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Unveiling M33's Hidden Merger History: A Potential Population of Star Clusters on Retrograde Orbits

T0 review · 4 major / 4 minor · reviewed 2026-08-06 · deepseek-v4-flash

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Pith's one-line read Star clusters on retrograde orbits reveal that M33 has accreted dwarf galaxies.

desk verdict Plausible but not yet robust: the retrograde cluster claim in M33 depends on unverified disk membership and one extreme object, though the old metal-poor group is genuinely worth attention. read the letter →

arxiv 2507.13488 v1 pith:OQDFQH4Y submitted 2025-07-17 astro-ph.GA

Borja Anguiano , Geraint F. Lewis , Steven R. Majewski This is my paper
classification astro-ph.GA
keywords M33TriangulumGalaxyretrogradestarclustersmergersaccretionhistoryglobularclusterkinematicsgalacticwarpLocalGroup
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

The paper aims to show that M33, usually regarded as a quiet, isolated spiral, has a hidden merger history recorded in its globular cluster system. Combining radial velocities from published surveys, it identifies fifteen clusters whose deprojected orbits go backwards relative to the disk, with a probability of less than one in a thousand that this is chance. It interprets these retrograde clusters as the remains of one or more dwarf galaxies accreted by M33, and uses the cluster count to estimate a lower limit of about ten percent for the accreted fraction of the halo's virial mass. If the interpretation is right, an accretion event, rather than only tides from M31, could explain the pronounced warp in M33's disk. The reader should care because this turns a supposedly uneventful galaxy into a test case for how dwarf accretion shapes disk galaxies in the Local Group.

What carries the argument

The central object is the vertical component of the angular momentum $L_z = -V_{\rm rot} R$, with the sign chosen so that prograde orbits are positive. Because only sky positions and line-of-sight velocities are available, the paper deprojects them into rotational velocities with $V_{\rm rad} = V_0 + V_{\rm rot}\sin\xi\cos\theta$, using M33's position angle (22.5 degrees) and inclination (54 degrees). A cluster counts as retrograde when $-L_z + 2\sigma_{L_z} < 0$, which filters out statistically insignificant negative velocities. Pseudo-Lindblad diagrams (kinetic energy versus $L_z$) and an age-metallicity relation then separate the retrograde candidates into accreted groups, and the globular-cluster count versus halo-mass correlation converts the number of candidates into a lower limit on accreted virial mass.

What would settle it

Take the fifteen retrograde clusters and measure their distances and proper motions, which the paper notes is presently only accessible with JWST. If their three-dimensional velocities show they are on pressure-supported halo orbits rather than corotating with the disk, the retrograde classification is an artifact of the deprojection assumption; if the orbits instead lie in a disk plane with the opposite sense of rotation, the accretion interpretation is confirmed. A cheaper check is to search for additional M33 clusters beyond 30 kpc: the paper's interloper scenario predicts roughly 100 to 200 halo globular clusters in that volume, which panoramic surveys could verify or rule out.

Watch

Extended reading notes

Core claim

The paper argues that, of 145 star-cluster candidates in and around M33 with measured radial velocities, 15 rotate opposite to the disk at more than 2-$\sigma$ significance; the probability of even 10 such objects at that significance is 0.06 percent. Five are bona fide globular clusters confirmed by resolved Hubble Space Telescope photometry, and four of them (U49, [SSA2010]1566, H38, H33B) form an old, metal-poor group at large radii that the paper interprets as debris from an early accretion event, with M33-EC2 grouped alongside them. Because the gas (HII regions) shows no statistically significant retrograde motions, the retrograde clusters are not simply the tail of a population with large velocity errors. Under the assumption that all clusters belong to the disk, the paper estimates that the accreted material makes up at least $M_{\rm vir} \sim (7 \pm 3) \times 10^{10}\,M_\odot$, about 10% of M33's halo mass, and suggests one such accretion event as the cause of the warp in M33's gas and stellar disk. One object, U77, has a retrograde velocity above the escape speed and an extended horizontal branch, so the paper proposes it may be a stripped dwarf spheroidal galaxy rather than a cluster.

Load-bearing premise

The analysis assumes every cluster lies in M33's disk and shares its rotation, so a measured radial velocity can be turned into a rotational velocity; if a meaningful share of the fifteen 'retrograde' clusters are actually halo objects on random orbits, their negative angular momenta are artifacts and the accretion conclusion loses its footing.

Editorial extensions

If this is right

  • M33's cluster system records at least one, and probably more, past accretion events; the old, metal-poor retrograde group is a candidate for a single early merger.
  • At least roughly 10% of M33's halo virial mass has an accreted origin, with a lower limit of $M_{\rm vir} \sim (7 \pm 3) \times 10^{10}\,M_\odot$.
  • The accretion hypothesis can explain the warp in M33's gas and stellar disk without requiring a close prior encounter with M31, which is consistent with proper-motion evidence suggesting M33 may be on first infall.
  • Some high-velocity objects previously catalogued as clusters, notably U77, may be unbound dwarf spheroidal galaxies, adding to M33's known satellite population.
  • Because the cluster population has a hotter velocity dispersion and lower $V_{\rm rot}/\sigma$ at large radii than the gas, some of the sampled clusters are probably halo objects, making proper-motion follow-up the decisive test.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • If the fifteen retrograde clusters are accreted debris, then by symmetry M33 should host a comparable number of accreted clusters now on prograde orbits, so the true accreted cluster population may be roughly twice the fifteen and the virial-mass lower limit is likely a conservative floor.
  • The same deprojection technique, applied to other Local Group galaxies such as M31 or the Magellanic Clouds, could yield a retrograde fraction that becomes a quantitative merger-history metric; the paper itself does not make that comparison.
  • If a single massive accretion caused the warp, the orbital poles of the retrograde clusters should cluster near the warp's line of nodes, a specific geometric prediction that full three-dimensional orbits could test.
  • The intermediate-age, metal-poor object U77, if confirmed as a dwarf spheroidal rather than a cluster, would be an unusually young accretion remnant and would strengthen the claim that M33 swallowed satellites until relatively recent times.
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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

