Rubin2020_PCW slack archives day2-tue-slot2c-rrb-dm-and-lsb 2020-07-31---2020-08-11

Fri 2020-07-31 08:12PM

@Melissa Graham has joined the channel

Melissa Graham Fri 2020-07-31 08:12PM

@Melissa Graham set the channel purpose: Rubin Research Bytes Session C. Dark Matter and Low Surface Brightness

Melissa Graham Fri 2020-07-31 08:36PM

@Melissa Graham has renamed the channel from "day2-slot-2c-rrb-dm-and-lsb" to "day2-tue-slot-2c-rrb-dm-and-lsb"

Melissa Graham Fri 2020-07-31 08:38PM

@Melissa Graham has renamed the channel from "day2-tue-slot-2c-rrb-dm-and-lsb" to "day2-tue-slot2c-rrb-dm-and-lsb"

Melissa Graham Sat 2020-08-01 01:15PM

@Melissa Graham set the channel topic: Rubin Research Bytes Session C. Dark Matter and Low Surface Brightness
RRB Webpage: <https://project.lsst.org/meetings/rubin2020/agenda/session/rubin-research-bytes>

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Keith Bechtol Tue 2020-08-11 12:56PM

We have a great set of talks coming up in ~30 minutes:
Using the Rubin LSST Science Pipelines to process deep DECam exposures from the LoVoCCS Survey, Shenming Fu Distant Milky Way satellites, Matias Blana The origin of low-surface-brightness galaxies in the dwarf regime, Ryan Jackson Stacking the low surface brightness light envelopes of galaxies and intra-cluster light in DES data, Yuanyuan Zhang
Speakers: @Shenming Fu @Matías Blaña @Ryan Jackson @Yuanyuan Zhang
Moderators: @Lee Kelvin and Keith Bechtol

Tue 2020-08-11 12:56PM

@Yuanyuan Zhang has joined the channel

Keith Bechtol Tue 2020-08-11 01:32PM

Feel free to post questions as you think of them in the Slack channel (preferred) or Zoom chat

Jeff Carlin Tue 2020-08-11 01:36PM

Q for Shenming: Do you adopt any specialized treatment for the background in LoVoCCS processing, or simply use the LSST Stack "defaults"?

Jeff Carlin Tue 2020-08-11 01:42PM: Thanks for the answer, Shenming! I imagine these deep cluster data could be useful for folks in the Galaxies SC who are interested in intracluster light. So even though optimal BG subtraction isn't vital for lensing work, it would enable other science if the BG subtraction was improved.
Shenming Fu Tue 2020-08-11 04:06PM: Yes. We plan to work with the DM team to study how to improve the background subtraction on these DECam images.

Jeff Carlin Tue 2020-08-11 01:37PM

(we can save this :arrow_up: for the Q&A period)

Chuck Claver Tue 2020-08-11 01:38PM

Q: What have you've learned from processing DECam data regarding the effects of image ghosts and scattered light when analyzing data for low surface brightness objects. What should Rubin be looking for during its commissioning phase?

Ian Dellantonio Tue 2020-08-11 01:52PM: Hi Chuck, about 5-10% of chips fail the background variation. Unfortunately, I don't know how many of those are due to scattered light, since some are due to bright satellite trails, too.
Chuck Claver Tue 2020-08-11 01:56PM: :pray:

Chuck Claver Tue 2020-08-11 01:41PM

Q: Follow up - what fraction of data did you have to reject from DECcam?

Chuck Claver Tue 2020-08-11 01:42PM

Thanks!

Melissa Graham Tue 2020-08-11 01:49PM

@here new transition time 11:15am due to technical difficulties

Keith Bechtol Tue 2020-08-11 01:50PM

Thanks a lot for everyone's understanding with the technical issue that prevented some people from joining at the start of the session

Morgan Schmitz Tue 2020-08-11 01:50PM

Thanks for a two great talks Shenming!

Shenming Fu Tue 2020-08-11 01:53PM: Thank you!

Jeff Carlin Tue 2020-08-11 01:55PM

Cool stuff, Matias!

Matías Blaña Tue 2020-08-11 04:51PM: Thank you!

Jeff Carlin Tue 2020-08-11 01:58PM

Q for Ryan: Do you have thoughts about the origin the extremely faint (and low mass) systems below the main locus in your 2nd slide?

