Redshift Drift using Strong Lenses - 9 views

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  #1 Eric Linder on 28 Feb 14

   

  In http://arxiv.org/abs/1402.6614 we talk briefly about using strong lensing time delays to map the redshift drift over a time lag given by the images' time delays. There are quite a few things still to work out on this, such as finding ultra long delay systems and ensuring systematics don't swamp the signal. Anyone interested in collaborating on this?

   

  <div class="cArrow"> </div><div class="cContentInner">In <a href="http://arxiv.org/abs/1402.6614" rel="nofollow" target="_blank">http://arxiv.org/abs/1402.6614</a> we talk briefly about using strong lensing time delays to map the redshift drift over a time lag given by the images' time delays. There are quite a few things still to work out on this, such as finding ultra long delay systems and ensuring systematics don't swamp the signal. Anyone interested in collaborating on this?</div>

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  #2 Thomas Collett on 02 Mar 14

   

  It's a really interesting paper, but I had two questions about the strong lensing part:
  1) Is it remotely plausible without time delays ~100 years?
  2) I was confused when you mentioned the lyman alpha forest adding to the signal - does it matter that the multiple images have travelled through slightly different regions? What if the lyman alpha absorbers are rotating?

   

  <div class="cArrow"> </div><div class="cContentInner">It's a really interesting paper, but I had two questions about the strong lensing part: <br /> 1) Is it remotely plausible without time delays ~100 years? <br /> 2) I was confused when you mentioned the lyman alpha forest adding to the signal - does it matter that the multiple images have travelled through slightly different regions? What if the lyman alpha absorbers are rotating?</div>

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  #3 Eric Linder on 21 Apr 14

   

  If the measurement precision is good enough, then time delays of a few years might be interesting, especially because the drift measurement is differential between the images, rather than absolute. But no guarantees without more work!
  For LyA I'm trying to think clearly about how we translate the measured quasar time delays into the LyA time delays (since they are at different redshifts, and hence positions along the photon paths) - I think it's straightforward if you know the cosmology but it's not clear if there's a good iterative approach.

   

  <div class="cArrow"> </div><div class="cContentInner">If the measurement precision is good enough, then time delays of a few years might be interesting, especially because the drift measurement is differential between the images, rather than absolute. But no guarantees without more work! <br /> For LyA I'm trying to think clearly about how we translate the measured quasar time delays into the LyA time delays (since they are at different redshifts, and hence positions along the photon paths) - I think it's straightforward if you know the cosmology but it's not clear if there's a good iterative approach.</div>

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  #4 Thomas Collett on 21 Apr 14

   

  Thanks Eric. How bright do you think the lensed quasars need to be? How does the trade off between flux and timedelay work out? I looked into redshift drift a few years ago, and based on the assumptions of Liske 2008's paper it seemed that you needed ultra-bright QSOs to make the experiment work.
  
  I guess my long winded question is; do you have an idea of how many suitable lensed targets there are per sky? And if source flux is important, should we have already found all the suitable candidates in the SDSS footprint?

   

  <div class="cArrow"> </div><div class="cContentInner">Thanks Eric. How bright do you think the lensed quasars need to be? How does the trade off between flux and timedelay work out? I looked into redshift drift a few years ago, and based on the assumptions of Liske 2008's paper it seemed that you needed ultra-bright QSOs to make the experiment work. <br /> <br /> I guess my long winded question is; do you have an idea of how many suitable lensed targets there are per sky? And if source flux is important, should we have already found all the suitable candidates in the SDSS footprint?</div>

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