4 major / 4 minor

Summary. The manuscript combines literature radial velocities for 142–145 star clusters in M33 with photometric and astrometric cleaning to search for retrograde orbits. Under the assumption that all clusters lie in a disk, the authors deproject radial velocities, define retrograde candidates by the condition -Lz + 2 sigma_Lz < 0, and identify 15 such clusters. They argue this population is statistically significant, group five old metal-poor objects as an accreted 'Old, Metal-Poor Group,' compare with E-MOSAICS simulations, and use the globular-cluster–halo-mass relation to estimate a lower limit M_vir ~ (7 +/- 3) x 10^10 M_sun, about 10% of M33's halo mass, which they associate with the disk warp. The authors explicitly acknowledge in Section 3.5 that the disk-membership assumption cannot be unambiguously verified with current data.

Significance. If the retrograde population is real, this would be a valuable and rare kinematic signature of accretion in M33 and would bear on the first-infall scenario and the origin of the warp. The paper's strengths include a careful literature compilation, explicit foreground removal using Gaia astrometry and photometry, a comparison with HII-region kinematics, and a candid caveat section. However, the central quantitative claims (the 15-cluster significance and the accreted-mass estimate) currently rest on the disk-membership assumption and on deprojection near the minor axis; the manuscript itself states that the disk-versus-halo question cannot be settled with present data. The claims are plausible but not yet demonstrated at the level required for publication.

major comments (4)
  1. [Section 3.1 / Table 1] U77's deprojected angular momentum (-Lz = -63,103 +/- 24,185 kpc km/s) is two orders of magnitude larger than every other entry in Table 1 and is produced by an extremely small major-axis coordinate (X ~ -7.9e-5), where the 1/cos(theta) factor in V_Rot = (V_Rad - V0)/(sin(i) cos(theta)) amplifies both the signal and the uncertainty without bound. Section 3.4 independently concludes that U77 is unbound and likely a dwarf spheroidal galaxy rather than a bound M33 cluster. Including U77 in the retrograde count and in the accreted-mass estimate is therefore not justified. The analysis should be repeated with U77 excluded, and also with other minor-axis objects and H38 (which is reported to exceed the escape velocity) excluded, and the sensitivity of the 15-object count to these choices should be reported.
  2. [Section 3.3] The significance calculation is not reproducible as written. The text reports 'the probability of seeing more than ten sources at >2 sigma (one-sided) out of a sample of 145 is 0.06%,' but the actual selection is the 15 clusters satisfying -Lz + 2 sigma_Lz < 0, and the sample size is given as 142 in Section 2 and 145 here. The p-value should be recomputed for the actual selection rule and sample size, under a null that propagates the 1/cos(theta)-amplified measurement uncertainties, which produce heavy-tailed Lz errors, and ideally includes a plausible halo-interloper contribution. Without this, the quoted 0.06% cannot be verified from the paper.
  3. [Section 3.1 / Section 3.5] The disk-membership assumption is load-bearing and is acknowledged by the authors to be unverifiable. Section 3.1 derives a cluster velocity dispersion of ~130 km/s, much hotter than the HII regions (~50 km/s), and notes that V_Rot/sigma_Rot decreases with radius, which already suggests the presence of a non-disk component. Section 3.5 then states that 'it is not possible unambiguously to identify whether the observed stellar clusters are purely a disk population, or whether it is contaminated by interlopers from the halo.' The subsequent argument that a 21% interloper fraction would require ~100-200 halo clusters is order-of-magnitude rather than a quantitative rejection. A Monte Carlo test that injects a pressure-supported halo population with the measured dispersion and recomputes the expected number of spurious retrograde classifications is needed to support the claim that 15 retrograde clusters signal accretion.
  4. [Section 4] The virial-mass lower limit M_vir ~ (7 +/- 3) x 10^10 M_sun uses the count of 15 retrograde clusters as the number of accreted globular clusters in a GC-halo-mass scaling relation. This is not a robust lower limit until the membership issues above are resolved: U77 may not be a cluster at all, some of the 15 may be projection-amplified minor-axis objects, others may be halo interlopers, and the uncertainty quoted from sqrt(N) in footnote 3 does not include these systematics. The authors should either restrict the mass estimate to a membership-verified subsample or present the estimate explicitly as conditional on the disk assumption, with the systematic uncertainty quantified.
minor comments (4)
  1. [Table 1 note] The quantity X = -7.9e-5 has no units; please specify whether it is in degrees, arcminutes, or kpc, and define how X/R is computed from the adopted position angle and inclination.
  2. [Section 3.3.1 / Figure 8] The text refers to a 'green dashed line,' a 'red line,' and a 'green line'; the two green lines should be distinguished in the figure or caption, and the parameters of the closed-box chemical evolution models should be stated in the text or a table.
  3. [Section 3.3] The sentence beginning 'M33B has alpha-element abundances...' appears to refer to H33B based on context and Table 1; please correct the object label.
  4. [Section 3.5] The paragraph beginning 'high-redshift galaxies often show irregular...' is not connected to the caveat about disk membership; either integrate it into the argument or remove it.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the retrograde population and accreted-mass estimate follow from external kinematics, a stated disk assumption, and an external scaling relation, with no step reducing to its own input.

