0 Assigned ID: 384 ----- Attempting Submission 1 (Fri Apr 05 09:36:31 GMT 2019) ----- Changed to TIME-TAG mode for the MAMA observations -1997854903 ----- Attempting Submission 1 (Wed Jul 24 16:15:41 GMT 2019) ----- ----- Attempting Submission 2 (Thu Oct 03 21:22:12 GMT 2019) ----- NGC 3147 has been considered the best case of a true type 2 AGN: an unobscured AGN, based on the unabsorbed compact X-ray continuum, which lacks a broad line region (BLR). However, the very low luminosity of NGC 3147 implies a compact BLR, which produces very broad lines, hard to detect against the background host galaxy. Narrow (0.1"x0.1") slit HST spectroscopy allowed excluding the host galaxy light, and revealed a remarkably strong and extremely broad Halpha line. The line profile shows a very steep blue wing and an extended red wing, the signature of a mildly relativistic thin accretion disk line profile. The line profile is well fit with a nearly face on thin disk (i=23 degrees), with an inner radius at 77 gravitational radii, as expected from the R-L^1/2 relation. This result critically questions the very existence of true type 2 AGN, and is likely to change our current view of the accretion flow at low accretion rates. Here we propose to get the first C IV emission line profile of NGC 3147. Reverberation mapping campaigns indicate that the C IV line is produced in a region which is about half the size of the Balmer line emitting region. This means that the C IV line in NGC 3147 can potentially probe the accretion disk well below 50 gravitational radii, a region currently probed only with X-ray line spectroscopy. Optical detections of relativistic line profiles may provide a new and powerful tool for precision measurements of the innermost accretion disk structure and the BH properties, as the optical photons detection rate is >10^5 higher than in the X-rays. We observe the target using STIS/CCD for 4 orbits with the G750L and the G750M gratings, and the FUV/MAMA with G140L. The observations are aimed at characterizing the expected very broad profile of the C iv line, and getting a higher spectral resolution view of the Halpha emission disk line profile previously detected by STIS G750L. In ground based spectra, the emission of these lines is heavily contaminated by the host galaxy stellar emission. We will use the 52x0.1" slit in order to reduce such a contamination by a factor of ~10 with respect to ground based observations. This choice proved extremely effective with the past STIS G750L observation (GO 15225), which revealed for the first time an extremely broad Halpha in this source. The pointing strategy is the same as in our previous program 15225. We will aim at the host galaxy photocenter. A target acquisition image will be taken to allow recentering on the brightest region, which we know coincides with the AGN, as shown by the previous STIS G750L observation. As recommended in the STIS handbook, we will use the F28X50LP lter for the acquisition image and an exposure time of 60s, as in our previous program that observed the very same target. We performed accurate S/N simulations using the STIS ETC: G750M: the most efficient choice is to use the 6295-6867A band, which covers most of the observed disk line Halpha profile and all the bright NLR lines. Using the observed average flux density of the broad Halpha (0.2x10^-15 erg cm^2 s^-1 A^-1, the ETC returns a S/N ~12 per resolution element in 2000 s, which will be accommodated in the first orbit, after the acquisition image. G750L: a very short repetition of the low resolution Halpha profile is important, since the restricted band of G750M does not allow for a proper determination of the continuum level. It will also be used for a direct comparison of the disk line profile measured in the earlier observation. An exposure of 800s will be accommodated at the beginning of orbit 2. G140L: the C iv line is expected to have about the same flux of the Halpha line, as derived from the SDSS QSO template (Vanden Berk et al., 2001), while the continuum is higher by a factor of 5. The E(B-V) of NGC 3147 is fairly low, being 0.02 mag. Adopting a flux density of 5 x0.15 x10^-15 erg cm^-2 s^-1 A^-1 (5 times the observed continuum level around Halpha), the ETC returns a S/N of 12 per resolution element on the continuum, for an exposure time of 8500 s. The required exposure will be split in three orbits (2100s in orbit 2, and 3200 s in orbit 3 and 4). We use the 52x01E1 aperture to mitigate CTE losses, as suggested by the IHB. For the MAMA observations, we will use the D1 aperture, as recommended in the IHB. We use two CR-SPLIT images at each slit position to eliminate cosmic rays in the CCD exposures. We also include simultaneous flat fields to perform de-fringing at long wavelengths, as recommended by the IHB in Sect. 7.2.6. These flats are taken during occultation, immediately after the last on-target exposure in orbits 1 and 2. Prof. Robert Antonucci has studied many aspects of AGN observationally over the decades, including many HST programs, and ground based and space-based projects at all wavelengths. He's known best for polarization observations leading to the Unified Model of the AGN spectroscopic classes. Prof. Stefano Bianchi is an expert in the field of High Energy Astrophysics of compact objects. Dr. Marco Chiaberge is the PI or co-I of a large number of HST programs mostly focused on AGN and is the lead of the HST-3C project on radio-loud AGN. He first authored more than 15 refereed papers based on HST data and he is an expert in AGN and their environment. He has been leading for almost a decade the calibration of HST's Advanced Camera for Surveys at STScI. Dr. Alessandro Capetti has a wide experience in the analysis and interpretation of HST data, including several programs using STIS aimed at the study of the nuclear regions of AGN and at measuring black masses in both active and quiescent galaxies. Dr. Ari Laor is an expert on the formation and properties of the broad line region, and relativistic disk line profiles. Massive Black Holes And Their Host Galaxies 6 false false false false false false false SUPPORTED GALAXY SEYFERT This object was generated by the targetselector and retrieved from the NED database. The magnitude is the magnitude of the entire galaxy, not the nucleus. Expected nuclear fluxes are given in the Phase I proposal and in the description of the Observations J2000 J2000 STIS/CCD Spectroscopic No No G750M 6581 STIS/CCD Spectroscopic No No G750L 7751 STIS/FUV-MAMA Spectroscopic No No G140L 1425 1570131768928 /private/var/folders/l_/5v2qhxc17r9gmt251m6xf_r80003jg/T/OPVisit11079306423597670386.xml The scheduling data was generated by CASM 27.2. CASM was run in Phase II mode. 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