The DECam MAGIC Survey : Uncovering the Tidal Tails of the Crater II Dwarf Galaxy

Atzberger, K. R.; Pace, A. B.; Kallivayalil, N.; Chiti, A.; Erkal, D.; Cerny, W.; Limberg, G.; Placco, V. M.; Prabhu, D. S.; Stringfellow, G. S.; Vivas, A. K.; Chaturvedi, A.; Ferguson, P. S.; Riley, A. H.; Sand, D. J.; Carlin, J. L.; Choi, Y.; Crnojević, D.; Drlica-Wagner, A.; Ji, A. P.; Li, T. S.; Martínez-Vázquez, C. E.; Medina, G. E.; Noël, N. E.D.; Walker, A. R.; Carballo-Bello, J. A.; James, D. J.; Mutlu-Pakdil, B.; Navabi, M.; Sakowska, J. D.

The DECam MAGIC Survey : Uncovering the Tidal Tails of the Crater II Dwarf Galaxy

Mark

Atzberger, K. R. ; Pace, A. B. ; Kallivayalil, N. ; Chiti, A. ; Erkal, D. ; Cerny, W. ; Limberg, G. ; Placco, V. M. ; Prabhu, D. S. and Stringfellow, G. S. , et al. (2026) In Astrophysical Journal 1006(2).

Abstract: Crater II (CraII), a large and low-density dwarf spheroidal galaxy, has unusual observed properties that are difficult to reproduce in cold dark matter simulations. Ongoing tidal disruption may help explain the discrepancies, as evidenced by the recent discovery of tidal tails. Here we present metallicity-sensitive narrowband photometry of the Ca II H and K lines from the Dark Energy Camera, covering 128 deg² across the center and identified tidal tails of CraII as part of the Mapping the Ancient Galaxy in CaHK survey. Our combined photometric metallicity, color–magnitude, proper motion, and parallax selections identify 162 CraII candidates. Of these, 37 candidates are located in the tidal tails, which extend at least 7° (∼95... (More); Crater II (CraII), a large and low-density dwarf spheroidal galaxy, has unusual observed properties that are difficult to reproduce in cold dark matter simulations. Ongoing tidal disruption may help explain the discrepancies, as evidenced by the recent discovery of tidal tails. Here we present metallicity-sensitive narrowband photometry of the Ca II H and K lines from the Dark Energy Camera, covering 128 deg² across the center and identified tidal tails of CraII as part of the Mapping the Ancient Galaxy in CaHK survey. Our combined photometric metallicity, color–magnitude, proper motion, and parallax selections identify 162 CraII candidates. Of these, 37 candidates are located in the tidal tails, which extend at least 7° (∼95 kpc) from the center of CraII, suggesting it has lost ≳25% of its initial stellar mass. We confirm low contamination rates with dedicated control fields and highlight the extremely low surface brightness stellar features that can be uncovered with CaHK data, as faint as ∼36 mag arcsec⁻². We also make the first detection of a metallicity gradient (−0.34 ± 0.17 dex deg⁻¹) in the center of the galaxy and infer a stream width of w ∼ 0 (Formula presented) .° 8, roughly 50% larger than the CraII half-light radius. The detection of candidates in the most distant CraII pointings from its center implies that the tidal tails extend beyond our footprint. We compare the CraII stream to N-body models with “cored” and “cuspy” dark matter halo progenitors, determining that CraII’s density profile is still ambiguous and warrants further modeling.
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Please use this url to cite or link to this publication: https://lup.lub.lu.se/record/5b5c3b1f-17bc-424c-b0cd-99231b2df284

author

Atzberger, K. R. ; Pace, A. B. ; Kallivayalil, N. ; Chiti, A. ; Erkal, D. ; Cerny, W. ; Limberg, G. ; Placco, V. M. ; Prabhu, D. S. and Stringfellow, G. S. , et al. (More)

Atzberger, K. R. ; Pace, A. B. ; Kallivayalil, N. ; Chiti, A. ; Erkal, D. ; Cerny, W. ; Limberg, G. ; Placco, V. M. ; Prabhu, D. S. ; Stringfellow, G. S. ; Vivas, A. K. ; Chaturvedi, A. ; Ferguson, P. S. ; Riley, A. H. ^LU

; Sand, D. J. ; Carlin, J. L. ; Choi, Y. ; Crnojević, D. ; Drlica-Wagner, A. ; Ji, A. P. ; Li, T. S. ; Martínez-Vázquez, C. E. ; Medina, G. E. ; Noël, N. E.D. ; Walker, A. R. ; Carballo-Bello, J. A. ; James, D. J. ; Mutlu-Pakdil, B. ; Navabi, M. and Sakowska, J. D. (Less)

author collaboration

MAGIC & DELVE Collaborations

organization

Astrophysics

publishing date

2026-08-01

type

Contribution to journal

publication status

published

subject

Astronomy, Astrophysics and Cosmology

keywords

Dark matter distribution (356), Dwarf galaxies (416), Local Group (929), Low surface brightness galaxies (940), Narrow band photometry (1088), Stellar streams (2166)

in

Astrophysical Journal

volume

1006

issue

2

article number

180

publisher

American Astronomical Society

external identifiers

scopus:105045773910

ISSN

0004-637X

DOI

10.3847/1538-4357/ae7f1f

language

English

LU publication?

yes

id

5b5c3b1f-17bc-424c-b0cd-99231b2df284

date added to LUP

2026-10-01 13:21:00

date last changed

2026-10-01 13:21:40

@article{5b5c3b1f-17bc-424c-b0cd-99231b2df284,
  abstract     = {{<p>Crater II (CraII), a large and low-density dwarf spheroidal galaxy, has unusual observed properties that are difficult to reproduce in cold dark matter simulations. Ongoing tidal disruption may help explain the discrepancies, as evidenced by the recent discovery of tidal tails. Here we present metallicity-sensitive narrowband photometry of the Ca II H and K lines from the Dark Energy Camera, covering 128 deg<sup>2</sup> across the center and identified tidal tails of CraII as part of the Mapping the Ancient Galaxy in CaHK survey. Our combined photometric metallicity, color–magnitude, proper motion, and parallax selections identify 162 CraII candidates. Of these, 37 candidates are located in the tidal tails, which extend at least 7° (∼95 kpc) from the center of CraII, suggesting it has lost ≳25% of its initial stellar mass. We confirm low contamination rates with dedicated control fields and highlight the extremely low surface brightness stellar features that can be uncovered with CaHK data, as faint as ∼36 mag arcsec<sup>−2</sup>. We also make the first detection of a metallicity gradient (−0.34 ± 0.17 dex deg<sup>−1</sup>) in the center of the galaxy and infer a stream width of w ∼ 0 (Formula presented) .° 8, roughly 50% larger than the CraII half-light radius. The detection of candidates in the most distant CraII pointings from its center implies that the tidal tails extend beyond our footprint. We compare the CraII stream to N-body models with “cored” and “cuspy” dark matter halo progenitors, determining that CraII’s density profile is still ambiguous and warrants further modeling.</p>}},
  author       = {{Atzberger, K. R. and Pace, A. B. and Kallivayalil, N. and Chiti, A. and Erkal, D. and Cerny, W. and Limberg, G. and Placco, V. M. and Prabhu, D. S. and Stringfellow, G. S. and Vivas, A. K. and Chaturvedi, A. and Ferguson, P. S. and Riley, A. H. and Sand, D. J. and Carlin, J. L. and Choi, Y. and Crnojević, D. and Drlica-Wagner, A. and Ji, A. P. and Li, T. S. and Martínez-Vázquez, C. E. and Medina, G. E. and Noël, N. E.D. and Walker, A. R. and Carballo-Bello, J. A. and James, D. J. and Mutlu-Pakdil, B. and Navabi, M. and Sakowska, J. D.}},
  issn         = {{0004-637X}},
  keywords     = {{Dark matter distribution (356); Dwarf galaxies (416); Local Group (929); Low surface brightness galaxies (940); Narrow band photometry (1088); Stellar streams (2166)}},
  language     = {{eng}},
  month        = {{08}},
  number       = {{2}},
  publisher    = {{American Astronomical Society}},
  series       = {{Astrophysical Journal}},
  title        = {{The DECam MAGIC Survey : Uncovering the Tidal Tails of the Crater II Dwarf Galaxy}},
  url          = {{http://dx.doi.org/10.3847/1538-4357/ae7f1f}},
  doi          = {{10.3847/1538-4357/ae7f1f}},
  volume       = {{1006}},
  year         = {{2026}},
}

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The DECam MAGIC Survey : Uncovering the Tidal Tails of the Crater II Dwarf Galaxy