full rationale

The paper's derivation chain is linear and self-contained: literature radial velocities (Chandar et al. 2002; Sharina et al. 2010; Beasley et al. 2015) are combined with a stated disk-geometry assumption (V_Rad = V0 + V_Rot sin i cos theta, Sect. 3.1) to produce V_Rot and Lz; a 2-sigma sign cut (-Lz + 2 sigma_Lz < 0) selects 15 retrograde clusters; a binomial null test quantifies significance; and the accreted virial mass is obtained by feeding the cluster count into an external GC-halo-mass scaling relation (Blakeslee et al. 1997; Spitler & Forbes 2009; Burkert & Forbes 2020). No equation in this chain is defined in terms of the conclusion, and no fitted parameter is reused as a prediction. The disk assumption and possible halo interlopers are explicitly acknowledged in Sect. 3.5 ('it is not possible unambiguously to identify whether the observed stellar clusters are purely a disk population, or whether it is contaminated by interlopers from the halo'), which is a stated limitation rather than a circular step. The U77 projection-amplification issue flagged in Table 1 and Sect. 3.4 (X = -7.9e-5, Lz = -63103 +/- 24185 kpc km/s) is a real robustness concern but not circularity: the paper does not redefine the retrograde criterion to force U77's inclusion; it reports the extreme value and notes the associated uncertainty. Self-citations (e.g., Law & Majewski 2010; Anguiano 2012) appear only in contextual or methodological remarks and are not load-bearing for the central claim.

Assumptions & free parameters 1 free parameters · 7 assumptions · 0 invented entities

The central claim rests primarily on the disk-membership assumption and the adopted M33 geometry; the mass estimate adds the external GC-virial mass correlation, and the significance test adds a Gaussian null model. The only free parameter introduced by the authors is the 2-sigma retrograde threshold. No new entities such as particles, forces, or dimensions are invented; U77 is reinterpreted as a candidate dwarf spheroidal galaxy but remains counted as a retrograde cluster.

free parameters (1)
  • Retrograde significance threshold = 2 sigma in -Lz (i.e., -Lz + 2 sigma_Lz < 0)
    Hand-chosen threshold in Section 3.3 that defines which clusters count as retrograde; it directly sets the count of 15 used in the significance test and the accreted mass estimate.
assumptions (7)
  • domain assumption All clusters in the sample lie in the disk of M33 and move with disk-like rotation.
    Stated in Section 3.1 and revisited in Section 3.5. The entire deprojection of radial velocities into rotational velocities and angular momentum depends on this; if false, apparent retrograde orbits can be produced for halo objects.
  • domain assumption The null hypothesis for retrograde counts uses a Gaussian distribution with one-sided greater-than-2-sigma tails.
    Section 3.3 computes a 0.06 percent probability of seeing more than ten 2-sigma outliers in 145 sources. Table 1 shows strongly non-Gaussian uncertainties from 1/cos(theta) amplification, so this null model is fragile.
  • domain assumption Adopted M33 geometry and systemic velocity: position angle 22.5 degrees, inclination 54 degrees, distance 840 kpc, systemic radial velocity -179 km/s.
    Used in Section 3.1 to compute X/R and rotational velocity. These literature values carry their own uncertainties that are not fully propagated into the final angular momentum statistics; systematic errors here change the retrograde classification.
  • domain assumption The escape-velocity model parameters approximate M33's gravitational potential: NFW halo of 3.7 x 10^11 solar masses with 20 kpc scale length, and Miyamoto-Nagai disks of 8 x 10^9 solar masses.
    Section 3.4. Used to conclude U77 is unbound; if the potential is even moderately different, U77's status and its inclusion as a retrograde cluster change.
  • domain assumption The globular cluster number versus virial mass correlation applies to M33's accreted clusters.
    Section 4 uses this external calibration to convert the retrograde cluster count into a virial mass of about 7 x 10^10 solar masses. The intrinsic scatter and applicability to a low-mass disk galaxy are assumed.
  • domain assumption The retrograde clusters are not significantly contaminated by Milky Way foreground stars after the Gaia and color-color removals.
    Section 2 describes removing objects via parallax, proper motion, color-color sequence, and BP/RP excess factor. The completeness of these foreground rejection criteria is assumed; residual contamination would change the retrograde count.
  • domain assumption Simple closed-box chemical evolution models with constant star formation describe the M33 age-metallicity relation.
    Figure 8 interprets age-metallicity sequences using these models; the authors stress the curves are not fits. This supports the accretion interpretation but is not load-bearing for the retrograde discovery itself.

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Cite this review

Pith. "Pith review of Unveiling M33's Hidden Merger History: A Potential Population of Star Clusters on Retrograde Orbits." pith.science (2026). https://pith.science/paper/OQDFQH4Y

@misc{pith2026250713488,
  author       = {Pith},
  title        = {Pith review of: Unveiling M33's Hidden Merger History: A Potential Population of Star Clusters on Retrograde Orbits},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/OQDFQH4Y}},
  note         = {Machine review of arXiv:2507.13488}
}
abstract

We report the discovery of a possible sub-population of stellar clusters that appear to follow retrograde orbits around the third largest galaxy in the Local Group, M33 (Triangulum). This spiral disk galaxy has apparently had a mostly quiescent existence, although recent discoveries, particularly of a pronounced warp in the gas and stellar disk, suggest that M33's relatively quiet past was interrupted at least once by a dynamical interaction with another galaxy. We suggest that this sub population provides evidence of accretion of one or more dwarf galaxies in M33's history. We estimate a lower limit for the accreted halo virial mass of $M_{\rm vir} \sim (7 \pm 3) \times 10^{10}$\msun, accounting for about 10\% of the virial mass in the halo of M33 that has an accretion origin. We propose one of these accretion events as the source of the observed warp in M33's disk.

Figures

Figures reproduced from arXiv: 2507.13488 by the authors.

Figure 1
Figure 1. Left panel: The (𝑟 ′ - 𝑖 ′ ) - (𝑔 ′ - 𝑟 ′ ) colour-colour diagram showing potential MW objects previously classified as M33 clusters (green stars) that we have removed according to the criteria described in Section 2. Yellow circles indicate bona fide globular clusters based on Hubble Space Telescope (HST) imaging. Orange circles represent the analysed cluster catalogue. Right panel: Gaia DR3 BP/RP excess factor as … view at source ↗
Figure 2
Figure 2. Left panel: Projected spatial distribution of the M33 cluster sample colour-coded by their radial velocity corrected for the systemic radial velocity of M33. The circular markers reflect those clusters on prograde orbits, orbiting with the stellar disk, whilst the triangle represent those identified as being on retrograde orbits. The clusters lying on the large yellow circles represent the bona fide globular cluster… view at source ↗
Figure 3
Figure 3. Rotational velocity as a function of radius for the cluster population with red circles denoting the prograde population and magenta triangles denoting the retrograde population (see Section 3.1 to see the kinematic distinction between these two population. Those stellar cluster superposed on the larger yellow circles representing the bona fide systems. The blue crosses represent the HII regions with the green band … view at source ↗
Figures from the paper (5 more)
Figure 4
Figure 4. Figure 4: Radial velocities as a function of position angle with respect to the major axis of M33, shown for cluster subsamples in the following radial bins: 𝑅 > 2 kpc, 2 kpc < 𝑅 < 3 kpc, 3 kpc < 𝑅 < 4 kpc, and 𝑅 > 4 kpc. The black lines represent the rotation curve at the corre…
Figure 5
Figure 5. Figure 5: The rotation velocity and velocity dispersion of the cluster popu￾lation in red and the HII regions in blue. The points correspond to the best fit value of the quantities, with the coloured bars denoting 1𝜎 uncertainties in these quantities. The underlying green denote…
Figure 6
Figure 6. Figure 6: The kinetic energy as a function of the vertical component of the angular momentum for the M33 HII regions (blue cross symbols), and the M33 cluster system (solid circles and triangles). As expected, the HII regions traces the prograde motion of the galaxy. Cluster can…
Figure 7
Figure 7. Figure 7: The same as [PITH_FULL_IMAGE:figures/full_fig_p007_7.png]
Figure 8
Figure 8. Figure 8: The age-metallicity relation of the M33 cluster population. The figure also shows the star clusters in the MW (purple), Sgr dwarf spheroidal galaxy (green), the LMC (dark yellow circles), and SMC (light blue). As with the other figures, the magenta triangles indicate r…

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Works this paper leans on

76 extracted references · 32 canonical work pages

  1. [1]

    write newline

    " write newline "" before.all 'output.state := FUNCTION fin.entry write newline FUNCTION new.block output.state before.all = 'skip after.block 'output.state := if FUNCTION new.sentence output.state after.block = 'skip output.state before.all = 'skip after.sentence 'output.state := if if FUNCTION not #0 #1 if FUNCTION and 'skip pop #0 if FUNCTION or pop #1...

  2. [2]

    Alexeeva S., Zhao G., 2022, @doi [ ] 10.3847/1538-4357/ac38ab , https://ui.adsabs.harvard.edu/abs/2022ApJ...925...76A 925, 76

    work page doi:10.3847/1538-4357/ac38ab 2022

  3. [3]

    Anguiano B., 2012, PhD thesis, University of Potsdam, Germany

    work page 2012

  4. [4]

    A., San Roman I., Gallart C., Sarajedini A., Aparicio A., 2015, @doi [ ] 10.1093/mnras/stv943 , https://ui.adsabs.harvard.edu/abs/2015MNRAS.451.3400B 451, 3400

    Beasley M. A., San Roman I., Gallart C., Sarajedini A., Aparicio A., 2015, @doi [ ] 10.1093/mnras/stv943 , https://ui.adsabs.harvard.edu/abs/2015MNRAS.451.3400B 451, 3400

    doi:10.1093/mnras/stv943 2015

  5. [6]

    Bellazzini M., Ibata R., Malhan K., Martin N., Famaey B., Thomas G., 2020b, @doi [ ] 10.1051/0004-6361/202037621 , https://ui.adsabs.harvard.edu/abs/2020A&A...636A.107B 636, A107

    doi:10.1051/0004-6361/202037621

  6. [7]

    Belokurov V., Kravtsov A., 2024, @doi [ ] 10.1093/mnras/stad3920 , https://ui.adsabs.harvard.edu/abs/2024MNRAS.528.3198B 528, 3198

    doi:10.1093/mnras/stad3920 2024

  7. [8]

    P., Tonry J

    Blakeslee J. P., Tonry J. L., Metzger M. R., 1997, @doi [ ] 10.1086/118488 , https://ui.adsabs.harvard.edu/abs/1997AJ....114..482B 114, 482

    doi:10.1086/118488 1997

  8. [9]

    P., Strader J., 2006, @doi [ ] 10.1146/annurev.astro.44.051905.092441 , https://ui.adsabs.harvard.edu/abs/2006ARA&A..44..193B 44, 193

    Brodie J. P., Strader J., 2006, @doi [ ] 10.1146/annurev.astro.44.051905.092441 , https://ui.adsabs.harvard.edu/abs/2006ARA&A..44..193B 44, 193

    arXiv 2006

Show all 76 references
  1. [10]