Jeff Carlin Tue 2020-08-11 01:58PM

Also - great talk, Ryan!

Ryan Jackson Tue 2020-08-11 02:05PM: Thanks!

Chuck Claver Tue 2020-08-11 02:01PM

Q: On what angular scale, as seen on the sky, is the extent of intra-cluster light?

Yuanyuan Zhang Tue 2020-08-11 02:49PM: Hi Chuck, in my work, I looked to 1Mpc, that would correpond to 1~10 arcmins depending on the redshift. At redshift 0.25, it would be ~4 arcmin in cluster radius, about ~ 8 arcmin in cluster diameter.

Jeff Carlin Tue 2020-08-11 02:03PM

:clap:

Sukanya Chakrabarti Tue 2020-08-11 02:06PM

@Yuanyuan Zhang have you looked at the light to mass ratio with your ICL measurements and determination of total mass from ICL?

Knut Olsen Tue 2020-08-11 02:07PM

Q for Yuanyuan Zhang: what does the good correspondence between the ICL and WL measurement say about the origin of the ICL, given that the dynamical timescales must be quite long at those radii?

Jeff Carlin Tue 2020-08-11 02:13PM: Interesting - I think Yuanyuan was saying that the models show the light being more concentrated than observations. Does the fact that the light is more extended than models suggest that most of the merging was earlier or later (on average) than model predictions?
Knut Olsen Tue 2020-08-11 02:14PM: Yeah, good question!
Knut Olsen Tue 2020-08-11 02:15PM: I think if the models show more concentrated light, it might mean that the matter decouples from the DM too early
Knut Olsen Tue 2020-08-11 02:15PM: Maybe related to feedback?
Yuanyuan Zhang Tue 2020-08-11 02:53PM: Hi Jeff, Knut, indeed good question! I also suspect that, as you two mentioned, that stellar stripping or other disruption of galaxies, is decoupling from dark matter at a (slightly at least) timescale than in simulations. wishing to hear if any simulators have more thoughts about it!

C A Collins Tue 2020-08-11 02:10PM

Q for Yuanyuan: can you please comment on whether ICL converges at R200?

Yuanyuan Zhang Tue 2020-08-11 02:17PM: Hi Chris, interesting question, I wonder too! we haven't pushed the measurements deep enough yet with DES data to tell, but I think deeper DES data has a chance to see it, and LSST can definitely tell that!
C A Collins Tue 2020-08-11 02:42PM: Thanks, yes it has to converge at some point of course and maybe depends on data depth as you say. Aaron Watkins will say more about LSST pipeline and ICL on Thursday, I think he shows your plot from 2019. You gave a nice talk !
Yuanyuan Zhang Tue 2020-08-11 02:46PM: Thank you Chris!

Chris Walter Tue 2020-08-11 02:12PM

For @Shenming Fu (slack only) were the nice galaxy images in your last(?) slide from the output of the Rubin stack?

Jeff Carlin Tue 2020-08-11 02:13PM: Yeah, those were nice images!
Shenming Fu Tue 2020-08-11 02:15PM: Thank you. We took the coadd images from the Rubin stack and then scaled them by ourselves to make these color images (irg bands).

Chuck Claver Tue 2020-08-11 02:15PM

:clap:

Colin Slater Tue 2020-08-11 02:15PM

thanks speakers and organizers too!

Morgan Schmitz Tue 2020-08-11 02:15PM

Yeah, great chairing by Lee and Keith especially considering everything! :slightly_smiling_face:

Yuanyuan Zhang Tue 2020-08-11 02:36PM

I've got a question for Ryan - do you find ultra-diffuse galaxies in your simulation, and are their formation mechanisms different?

Dan Taranu Tue 2020-08-11 02:42PM

Another question for Ryan: Do off-locus galaxies stay off-locus for very long? If the bright ones fade back towards the mean, how long does this take? What about the unusually faint ones?

Lee Kelvin Tue 2020-08-11 02:46PM

@here , thanks again to all our speakers for an excellent session! @Shenming Fu , @Matías Blaña , @Ryan Jackson , @Yuanyuan Zhang :clap:

Chuck Claver Tue 2020-08-11 04:08PM

Thank you everyone for an excellent session :pray: :clap: