Low redshift Lyman-alpha blobs

0 Assigned ID: 648 ----- Attempting Submission 1 (Fri Apr 07 17:06:40 GMT 2017) ----- HST Phase I Proposal 648 (LAB_GO.apt) successfully submitted. Receipt: # 648-1 1st iteration. The orbital setup is the same as for my previous proposal (#14749). The only difference is that here I had to introduce roll angle constraints because of neighboring targets, for which I want to minimize spectral overllap in the slitless mode. This particularly constraints the schedulability of J1455+0446. 481127379 ----- Attempting Submission 1 (Sun Jul 02 16:27:02 GMT 2017) ----- Low redshift Lyman-alpha blobs Lyman-alpha blobs (LABs) are luminous nebula at redshifts of 2 and beyond. Their nature and ionization sources have remained mysterious. The lack of accessible diagnostic emission lines and the poorly understood Lyman-alpha escape mechanism have so far prevented a consistent physical picture of LABs. We suggest that many LABs harbor transient AGN that have recently and quickly faded from our view; the Ly-alpha photons from the earlier quasar phase, however, are resonantly scattered and slowly released over times much longer than the LABs' light crossing time. These ionization echoes naturally explain the severe power deficits observed in LABs. We have identified a rare population of ultra-luminous [OIII] ionization echoes around transient AGN at redshifts z=0.3. They share many characteristics of LABs, including high Lyman-alpha luminosities of up to 7e43 erg/s as suggested by GALEX FUV images. We ask to observe three targets to verify the strong Lyman-alpha emission using ACS/SBC. This would prove that LABs may still exist in the Universe 7 billion years later than most other LABs known. It would also show that fading AGN explain the power deficits of many LABs, solving a puzzle that has been standing for nearly two decades. In combination with our existing ground-based imaging and 3D spectroscopy, and soft-and hard X-ray data, we will exploit the HST far-UV data to also study the Lyman-alpha escape mechanism. This proposal is a continuation of our cycle 24 allocation, to complete the far-UV data for the most luminous LABs in our sample. This proposal exploits the unique far-UV capabilities of HST. This program aims to obtain far-UV spectra and images with ACS/SBC, for a total of three targets. The targets are galaxies at redshift 0.3, embedded in luminous clouds of ionized gas. The clouds have diameters between 10-25 arcseconds, and we want to determine their Lyman-alpha properties. Each target has one visit, consisting of two orbits. In the first orbit, we take a slitless spectrum of the source, followed by an image in the second orbit. The science exposures (spectrum and image) are split into two sub-exposures of approximately equal length (1300s), using a line dither pattern to reject detector defects. The purpose of the spectrum (first orbit) is to determine the total amount of flux in the Lyman-alpha line, and to measure the flux in the continuum (if any). The purpose of the image (second orbit) is to obtain a deeper view to determine morphology and size. Ihe image is also needed to reduce the slitless spectrum. Absolute flux calibration is important. This will mainly be based on the slitless spectrum, where we can isolate the effects of the red leaks. All our targets are covered by GALEX imaging, no FUV-bright stars are in the field of view. Massive Black Holes And Their Host Galaxies 6 false true false false false false SUPPORTED GALAXY EMISSION LINE NEBULA LYMAN ALPHA CLOUD NLR QUASAR YES Source diameter: 5x9 arcsec J1347-5453 J2000 J2000 r=18.7, GALEX FUV=31.0 microjansky integrated over the entire source GALAXY EMISSION LINE NEBULA LYMAN ALPHA CLOUD NLR QUASAR YES Source diameter: 6x9 arcsec J1455+0446 J2000 J2000 r=18.5, GALEX FUV=19.8 microjansky integrated over the entire source GALAXY EMISSION LINE NEBULA LYMAN ALPHA CLOUD NLR QUASAR YES Source diameter: 7x7 arcsec J1505+1944 J2000 J2000 r=17.9, GALEX FUV=22.7 microjansky integrated over the entire source ACS/SBC Spectroscopic No No PR130L ACS/SBC Imaging No No F140LP ACS/SBC Spectroscopic No No PR130L ACS/SBC Imaging No No F140LP ACS/SBC Spectroscopic No No PR130L ACS/SBC Imaging No No F140LP POS-TARG DITHER 0.472 We choose the default line pattern to reject detector blemishes LINE false false 2 44.4 ACS-SBC-DITHER-LINE 1

false

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