    A., 2020, @doi [ ] 10.3847/1538-3881/ab5b0e , https://ui.adsabs.harvard.edu/abs/2020AJ....159...56B 159, 56

    Burkert A., Forbes D. A., 2020, @doi [ ] 10.3847/1538-3881/ab5b0e , https://ui.adsabs.harvard.edu/abs/2020AJ....159...56B 159, 56

    2020 doi

  2. [11]

    A., Harding P., 2011, @doi [ ] 10.1088/0004-6256/141/2/61 , https://ui.adsabs.harvard.edu/abs/2011AJ....141...61C 141, 61

    Caldwell N., Schiavon R., Morrison H., Rose J. A., Harding P., 2011, @doi [ ] 10.1088/0004-6256/141/2/61 , https://ui.adsabs.harvard.edu/abs/2011AJ....141...61C 141, 61

    2011 doi

  3. [12]

    C., Sarajedini A., 2002, @doi [ ] 10.1086/324147 , https://ui.adsabs.harvard.edu/abs/2002ApJ...564..712C 564, 712

    Chandar R., Bianchi L., Ford H. C., Sarajedini A., 2002, @doi [ ] 10.1086/324147 , https://ui.adsabs.harvard.edu/abs/2002ApJ...564..712C 564, 712

    2002 doi

  4. [13]

    H., Sarajedini A., Goudfrooij P., 2006, @doi [ ] 10.1086/506984 , https://ui.adsabs.harvard.edu/abs/2006ApJ...646L.107C 646, L107

    Chandar R., Puzia T. H., Sarajedini A., Goudfrooij P., 2006, @doi [ ] 10.1086/506984 , https://ui.adsabs.harvard.edu/abs/2006ApJ...646L.107C 646, L107

    2006 doi

  5. [14]

    C., et al., 2013, @doi [ ] 10.1093/mnras/sts392 , https://ui.adsabs.harvard.edu/abs/2013MNRAS.430...37C 430, 37

    Chapman S. C., et al., 2013, @doi [ ] 10.1093/mnras/sts392 , https://ui.adsabs.harvard.edu/abs/2013MNRAS.430...37C 430, 37

    2013 doi

  6. [15]

    A., Schommer R

    Christian C. A., Schommer R. A., 1982, @doi [ ] 10.1086/190804 , https://ui.adsabs.harvard.edu/abs/1982ApJS...49..405C 49, 405

    1982 doi

  7. [16]

    Cockcroft R., et al., 2011, @doi [ ] 10.1088/0004-637X/730/2/112 , https://ui.adsabs.harvard.edu/abs/2011ApJ...730..112C 730, 112

    2011 doi

  8. [17]

    Collins M. L. M., et al., 2024, @doi [ ] 10.1093/mnras/stae199 , https://ui.adsabs.harvard.edu/abs/2024MNRAS.528.2614C 528, 2614

    2024 doi

  9. [18]

    Corbelli E., Salucci P., 2000, @doi [ ] 10.1046/j.1365-8711.2000.03075.x , https://ui.adsabs.harvard.edu/abs/2000MNRAS.311..441C 311, 441

    2000

  10. [19]

    E., 1997, @doi [ ] 10.1086/303849 , https://ui.adsabs.harvard.edu/abs/1997ApJ...479..244C 479, 244

    Corbelli E., Schneider S. E., 1997, @doi [ ] 10.1086/303849 , https://ui.adsabs.harvard.edu/abs/1997ApJ...479..244C 479, 244

    1997 doi

  11. [20]

    Corbelli E., Walterbos R. A. M., 2007, @doi [ ] 10.1086/521618 , https://ui.adsabs.harvard.edu/abs/2007ApJ...669..315C 669, 315

    2007 doi

  12. [21]

    Corbelli E., Thilker D., Zibetti S., Giovanardi C., Salucci P., 2014, @doi [ ] 10.1051/0004-6361/201424033 , https://ui.adsabs.harvard.edu/abs/2014A&A...572A..23C 572, A23

    2014 doi

  13. [22]

    R., et al., 2023, @doi [ ] 10.3847/1538-4357/ad003b , https://ui.adsabs.harvard.edu/abs/2023ApJ...958..157C 958, 157

    Cullinane L. R., et al., 2023, @doi [ ] 10.3847/1538-4357/ad003b , https://ui.adsabs.harvard.edu/abs/2023ApJ...958..157C 958, 157

    2023 doi

  14. [23]

    Drlica-Wagner A., et al., 2015, @doi [ ] 10.1088/0004-637X/813/2/109 , https://ui.adsabs.harvard.edu/abs/2015ApJ...813..109D 813, 109

    2015 doi

  15. [24]

    Ferguson A., Irwin2 M., Chapman S., Ibata R., Lewis G., Tanvir N., 2007, in Island Universes. p. 239 ( @eprint arXiv astro-ph/0601121 ), @doi 10.1007/978-1-4020-5573-7_39

    2007 arXiv

  16. [26]

    M., et al., 2022, @doi [ ] 10.3847/1538-4357/ac3480 , https://ui.adsabs.harvard.edu/abs/2022ApJ...924..116G 924, 116

    Gilbert K. M., et al., 2022, @doi [ ] 10.3847/1538-4357/ac3480 , https://ui.adsabs.harvard.edu/abs/2022ApJ...924..116G 924, 116

    2022 doi

  17. [27]

    Golubov O., et al., 2013, @doi [ ] 10.1051/0004-6361/201321559 , https://ui.adsabs.harvard.edu/abs/2013A&A...557A..92G 557, A92

    2013 doi

  18. [28]

