Rubin2020_PCW slack archives day2-tue-slot2e-rrb-galaxy-morphology 2020-07-31---2020-08-14

Fri 2020-07-31 08:13PM
@Melissa Graham has joined the channel
Melissa Graham Fri 2020-07-31 08:13PM
@Melissa Graham set the channel purpose: Rubin Research Bytes Session E. Galaxy Morphology
Melissa Graham Fri 2020-07-31 08:37PM
@Melissa Graham has renamed the channel from "day2-slot-2e-rrb-galaxy-morphology" to "day2-tue-slot2e-rrb-galaxy-morphology"
Melissa Graham Sat 2020-08-01 01:15PM
@Melissa Graham set the channel topic: Rubin Research Bytes Session E. Galaxy Morphology
RRB Webpage: <>
Wed 2020-08-05 02:11PM
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Thu 2020-08-06 12:36PM
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Fri 2020-08-07 10:15AM
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Fri 2020-08-07 07:52PM
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Sat 2020-08-08 07:08PM
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Mon 2020-08-10 06:44AM
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Mon 2020-08-10 10:17AM
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Nushkia Chamba Mon 2020-08-10 10:19AM
hey! I was asked to join this stack channel, I am one of the speakers for this session
Mon 2020-08-10 01:11PM
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Mon 2020-08-10 02:33PM
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Mon 2020-08-10 03:14PM
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Tue 2020-08-11 11:29AM
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Tue 2020-08-11 12:29PM
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Tue 2020-08-11 12:58PM
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Nushkia Chamba Tue 2020-08-11 01:16PM
ok something strange happened when i tried to join the meeting...
Nushkia Chamba Tue 2020-08-11 01:16PM
i got kicked out almost immedietely XD
Sugata Kaviraj Tue 2020-08-11 01:17PM
no worries could you exit the meeting and we'll try to reboot :slightly_smiling_face:
Sugata Kaviraj Tue 2020-08-11 01:17PM
we all got kicked out not sure why
Nushkia Chamba Tue 2020-08-11 01:17PM
maybe go to help
Tue 2020-08-11 01:18PM
@Jeff Carlin has joined the channel
Sugata Kaviraj Tue 2020-08-11 01:19PM
@channel we are having some issues with the zoom room at the moment. should be sorted out soon hopefully
Sugata Kaviraj Tue 2020-08-11 01:20PM
issue seems to be affecting all RRB zoom rooms
Benne Holwerda Tue 2020-08-11 01:21PM
Tue 2020-08-11 01:24PM
@Lucie Baumont has joined the channel
Tue 2020-08-11 01:25PM
@Frank Kenney has joined the channel
Benne Holwerda Tue 2020-08-11 01:25PM
It's up! Come join us!
Nushkia Chamba Tue 2020-08-11 01:28PM
sorry somehow i got kicked out again...
Frank Kenney Tue 2020-08-11 01:30PM
hey all
Benne Holwerda Tue 2020-08-11 01:34PM
post your questions here or in the zoom chat window.
Nushkia Chamba Tue 2020-08-11 01:41PM
ok my internet crashed and i got kicked out again
Nushkia Chamba Tue 2020-08-11 01:42PM
Benne Holwerda Tue 2020-08-11 01:42PM
It was a very cool result!
Nushkia Chamba Tue 2020-08-11 01:46PM
(if my connection dies again, I have asked @Sugata Kaviraj if he could present them on my behalf for the next section....?)
Nushkia Chamba Tue 2020-08-11 01:46PM
its very unstable since my home internet died today and i am using my mobile data
Benne Holwerda Tue 2020-08-11 01:57PM
that sucks. Well done for giving your talk.
Benne Holwerda Thu 2020-08-13 04:09PM
Hi sorry I should be using this.
Benne Holwerda Thu 2020-08-13 04:11PM
I am pulling assignments together (jupyter notebooks) and I use relatively small but useful tabulated data. I wanted to use the MNRAS paper's table but of course I can't get to it.
