iiinova — where your digital self keeps evolving

Anke Ardern-Arentsen @ankeaa.bsky.social · 02/09/2026

Submitted a paper that's been almost 10 years in the making! First PIGS photometric observations early 2017, photometric survey finished in 2023, several calibrations & recalibrations, many spectroscopic follow-up observations... Almost ready for the public release! 🔭✨🐷

Screenshot of the LaTeX paper title: "The Pristine Inner Galaxy Survey (PIGS) XII: Photometric data release and follow-up strategy for 4MOST"

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Anke Ardern-Arentsen @ankeaa.bsky.social · 13/08/2026

We had a bit of a scare with a thunderstorm ~1.5h before the eclipse, but it cleared up and it was so amazing! 🔭 🤩 And what a joy to watch it together with many other astronomers (attending the APOGEE/Majewski fest @ Teruel) - cheers and applause at totality!

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Anke Ardern-Arentsen @ankeaa.bsky.social · 01/10/2025

Before being locked in a basement at the TNG offices for two days of WEAVE Science Processing & Analysis meeting (my first as part of the CASU team!), I managed to check out the southernmost tip of La Palma 🌋

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Anke Ardern-Arentsen @ankeaa.bsky.social · 11/06/2025

Nice view of the Sun 🌞 today from @cambridgeastro.bsky.social - thanks to Robin Catchpole 🔭

Picture of a TV screen showing the Sun through an H-alpha filter. Some nice solar prominences can be seen on the upper right

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Anke Ardern-Arentsen @ankeaa.bsky.social · 08/05/2025

Such a good view for a meeting room, and the view at the dinner was amazing too 😍 @ Pristine collaboration meeting, Nice Observatory @obscoteazur.bsky.social

A view of Nice city and the Mediterranean sea, framed by a window inside the Observatory library. There are clouds in the sky and some raindrops on the window, but the view is amazing.

View of Nice by night, with many city lights below and still some sunset colours in the sky. Taken from Nice observatory, near the big dome (not visible)

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Anke Ardern-Arentsen @ankeaa.bsky.social · 03/04/2025

For a recent outreach talk I created this visualisation of real stellar spectra (from the LAMOST survey) - showing a metal-rich, a very metal-poor, and a carbon-enhanced very metal-poor star with similar temperatures (~5000K). Look at those massive molecular carbon bands for the CEMP star! ✨🔭

The image shows three spectra from top to bottom (metal-rich, very metal-poor and carbon-enhanced very metal-poor, respectively), with each wavelength visualised by a coloured vertical line. The axis goes from ~380-700 nanometers. The metal-rich star has more and stronger dark lines than the metal-poor star, corresponding to absorption features. The carbon-enhanced metal-poor star has massive absorption bands, corresponding to molecular carbon absorption.

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Anke Ardern-Arentsen @ankeaa.bsky.social · 15/03/2025

I love singing with the #Cambridge University Gospel #Choir 😍 so enjoyed our concert at Great St Mary’s tonight! 🎶

All 21 choir members that participated in the concert, smiling and doing some spontaneous movements for the photo. We are wearing black & white and red scarves. The photo is taken in the front of Great St Mary’s Church.

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Anke Ardern-Arentsen @ankeaa.bsky.social · 04/03/2025

Having fun with a CD spectroscope and my old office desk lamp! Getting ready for the school kids visiting later this week for International Women’s Day ✨ 🔭

Picture of a spectrum of my desk lamp through the spectroscope slit. Distinct coloured lines can be seen

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Anke Ardern-Arentsen @ankeaa.bsky.social · 06/02/2025

Paper now published! 🎉 There are two fun new figures, showing how carbon-enhanced stars are offset from normal stars in the CMD (not a new result, but neat to see with this data) ✨ academic.oup.com/mnras/articl... (incl. mention to colour in figure descriptions...)

Gaia colour absolute-magnitude diagram for very metal-poor RGB stars, where carbon-rich stars (identified using Gaia XP, see the paper) are colour-coded by their carbon abundance. Carbon-rich stars follow a redder RGB sequence than carbon-normal stars.

Gaia colour absolute-magnitude diagram for very metal-poor (left), intermediate metal-poor (middle) and metal-poor (right) stars in our spectroscopic reference sample, where carbon-rich stars are colour-coded by their carbon abundance. Carbon-rich stars follow a redder RGB sequence than carbon-normal stars.

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Anke Ardern-Arentsen @ankeaa.bsky.social · 21/11/2024

Having a wonderful time at #IAUS395, the “Stellar Populations in the Milky Way and Beyond” symposium in Paraty, Brazil 🤩 Both scientifically and otherwise a great meeting, celebrating the career of Beatrice Barbuy 🔭✨

Several small boats floating on a blue sea near a beach and green foresty hills

A narrow touristy street with large cobblestones on a warm summer evening

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Anke Ardern-Arentsen @ankeaa.bsky.social · 16/10/2024

🔭🌟 Paper day! We're using the low-res Gaia XP spectra to derive metallicities and carbon abundances, focusing on metal-poor, *very* carbon-rich stars! These probe binary interactions & the very First Stars. Here are a few of the highlight figures (see alt text for details) arxiv.org/abs/2410.11077

the top part of the figure shows three synthetic spectra with different carbon abundances, and the bottom part shows Gaia XP low-resolution spectra for carbon-normal and carbon-rich stars. It is clear that carbon-rich stars can be identified from these spectra

distribution of metallicity [Fe/H] and carbon abundance [C/Fe] for a high-quality giant star sample. There is a "main sequence" around [C/Fe] = 0 and a big cloud of carbon-rich objects up to [C/Fe] = 2.5. The orange and red lines divide different groups of C-rich stars, with most of them being in "Group I" - formed by binary interactions with an AGB companion.