    Grossi M., Hwang N., Corbelli E., Giovanardi C., Okamoto S., Arimoto N., 2011, @doi [ ] 10.1051/0004-6361/201117019 , https://ui.adsabs.harvard.edu/abs/2011A&A...533A..91G 533, A91

    2011 doi

  19. [29]

    F., et al., 2023, @doi [ ] 10.1093/mnras/stad1902 , https://ui.adsabs.harvard.edu/abs/2023MNRAS.525.2241H 525, 2241

    Hopkins P. F., et al., 2023, @doi [ ] 10.1093/mnras/stad1902 , https://ui.adsabs.harvard.edu/abs/2023MNRAS.525.2241H 525, 2241

    2023 doi

  20. [30]

    E., Pfeffer J

    Horta D., Hughes M. E., Pfeffer J. L., Bastian N., Kruijssen J. M. D., Reina-Campos M., Crain R. A., 2021, @doi [ ] 10.1093/mnras/staa3522 , https://ui.adsabs.harvard.edu/abs/2021MNRAS.500.4768H 500, 4768

    2021 doi

  21. [31]

    K., et al., 2021, @doi [ ] 10.3847/1538-4357/abf63c , https://ui.adsabs.harvard.edu/abs/2021ApJ...914...16H 914, 16

    Hughes A. K., et al., 2021, @doi [ ] 10.3847/1538-4357/abf63c , https://ui.adsabs.harvard.edu/abs/2021ApJ...914...16H 914, 16

    2021 doi

  22. [32]

    Huxor A., Ferguson A. M. N., Barker M. K., Tanvir N. R., Irwin M. J., Chapman S. C., Ibata R., Lewis G., 2009, @doi [ ] 10.1088/0004-637X/698/2/L77 , https://ui.adsabs.harvard.edu/abs/2009ApJ...698L..77H 698, L77

    2009 doi

  23. [33]

    P., et al., 2011, @doi [ ] 10.1111/j.1365-2966.2011.18450.x , https://ui.adsabs.harvard.edu/abs/2011MNRAS.414..770H 414, 770

    Huxor A. P., et al., 2011, @doi [ ] 10.1111/j.1365-2966.2011.18450.x , https://ui.adsabs.harvard.edu/abs/2011MNRAS.414..770H 414, 770

    2011

  24. [34]

    Jethwa P., Erkal D., Belokurov V., 2016, @doi [ ] 10.1093/mnras/stw1343 , https://ui.adsabs.harvard.edu/abs/2016MNRAS.461.2212J 461, 2212

    2016 doi

  25. [35]

    W., et al., 2018, @doi [ ] 10.1093/mnras/sty1674 , https://ui.adsabs.harvard.edu/abs/2018MNRAS.479.2505K 479, 2505

    Koch E. W., et al., 2018, @doi [ ] 10.1093/mnras/sty1674 , https://ui.adsabs.harvard.edu/abs/2018MNRAS.479.2505K 479, 2505

    2018 doi

  26. [36]

    Kruijssen J. M. D., Pfeffer J. L., Crain R. A., Bastian N., 2019a, @doi [ ] 10.1093/mnras/stz968 , https://ui.adsabs.harvard.edu/abs/2019MNRAS.486.3134K 486, 3134

    doi

  27. [37]

    Kruijssen J. M. D., Pfeffer J. L., Reina-Campos M., Crain R. A., Bastian N., 2019b, @doi [ ] 10.1093/mnras/sty1609 , https://ui.adsabs.harvard.edu/abs/2019MNRAS.486.3180K 486, 3180

    doi

  28. [38]

    S., Brodie J

    Larsen S. S., Brodie J. P., Wasserman A., Strader J., 2018, @doi [ ] 10.1051/0004-6361/201731909 , https://ui.adsabs.harvard.edu/abs/2018A&A...613A..56L 613, A56

    2018 doi

  29. [39]

    S., Eitner P., Magg E., Bergemann M., Moltzer C

    Larsen S. S., Eitner P., Magg E., Bergemann M., Moltzer C. A. S., Brodie J. P., Romanowsky A. J., Strader J., 2022, @doi [ ] 10.1051/0004-6361/202142243 , https://ui.adsabs.harvard.edu/abs/2022A&A...660A..88L 660, A88

    2022 doi

  30. [40]

    R., Majewski S

    Law D. R., Majewski S. R., 2010, @doi [ ] 10.1088/0004-637X/718/2/1128 , https://ui.adsabs.harvard.edu/abs/2010ApJ...718.1128L 718, 1128

    2010 doi

  31. [41]

    O., P \'e rez-Villegas A., Rossi S., Perottoni H

    Limberg G., Souza S. O., P \'e rez-Villegas A., Rossi S., Perottoni H. D., Santucci R. M., 2022, arXiv e-prints, https://ui.adsabs.harvard.edu/abs/2022arXiv220610505L p. arXiv:2206.10505

    2022 arXiv

  32. [42]

    J., Brunthaler A., Falcke H., 2005, @doi [ ] 10.1086/491644 , https://ui.adsabs.harvard.edu/abs/2005ApJ...633..894L 633, 894

    Loeb A., Reid M. J., Brunthaler A., Falcke H., 2005, @doi [ ] 10.1086/491644 , https://ui.adsabs.harvard.edu/abs/2005ApJ...633..894L 633, 894

    2005 doi

  33. [43]

    D., et al., 2010, @doi [ ] 10.1088/2041-8205/717/1/L11 , https://ui.adsabs.harvard.edu/abs/2010ApJ...717L..11M 717, L11

