Little Red Dots

Before class: do a bit of homework

Before class: do a bit of homework

One of the hottest topics in astronomy these days is the nature of the Little Red Dots (LRDs, for short). Just what are they, and who first gave them this name? Your first task is to find the earliest appearance of this phrase:

Task 1: Use the Astrophysics Data System or any other tool of your choice to find the earliest paper that uses the phrase "little red dots" in its title. When was it published?
Bonus for any earlier papers in which the phrase "little red dots" appears in the abstract or body of the text, but not in the title.

One resource that I recommend highly for basic introductions to complicated astronomical topics is astrobites. This site is a collection of summaries and reports on recent astronomical papers, written by graduate students. Their goal is to explain the main results of these papers to an audience of not-yet-expert readers: interested laymen and other astronomy students, both undergraduate and graduate. I find many of these articles an excellent way to begin learning about some new topic that comes up in the course of my research, or just happens to catch my eye.

Task 2: Search on astrobites for an article with "Little Red Dots" in its title.
1. What published paper is this article summarizing? Provide the first author's name, title, journal, and year.
2. Based on this summary, what is a "little red dot?"
3. Examine the two panels of Figure 2 from the astrobites summary, which are taken from Figures 5 and 6 in the original paper. Be ready to explain the meaning of these figures in class.

In class, we will discuss the paper mentioned by the astrobites article, as well as more recent papers about Little Red Dots.

We will also spend a bit of time getting ready for the first set of student presentations in the final weeks of class.

Task 3: Bring any notes you've made so far on your topic to class. Be ready to show, either on a laptop or in hardcopy form, the references you will be using for your preparations.

Why are they called "Little Red Dots?"

Lower-right panel of Figure 1 in Kokorov, V., et al., ApJ 968, 38 (2024)

So what's the problem?

Figure 5 taken from Kokorov, V., et al., ApJ 968, 38 (2024)

Figure 1 taken from Furtak, L. J., et al., ApJ, 952, 142 (2023)

Figure 1 taken from Juodzbalis, I., et al., Nature 653, 1017 (2026)

Figure 2 taken from Juodzbalis, I., et al., Nature 653, 1017 (2026)

For more information

Some papers on the topic of little red dots
- Langeroodi, D., and Hjorth, J., ApJ 957, L27 (2023) is one of the earliest papers to place the term in its title.
- Kokorov, V., et al., ApJ 968, 38 (2024) describes a census of LRDs in JWST images.
- An entry in "astrobites" explaining the main points in Kokorov et al. provides a good introduction to LRDs.
Ned Wright's Cosmology Calculator provides relationships between redshift, age, several measures of distance, and more, for any given cosmological parameters.