known to milliarcsec precision in ICRS. Halpha filaments are common in and around the brightest central galaxy in cool-core clusters of galaxies. A spectacular example occurs around NGC1275 in the nearby Perseus cluster. The low ionization spectrum of the filaments does not match that of any Galactic nebula and is not explained by any plausible photoionizing source. We have shown that the spectrum can be accounted for by ionization and excitation by ionizing particles, produced as the surrounding hot gas particles interpenetrate the cold atomic and molecular filament gas. Strong CI 1656A emission is predicted, as is HeII 1640A and a distinctive continuum. These, and other lines in the UV are sensitive to the energy injection mechanism. We propose to obtain a FUV spectrum of the outer horseshoe filament in the Perseus Cluster, using COS, to detect and measure these lines and the continuum to determine how these filaments are powered. We propose to obtain a deep COS FUV spectrum of the well-studied bright knot at the base of the horseshoe filament (red circle, Fig.~2). We have much supporting data for this region. The G140L grating will allow us to cover the wavelength region from 1120-2246\AA. This broad coverage is crucial since it contains the Ly$\alpha$ He\,II 1640\AA\ and C\,I 1656\AA, lines which our models predict will be present, as well as the distinctive 2-photon continuum. We expect many other lines such as C\,II 1335\AA, C\,III 1909\AA, C\,IV 1150\AA, Si\,II 1335\AA, Si\,IV 1498\AA, N\,V 1240\AA, O\,I 1308\AA\ to be absent. It is important to check that they are not seen as they could be formed by other heating mechanisms such as shocks or photoionization. Our particle heating model predicts that Ly$\alpha$ will be the strongest line in our waveband. However the flux from Ly$\alpha$ is difficult to predict robustly because of the sensitivity of resonant scattering to the turbulent velocity field. Resonant scattering of Ly$\alpha$ in a dusty line forming region (which our models are) leads to photon destruction on dust grains. We therefore use the predicted strength of the C\,I 1656\AA\ and the continuum to calculate exposure times. Our particle heating model predicts the C\,I line to be approximately 30\% of the brightness of H$\beta$. The work of Conselice et al (2001) (their Table 1, region number 11) indicates that the horseshoe knot has a (extinction corrected) surface brightness of $7.2\times10^{-15}$\ergpspscmpsas in H$\alpha$+[N\,II] in an aperture of 1 arcsec radius. We scale this flux by a factor of 0.5 to obtain the H$\alpha$ surface brightness, a factor of 0.27 (Ferland et al 2009, Appendix A) to obtain the H$\beta$ surface brightness, a factor of 0.3 to obtain the CI surface brightness and a factor of 0.28 to account for reddening assuming E(B-V)=0.17 (Conselice et al 2001 and Fig 11.3 of the COS Instrument Handbook for Cycle 19). This yields a predicted surface brightness of $8.3\times10^{-17}$\ergpspscmpsas. The predicted continuum surface brightness is $4.2\times10^{-18}$\ergpspscmpapsas. Setting these surface brightness into the COS ETC with a source diameter of 2 arcsec gives the following counts at 1685\AA\ (the redshifted wavelength of the C\,I line) in a 20000~sec observation, per cross-dispersion resolution element of 47 pixels, per 0.08\AA\ pixel in the wavelength direction; Line: 1.56 cts, Continuum: 0.61 cts, Dark: 2.15 cts. In the line we get a signal-to-noise ratio (SNR) of 0.75 per wavelength bin. Since our target essentially fills the COS aperture the C\,I line is spread out over 100 wavelength bins which combine to increase the SNR to 7.5, allowing a flux measurement to 13\% accuracy. If the He\,II line is as strong as in the HUT spectrum we would expect to detect this with a SNR of about 5. Binning up over 50\AA\ allows us to detect the continuum at an SNR of 10 at the wavelength if C\,I. More counts will be detected at shorter wavelengths allowing a finer grained definition of the continuum near the short wavelength turnover. This 20000 sec exposure can be obtained in 7 orbits of telscope time assuming 56 minutes of visibility per orbit and the standard guide star and target acquisitions and published detector overheads. ISM IN EXTERNAL GALAXIES 12 false 0.0 0.0 false false false false SUPPORTED GALAXY BCM ELLIPTICAL Position is from VLBI from Ma et al 1998, AJ 116, 516 Flux at 1600 (FOS 0.21x1.23 aperture) from Johnstone + Fabian 1995 MNRAS 273, 625. Flux at 2300A confirmed from small extrapolation of preview data for HST dataset O62O05010 (2000-08-18) STIS 52x0.2. That spectrum is largely in agreement with F320W columns in Table 5 of Zirbel + Baum 1998, ApJ, 114, 177 when only point source component is taken into account. J2000 1+/-0.2 e-15 erg/cm/cm/s/A at 1600A, 3.2e-15 erg/cm/cm/s/A at 2300A EXT-MEDIUM COOLING FLOW EMISSION LINE NEBULA FILAMENT COS/FUV Spectroscopic No No G140L 1105 1330617218233 The scheduling data was generated by CASM 20.0. CASM was run in Phase II mode. 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