Benne Holwerda Thu 2020-08-13 04:12PM
I will be using your work for class :smile:
Nushkia Chamba Fri 2020-08-14 06:00PM
thats awesome! I am very happy to hear that. Why can't you access the data table? Is it not free? :confused: I can send it to you if you send me an email:
Nushkia Chamba Tue 2020-08-11 01:45PM
Antonio Vazquez Tue 2020-08-11 01:47PM
For Cristobal,
You have to be careful with early galaxies in deep images, because most of them have LSB structures around, like tidal structures that sometimes these look like disks. Are you taking this into consideration?
Cnmoya Tue 2020-08-11 02:47PM
Not as of now, given that our images are not really that deep. Eventually we can include it by toying with the input models for our "cube"
Antonio Vazquez Wed 2020-08-12 12:28PM
Yeah, I think this could be very useful when applying your model to Ruby images.
Thank you!
Melissa Graham Tue 2020-08-11 01:49PM
@here new transition time 11:15am due to technical difficulties
Dan Taranu Tue 2020-08-11 01:57PM
For Cristobal, what is the benefit of pre-computing the full grid of models? Is it to evaluate them all in parallel on a GPU? Otherwise it seems like it will scale badly - three parameters (size, ellipticity, position angle) is 512 models for a very coarse 8x8x8 grid, which is more model evaluations than you'd normally need to minimize chi^2 in serial.
Cnmoya Tue 2020-08-11 02:46PM
Yes, the parallelism is one reason. We also do it this way to move the convolution away from the fitting process and into the preprocessing.
Benne Holwerda Tue 2020-08-11 02:02PM
Chamba: How does Re compare to R1?
Nushkia Chamba Tue 2020-08-11 02:11PM
in which sense?
Nushkia Chamba Tue 2020-08-11 02:12PM
in dispersion in the size-stellar mass plane, r1 produces a scatter 3 times smaller than with Re, in slopes, R1 shows a stronger correlation overall with mass and higher slopes, in terms of location in the galaxy they are also very different! r1 captures galaxy boundaries and Re, light concentration.
Karen Masters Tue 2020-08-11 02:03PM
I wondered about the systematics introduced by using stellar mass models to compute galaxy sizes. Will galaxies with younger pops have different systematics than older ones?
Nushkia Chamba Tue 2020-08-11 02:14PM
hi Karen, thanks for your question, we are using a colour-stellar mass to light ratio relations, and I also compared the masses I computed using the Maraston et al. (2013) catalogue where they used a completely different method. And we have good agreement, max different is 0.25 dex!
Nushkia Chamba Tue 2020-08-11 02:14PM
The relations we used are from Roediger & Courteau (2015)
Nushkia Chamba Tue 2020-08-11 02:15PM
you will find these details in our paper Trujillo, Chamba & Knapen (2020). and i remind you as well, we are exploring a proxy for the threshold
Nushkia Chamba Tue 2020-08-11 02:16PM
and this proxy we chose specifically using MW-like objects, ofcourse the proxy will change depending on the galaxy and how efficient they are in forming stars, this is something I am exploring now in ongoing work :slightly_smiling_face:
Karen Masters Wed 2020-08-12 03:19PM
Thanks for the answer.
Dan Taranu Tue 2020-08-11 02:07PM
Good talks everyone :clap:
Benne Holwerda Tue 2020-08-11 02:22PM
Hello, Send me your questions either here or on the zoom chat!
Jeff Carlin Tue 2020-08-11 02:39PM
Q for Nushkia: How sensitive is the determination of R_1 to background subtraction? Is that radius typically near the sky background level?
Nushkia Chamba Tue 2020-08-11 02:52PM
this was answered live :slightly_smiling_face: but for those interested: we did characterise the effect on sky subtraction in our paper. The short answer is that the sensitively depends on the galaxy as our measurement depends on the colour of the galaxy. you will find all the details in the paper Trujillo, Chamba & Knapen (2020). :slightly_smiling_face: Typicall R1 is around 27-28 mag/arcsec^2 but can be fainter or brighter depending on the stellar pop. of the galaxy.
Nushkia Chamba Tue 2020-08-11 02:46PM
sorry I forgot to say, if you are interested to talk to me more about my work, feel free to connect with me here on Slack! :slightly_smiling_face:
Sugata Kaviraj Tue 2020-08-11 02:47PM
@channel thanks to all our speakers for your fantastic talks and to our audience for your questions! :slightly_smiling_face: