A near-IR survey of luminous asymptotic giant branch stars in the satellites and stellar halo of M31

Abstract

We investigate the dwarf spheroidal (dSph) satellites and stellar halo of M31 using near-infrared imaging from the Wide-Field Camera on the UKIRT 3.8 m telescope. Our homogeneous analysis covers the stellar extents of 12 dSphs, as well as their surrounding halo field populations. We identify carbon-rich (C) and oxygen-rich (M) thermally-pulsing AGB stars (TP-AGBs) using colour-magnitude and colour-colour diagrams, which also allows for effective contaminant rejection. TP-AGB stars are detected in eight of the 12 dSphs, indicating small intermediate-age populations in a substantial fraction of the sample; they are also found in considerable numbers throughout most of M31's stellar halo. By combining 316 new detections with a revised classification of objects previously reported in the literature, we increase the TP-AGB candidate population in the dSphs from 82 to 359. We use the resulting dSph and halo AGB samples to compute C/M ratios and infer metallicities in the dSphs and adjacent halo fields with non-zero AGB counts. A clear metallicity gradient is observed in the M31 stellar halo out to ~150 kpc, consistent with that found using other tracers. Using literature star formation histories from main-sequence turn-off photometry, we find a tight correlation between the number of C stars in the dSphs and the stellar mass formed in the last 0.5--3 Gyr. This study underscores the promise of AGB stars as quantitative tracers of intermediate-age star formation, particularly in intrinsically faint systems, and provides a catalogue of candidate TP-AGB stars for follow-up.

CHASE Spectral Survey I: Measuring Contamination in the Color-selected J-region Asymptotic Giant Branch Distance Indicator
Siyang Li, Alexei V. Filippenko, Arief Ahmad +11
arXiv21 Sep 2026PreprintarXiv licenceFull textCosmology GalaxiesarXiv
Investigating the formation of small Solar System objects using stellar occultations by satellites: present, future and its use to update satellite orbits
Felipe Braga-Ribas, Frederic Vachier, Josselin Desmars +2
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences31 Aug 2026Peer-reviewedLicence not statedFull text10 citedPlanetary science & exoplanetsHAL
Exploring stellar evolution with Luminous Red Novae and Interacting Gap Transients
Nadejda Blagorodnova
arXiv1 Sep 2026PreprintarXiv licenceFull textHigh-energy astrophysics Solar & stellar physicsarXiv
A New Approach to Modeling Line Shapes with Quasi-H 2 + Satellites in Stellar Atmospheres
Jackson R. White, Thomas A. Gomez, Mark C. Zammit +6
The Astrophysical Journal30 Sep 2026Peer-reviewedCC BY 4.0Full textSolar & stellar physicsCrossref
Periodic activity on the (sub)millimetre surface of the asymptotic giant branch star Mira A
M. Andriantsaralaza, B. Bojnordi Arbab, W. Vlemmings +7
Astronomy & Astrophysics30 Oct 2026Peer-reviewedPublisher termsSolar & stellar physicsCrossref

Cite

BibTeX RIS

BibTeX

@misc{howell2026nearir,
  title = {{A near-IR survey of luminous asymptotic giant branch stars in the satellites and stellar halo of M31}},
  author = {Jess M. Howell and Annette M. N. Ferguson and Olivia C. Jones and Mike. J. Irwin and Maria-Rosa L. Cioni and Geraint F. Lewis and Nicolas. F. Martin and Alan. W. McConnachie},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.20810},
  eprint = {2609.20810},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.20810},
  note = {CC BY 4.0},
}

RIS

TY  - UNPB
TI  - A near-IR survey of luminous asymptotic giant branch stars in the satellites and stellar halo of M31
AU  - Jess M. Howell
AU  - Annette M. N. Ferguson
AU  - Olivia C. Jones
AU  - Mike. J. Irwin
AU  - Maria-Rosa L. Cioni
AU  - Geraint F. Lewis
AU  - Nicolas. F. Martin
AU  - Alan. W. McConnachie
PY  - 2026
DA  - 2026/09/17
PB  - arXiv
DO  - 10.48550/arxiv.2609.20810
UR  - https://arxiv.org/abs/2609.20810
AB  - We investigate the dwarf spheroidal (dSph) satellites and stellar halo of M31 using near-infrared imaging from the Wide-Field Camera on the UKIRT 3.8 m telescope. Our homogeneous analysis covers the stellar extents of 12 dSphs, as well as their surrounding halo field populations. We identify carbon-rich (C) and oxygen-rich (M) thermally-pulsing AGB stars (TP-AGBs) using colour-magnitude and colour-colour diagrams, which also allows for effective contaminant rejection. TP-AGB stars are detected in eight of the 12 dSphs, indicating small intermediate-age populations in a substantial fraction of the sample; they are also found in considerable numbers throughout most of M31's stellar halo. By combining 316 new detections with a revised classification of objects previously reported in the literature, we increase the TP-AGB candidate population in the dSphs from 82 to 359. We use the resulting dSph and halo AGB samples to compute C/M ratios and infer metallicities in the dSphs and adjacent halo fields with non-zero AGB counts. A clear metallicity gradient is observed in the M31 stellar halo out to ~150 kpc, consistent with that found using other tracers. Using literature star formation histories from main-sequence turn-off photometry, we find a tight correlation between the number of C stars in the dSphs and the stellar mass formed in the last 0.5--3 Gyr. This study underscores the promise of AGB stars as quantitative tracers of intermediate-age star formation, particularly in intrinsically faint systems, and provides a catalogue of candidate TP-AGB stars for follow-up.
ER  -

Abstract

Related

Cite