    Mackey A. D., et al., 2010, @doi [ ] 10.1088/2041-8205/717/1/L11 , https://ui.adsabs.harvard.edu/abs/2010ApJ...717L..11M 717, L11

    2010 doi

  34. [44]

    Mar \' n-Franch A., et al., 2009, @doi [ ] 10.1088/0004-637X/694/2/1498 , https://ui.adsabs.harvard.edu/abs/2009ApJ...694.1498M 694, 1498

    2009 doi

  35. [45]

    H., Helmi A., 2019, @doi [ ] 10.1051/0004-6361/201936135 , https://ui.adsabs.harvard.edu/abs/2019A&A...630L...4M 630, L4

    Massari D., Koppelman H. H., Helmi A., 2019, @doi [ ] 10.1051/0004-6361/201936135 , https://ui.adsabs.harvard.edu/abs/2019A&A...630L...4M 630, L4

    2019 doi

  36. [46]

    W., Chapman S

    McConnachie A. W., Chapman S. C., Ibata R. A., Ferguson A. M. N., Irwin M. J., Lewis G. F., Tanvir N. R., Martin N., 2006, @doi [ ] 10.1086/507299 , https://ui.adsabs.harvard.edu/abs/2006ApJ...647L..25M 647, L25

    2006 doi

  37. [48]

    W., et al., 2009b, @doi [ ] 10.1038/nature08327 , https://ui.adsabs.harvard.edu/abs/2009Natur.461...66M 461, 66

    McConnachie A. W., et al., 2009b, @doi [ ] 10.1038/nature08327 , https://ui.adsabs.harvard.edu/abs/2009Natur.461...66M 461, 66

    doi

  38. [49]

    W., Ferguson A

    McConnachie A. W., Ferguson A. M. N., Irwin M. J., Dubinski J., Widrow L. M., Dotter A., Ibata R., Lewis G. F., 2010, @doi [ ] 10.1088/0004-637X/723/2/1038 , https://ui.adsabs.harvard.edu/abs/2010ApJ...723.1038M 723, 1038

    2010 doi

  39. [50]

    W., et al., 2018, @doi [ ] 10.3847/1538-4357/aae8e7 , https://ui.adsabs.harvard.edu/abs/2018ApJ...868...55M 868, 55

    McConnachie A. W., et al., 2018, @doi [ ] 10.3847/1538-4357/aae8e7 , https://ui.adsabs.harvard.edu/abs/2018ApJ...868...55M 868, 55

    2018 doi

  40. [51]

    McMonigal B., et al., 2016, @doi [ ] 10.1093/mnras/stw1657 , https://ui.adsabs.harvard.edu/abs/2016MNRAS.461.4374M 461, 4374

    2016 doi

  41. [52]

    F., Frenk C

    Navarro J. F., Frenk C. S., White S. D. M., 1996, @doi [ ] 10.1086/177173 , https://ui.adsabs.harvard.edu/abs/1996ApJ...462..563N 462, 563

    1996 doi

  42. [53]

    arXiv:2403.14234

    Ogami I., et al., 2024, @doi [arXiv e-prints] 10.48550/arXiv.2403.14234 , https://ui.adsabs.harvard.edu/abs/2024arXiv240314234O p. arXiv:2403.14234

    2024 doi arXiv

  43. [54]

    L., Tollerud E

    Patel E., Carlin J. L., Tollerud E. J., Collins M. L. M., Dooley G. A., 2018, @doi [ ] 10.1093/mnras/sty1946 , https://ui.adsabs.harvard.edu/abs/2018MNRAS.480.1883P 480, 1883

    2018 doi

  44. [55]

    L., Trujillo-Gomez S., Kruijssen J

    Pfeffer J. L., Trujillo-Gomez S., Kruijssen J. M. D., Crain R. A., Hughes M. E., Reina-Campos M., Bastian N., 2020, @doi [ ] 10.1093/mnras/staa3109 , https://ui.adsabs.harvard.edu/abs/2020MNRAS.499.4863P 499, 4863

    2020 doi

  45. [56]

    E., et al., 2009, @doi [ ] 10.1088/0004-637X/703/2/1486 , https://ui.adsabs.harvard.edu/abs/2009ApJ...703.1486P 703, 1486

    Putman M. E., et al., 2009, @doi [ ] 10.1088/0004-637X/703/2/1486 , https://ui.adsabs.harvard.edu/abs/2009ApJ...703.1486P 703, 1486

    2009 doi

  46. [57]

    W., Paltoglou G., 1984, @doi [ ] 10.1086/184320 , https://ui.adsabs.harvard.edu/abs/1984ApJ...283L...5R 283, L5

    Rodgers A. W., Paltoglou G., 1984, @doi [ ] 10.1086/184320 , https://ui.adsabs.harvard.edu/abs/1984ApJ...283L...5R 283, L5

    1984 doi

  47. [58]

    H., Wright M

    Rogstad D. H., Wright M. C. H., Lockhart I. A., 1976, @doi [ ] 10.1086/154219 , https://ui.adsabs.harvard.edu/abs/1976ApJ...204..703R 204, 703

    1976 doi

  48. [59]

    C., Ford W

    Rubin V. C., Ford W. Kent J., 1970, @doi [ ] 10.1086/150317 , https://ui.adsabs.harvard.edu/abs/1970ApJ...159..379R 159, 379

    1970 doi

  49. [60]

    San Roman I., Sarajedini A., Aparicio A., 2010, @doi [ ] 10.1088/0004-637X/720/2/1674 , https://ui.adsabs.harvard.edu/abs/2010ApJ...720.1674S 720, 1674

    2010 doi

  50. [61]

    L., 2007, @doi [ ] 10.1086/518835 , https://ui.adsabs.harvard.edu/abs/2007AJ....134..447S 134, 447