$The figure shows the fraction of C-rich stars as function of metallicity. We used two different definitions, the "classical" CEMP definition of [C/Fe] > 0.7 and one based on whether stars are >3sigma outliers from the main distribution. One interesting thing is that our fraction of C-rich stars for -3.0 < [Fe/H] < -2.0 is much lower than in any other literature sample, and it does not keep rising as for higher metallicities. There are many things to say about this figure but you might want to read the paper :)$ $We also tested how the C-rich fraction changes as function of the orbital energy in the Milky Way, or in other words, how tightly bound the stars are to our Galaxy. For very metal-poor (VMP) stars, there is a strong trend, where more bound stars (those in the inner Galaxy) have a lower fraction of C-rich stars. This suggests a difference in the binary population in different Galactic environments! We suggest it might be connected to the contribution of globular clusters.$

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Anke Ardern-Arentsen @ankeaa.bsky.social · 31/08/2024

I had to look twice when I spotted this drycleaners shop in Tauranga, NZ! I wonder who designed their Pristine logo first 🤔✨🧺

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Anke Ardern-Arentsen @ankeaa.bsky.social · 11/05/2024

Never thought the first time I’d see the aurora would be from my bedroom window in Cambridge!! 🤩🤩

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Anke Ardern-Arentsen @ankeaa.bsky.social · 17/04/2024

Accepted version now on arXiv 🎉🤩 With a few new figures, supporting our previous findings: evidence for two distinct halo components in the inner few kpc of the Galaxy - one faster rotating & lower dispersion, and a more diffuse, almost stationary component arxiv.org/abs/2312.03847

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Anke Ardern-Arentsen @ankeaa.bsky.social · 08/12/2023

3) comparing with other studies of the ancient (inner) Milky Way, we interpret this confined, slightly rotating metal-poor population as a mix of early large Galactic building blocks (more important at higher metallicity) and smaller accretion events (lower metallicity). [4/5]

Energy versus angular momentum for 4 metallicity groups in PIGS. Most of the stars have very high energies, consistent with them being very bound to the inner Galaxy. They get less bound for lower metallicities. Two comparison lines are also shown, showing that most stars in PIGS are below the "Heracles line" and almost all stars are below the "Aurora line". This is just a comparison and does not mean that these are accreted/in-situ respectively.

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Anke Ardern-Arentsen @ankeaa.bsky.social · 08/12/2023

2) we also find that Galactic rotation decreases with metallicity, but that the most metal-poor stars do have some net rotation (~ 40 km/s) around the Galactic centre. [3/5]

Azimuthal velocity as a function of metallicity for the PIGS sample. The velocity decreases with decreasing metallicity, but flattens below [Fe/H] < -2.0 and remains above zero.

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Anke Ardern-Arentsen @ankeaa.bsky.social · 08/12/2023

In this paper, we study (what we believe to be) the oldest stars in the Milky Way. We find that 1) many of the most metal-poor stars are very confined to the inner region of our Galaxy. 60% of the VMP stars currently there never go beyond 5 kpc from the centre! [2/5]

$The fraction of stars in the PIGS sample that has their orbits confined within a given distance (10, 5 or 3.5 kpc) from the Galactic centre as a function of metallicity. It decreases with decreasing metallicity, and flattens for [Fe/H] < -2.0.$

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Anke Ardern-Arentsen @ankeaa.bsky.social · 08/12/2023

🔭 Paper day! "🐷🐷🐷🐷🐷🐷🐷🐷: Characterising the orbital properties of the ancient, very metal-poor inner Milky Way" - arxiv.org/abs/2312.03847 - it's been years in the making, & I'm so relieved to have submitted it! A short paper thread: [1/5]

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Anke Ardern-Arentsen @ankeaa.bsky.social · 22/11/2023

🔭 We suggest that many of the previous identifications of “discy VMP stars” in the Milky Way could be explained by the presence of a prograde halo population, and find no evidence of a significant VMP disc population (in our sample). There are some nice figures in the paper, including this one:

From high metallicity (bottom right) to low metallicity (top left), a transition can be seen in the vR (velocity in the radial direction) versus vphi (velocity in direction of rotation) space - a disc component is clearly present at high metallicity, but disappears in the lowest metallicity bins, where only halo-like stars are left.

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Anke Ardern-Arentsen @ankeaa.bsky.social · 12/09/2023

It’s been a couple of weeks since I get to carry this r-process-enhanced ring on my finger! Happy to have merged with my binary companion 🥰

Photo of my wedding ring on our wedding day, with my hand on my husbands shoulder. Our faces aren’t visible, and there is a hint of my bouquet.

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