Hello community:
LASAIR website sent me here for help. The big picture is that I’m trying to get information on past transients so I can plan my filters well. I’m not finding good information on famous, well-documented ZTF transient hosts. What I’m hoping for is the host galaxy is _____, the link to the full catalog info is _____, and the ____colored mark on the aladdin image is what we’re referring to.
Here is what I can actually get:
For the most famous transient I can think of, “The Koala”, ZTF18abvkwla,
LASAIR - No diff image, a broken link to a host catalog name (no response at SDSS search; no idea how to find that)
ANTARES-No host info or diff image
ALerCE - Yes, diff image!, confusing set of host matches
ATserver - no host info
OTHER ALERTS:
ZTF19abvizsw, AT2019pim - nothing ANTARES, LASAIR, ALerCE
ZTF20aajnksq, AT2020blt - nothing ANTARES, LASAIR, ALerCE
ZTF 21aaeyldq/AT 2021any - ANTARES covers, no host info (LASAIR does NOT cover)
ZTF 21aayokph/AT 2021lfa- ANTARES covers, no host info, (LASAIR has no difference image, claims no host)
So, where do I go to get good host info? What am I doing that makes LASAIR so incomplete compared to other brokers? Did LASAIR only get going after 2021?
Thanks for joining the Forum and using it to request assistance from the Lasair developers. As Forum admin, I’ve updated the title a bit to be more representative of the topic of host association and also moved this post to the Lasair sub-category, so they’re sure to see it.
I’ll let the Lasair representatives address any potential differences between what Lasair covers, with respect to other brokers (attention @roy).
But as far as the broken link to the SDSS host on the ZTF18abvkwla page in Lasair, that’s an easy fix. I can see that there’s a typo in the hotlink:
Perhaps I can also help to address the question “So, where do I go to get good host info?”. I work on supernovae too, and host association is a scientifically challenging endeavor. I’m not sure what ZTF provides in the alert packets in terms of cross-matches to static-sky sources for brokers to use. But I can say that in the future, LSST will provide the nearest three stars, nearest three galaxies, and the nearest low-z galaxy (DMTN-151). I think it’s also the case that most brokers are planning their own static-sky cross-matches, and that at the moment, this service is probably a work in progress for all brokers. However, especially at higher redshifts and for transients without spectroscopic classifications, host association can always have some level of ambiguity that probabilistic analyses will need to account for.
First let me say that Lasair is built for rapid response to emerging transients. The one you quote – ZTF18abvkwla – is over six years old, and a lot has changed with the ZTF survey and schema in that time, and there has been trouble with cutout images. I am sorry that we are not aware of what you think is a better name (Koala): we do not know which transients are “famous” or “well-documented”.
I have made you a sample filter here which finds recent bright supernovae that are in TNS, with full information about the host galaxy. You can do “Run Filter” for results, or “Duplicate Filter” to make your own version. There is more information about building filters here.
But perhaps you want supernovae coincident with a specific set of galaxies that you already know? You can make a “watchlist” of up to a million, build a filter, and have coincident alerts streamed to you, see here