    Sarajedini A., Mancone C. L., 2007, @doi [ ] 10.1086/518835 , https://ui.adsabs.harvard.edu/abs/2007AJ....134..447S 134, 447

    2007 doi

  51. [62]

    Sarajedini A., Geisler D., Harding P., Schommer R., 1998, @doi [ ] 10.1086/311707 , https://ui.adsabs.harvard.edu/abs/1998ApJ...508L..37S 508, L37

    1998 doi

  52. [63]

    Sarajedini A., Geisler D., Schommer R., Harding P., 2000, @doi [ ] 10.1086/316807 , https://ui.adsabs.harvard.edu/abs/2000AJ....120.2437S 120, 2437

    2000 doi

  53. [64]

    A., Christian C

    Schommer R. A., Christian C. A., Caldwell N., Bothun G. D., Huchra J., 1991, @doi [ ] 10.1086/115732 , https://ui.adsabs.harvard.edu/abs/1991AJ....101..873S 101, 873

    1991 doi

  54. [65]

    Searle L., Zinn R., 1978, @doi [ ] 10.1086/156499 , https://ui.adsabs.harvard.edu/abs/1978ApJ...225..357S 225, 357

    1978 doi

  55. [66]

    E., Chandar R., Puzia T

    Sharina M. E., Chandar R., Puzia T. H., Goudfrooij P., Davoust E., 2010, @doi [ ] 10.1111/j.1365-2966.2010.16510.x , https://ui.adsabs.harvard.edu/abs/2010MNRAS.405..839S 405, 839

    2010

  56. [67]

    R., Forbes D

    Spitler L. R., Forbes D. A., 2009, @doi [ ] 10.1111/j.1745-3933.2008.00567.x , https://ui.adsabs.harvard.edu/abs/2009MNRAS.392L...1S 392, L1

    2009

  57. [68]

    S., White S

    Springel V., Frenk C. S., White S. D. M., 2006, @doi [ ] 10.1038/nature04805 , http://adsabs.harvard.edu/abs/2006Natur.440.1137S 440, 1137

    2006 doi

  58. [69]

    M., Remus R.-S., McKenzie M., Forbes D

    Valenzuela L. M., Remus R.-S., McKenzie M., Forbes D. A., 2023, @doi [arXiv e-prints] 10.48550/arXiv.2309.11545 , https://ui.adsabs.harvard.edu/abs/2023arXiv230911545V p. arXiv:2309.11545

    2023 doi arXiv

  59. [70]

    Veljanoski J., et al., 2014, @doi [ ] 10.1093/mnras/stu1055 , https://ui.adsabs.harvard.edu/abs/2014MNRAS.442.2929V 442, 2929

    2014 doi

  60. [71]

    Wang Y., Yuan H., Chen B., Chen X., Wu H., Niu Z., Huang S., Liu J., 2023, @doi [ ] 10.3847/1538-4357/ace963 , https://ui.adsabs.harvard.edu/abs/2023ApJ...954..206W 954, 206

    2023 doi

  61. [72]

    Wenger M., et al., 2000, @doi [ ] 10.1051/aas:2000332 , https://ui.adsabs.harvard.edu/abs/2000A&AS..143....9W 143, 9

    2000 doi

  62. [73]

    C., 2021, @doi [ ] 10.3847/1538-3881/abff5f , https://ui.adsabs.harvard.edu/abs/2021AJ....162...42W 162, 42

    Woody T., Schlaufman K. C., 2021, @doi [ ] 10.3847/1538-3881/abff5f , https://ui.adsabs.harvard.edu/abs/2021AJ....162...42W 162, 42

    2021 doi

  63. [74]

    H., 2017, @doi [arXiv e-prints] 10.48550/arXiv.1706.04248 , https://ui.adsabs.harvard.edu/abs/2017arXiv170604248Z p

    Zacharie Kam S., Carignan C., Chemin L., Foster T., Elson E., Jarrett T. H., 2017, @doi [arXiv e-prints] 10.48550/arXiv.1706.04248 , https://ui.adsabs.harvard.edu/abs/2017arXiv170604248Z p. arXiv:1706.04248

    2017 doi arXiv

  64. [75]

    H., Brodie J

    Zinn R., 1993, in Smith G. H., Brodie J. P., eds, Astronomical Society of the Pacific Conference Series Vol. 48, The Globular Cluster-Galaxy Connection. p. 38

    1993

  65. [76]

    de Meulenaer P., Narbutis D., Mineikis T., Vansevi c ius V., 2015, @doi [ ] 10.1051/0004-6361/201526544 , https://ui.adsabs.harvard.edu/abs/2015A&A...581A.111D 581, A111

    2015 doi

  66. [77]

    van den Bergh S., 2000, @doi [ ] 10.1086/316548 , https://ui.adsabs.harvard.edu/abs/2000PASP..112..529V 112, 529

    2000 doi

  67. [78]

    P., Fardal M

    van der Marel R. P., Fardal M. A., Sohn S. T., Patel E., Besla G., del Pino A., Sahlmann J., Watkins L. L., 2019, @doi [ ] 10.3847/1538-4357/ab001b , https://ui.adsabs.harvard.edu/abs/2019ApJ...872...24V 872, 24

    2019 doi

  68. [79]

    write newline

    " write newline "" before.all 'output.state := FUNCTION fin.entry write newline FUNCTION new.block output.state before.all = 'skip after.block 'output.state := if FUNCTION new.sentence output.state after.block = 'skip output.state before.all = 'skip after.sentence 'output.stat...

Pith tools

Reviewed August 6, 2026 · model on record in the stance chip above.