Looking into the faintEst WIth MUSE (LEWIS): Exploring the nature of ultra-diffuse galaxies in the Hydra I cluster III. Untangling UDG 32 from the stripped filaments of NGC 3314A with multi-wavelength data

B. Poggianti; C. Buttitta; C. C. de la Casa; C. Spiniello; D. A. Forbes; E. Iodice; E. M. Corsini; G. D'Ago; G. Doll; J. Falc\'on-Barroso

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Looking into the faintEst WIth MUSE (LEWIS): Exploring the nature of ultra-diffuse galaxies in the Hydra I cluster III. Untangling UDG 32 from the stripped filaments of NGC 3314A with multi-wavelength data

T0 review · 2 major / 5 minor · reviewed 2026-08-10 · deepseek-v4-flash

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Pith's one-line read UDG 32, an ultra-diffuse galaxy lying inside the stripped filaments of the jellyfish galaxy NGC 3314A, is an intermediate-age, metal-rich galaxy belonging to the Hydra I south-east subgroup rather than a young clump formed from the…

desk verdict A careful, honest single-object study that delivers genuinely new measurements, but its central age/metallicity conclusion rests on a four-band SED fit with one parametric SFH, so treat that part as provisional. read the letter →

arxiv 2501.16192 v1 pith:AFUB53VI submitted 2025-01-27 astro-ph.GA

J. Hartke , E. Iodice , M. Gullieuszik , M. Mirabile , C. Buttitta , G. Doll , G. D'Ago , C. C. de la Casa

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K. M. Hess R. Kotulla B. Poggianti M. Arnaboldi M. Cantiello E. M. Corsini J. Falcón-Barroso D. A. Forbes M. Hilker S. Mieske M. Rejkuba M. Spavone C. Spiniello

This is my paper · ORCID

classification astro-ph.GA

keywords ultra-diffusegalaxiesHydraIclusterNGC3314Aram-pressurestrippingjellyfishintegral-fieldspectroscopystellarpopulationsglobularclusters

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 tests a specific idea: whether UDG 32, an ultra-diffuse galaxy discovered inside the stellar filaments of the jellyfish galaxy NGC 3314A, formed from gas ram-pressure stripped off NGC 3314A. Using new MUSE integral-field spectroscopy, the authors show that the stripped material, traced by H$\alpha$ and other emission lines, extends more than three arcminutes from NGC 3314A and fully overlaps UDG 32 in projection, with eleven star-forming knots consistent with ram-pressure-triggered star formation. The line-of-sight velocity of UDG 32, $v_{\rm LOS}=3080\pm 120$ km/s, places it in the same kinematic structure as NGC 3314A and the Hydra I cluster's south-east subgroup. Fitting the DECam photometry gives a mass-weighted age of $7.7^{+2.9}_{-2.8}$ Gyr and a near-solar metallicity of $[M/H] = 0.07^{+0.19}_{-0.32}$, which is too old for a galaxy born from the currently visible tail. The paper concludes that UDG 32 formed from pre-enriched material stripped from a more massive galaxy in the south-east group, while leaving open whether that material came from NGC 3314A itself.

What carries the argument

The argument is carried by pairing kinematics from integral-field spectroscopy with stellar-population information from SED fitting. The MUSE data are fitted with pPXF using the E-MILES stellar library to measure the line-of-sight velocity of UDG 32, the velocities of the two globular clusters, and the kinematics of the star-forming knots in the stripped tail. The stripped material is mapped with a continuum-subtracted H$\alpha$ narrow-band image built from the MUSE cube, and the knots are classified on a Baldwin-Phillips-Terlevich emission-line ratio diagram using the Kewley et al. (2001) demarcation curve. The stellar population parameters come from fitting the DECam $ugri$ photometry with Bagpipes, which uses Bruzual & Charlot (2003) stellar population models, a Kroupa initial mass function, an exponentially declining star-formation history, and Calzetti dust attenuation. The GALEX ultraviolet photometry is not included in the final fit, because none of the best-fit models can reproduce the large UV fluxes and the light cannot be spatially separated from the filament; the fit therefore covers four optical bands only. The discriminating quantity is age: a UDG born from the currently visible RPS tail would be a fraction of a gigayear old, whereas UDG 32's best-fit age is roughly $8$ Gyr.

What would settle it

Take deep optical spectra of the stellar body of UDG 32 in regions not covered by the H$\alpha$ filament, reaching a signal-to-noise ratio of at least 15, and measure Balmer and metal absorption lines directly; if the absorption-line age is younger than about one gigayear, or the metallicity is clearly subsolar, the claim that UDG 32 formed from pre-enriched, stripped material is refuted.

Watch

Extended reading notes

Core claim

UDG 32 is not a young object condensed from the presently visible stripped tail of NGC 3314A. The central discovery is that UDG 32 is an intermediate-age ($7.7^{+2.9}_{-2.8}$ Gyr), near-solar-metallicity ($[M/H] = 0.07^{+0.19}_{-0.32}$) ultra-diffuse galaxy belonging to the Hydra I cluster south-east subgroup, with a line-of-sight velocity of $v_{\rm LOS}=3080\pm 120$ km/s (or $3085\pm 38$ km/s from a shorter spectral window around H$\alpha$). The MUSE cube reveals the stripped material of NGC 3314A, traced by H$\alpha$, H$\beta$, and forbidden lines, extending more than three arcminutes from the parent galaxy and completely overlapping UDG 32 in projection; eleven of twelve detected knots are classified as star-forming, consistent with ram-pressure-triggered star formation. Still, the galaxy's old, metal-rich population is incompatible with formation from a stripped gas clump in the current tail, which would be only a fraction of a gigayear old. The paper concludes that UDG 32 formed from pre-enriched material in the south-east group, liberated from a more massive galaxy by tidal or ram-pressure stripping, while explicitly stating that a direct association with NGC 3314A's stripped material cannot be established. The two globular clusters confirmed in the field, with velocities $3594\pm 23$ and $3905\pm 26$ km/s, are kinematically not bound to UDG 32 and belong to the Hydra I intracluster globular cluster population.

Load-bearing premise

The load-bearing assumption is that the age and metal content derived from fitting four optical bands with a single smooth star-formation history are correct, and that the extra ultraviolet light around the galaxy comes from NGC 3314A's stripped gas rather than from UDG 32 itself; if either is wrong, UDG 32 could be younger and poorer in metals, and the proposed formation scenario would not follow.

Editorial extensions

If this is right

UDG 32 is now placed kinematically in the Hydra I south-east subgroup, so it should be treated as an older, chemically enriched member of that group rather than as a young galaxy forming inside the visible tail.
The stripped medium of NGC 3314A extends beyond three arcminutes from the parent galaxy and hosts at least eleven star-forming knots, showing that ram-pressure-triggered star formation can occur at large projected distances.
The two globular clusters in the MUSE field are added to the Hydra I intracluster globular cluster population, and the lack of GCs bound to UDG 32 is consistent with a formation from stripped material rather than from tidal heating of a normal dwarf galaxy.
A future velocity-dispersion measurement can discriminate between the remaining scenarios: a low mass-to-light ratio would favour a dark-matter-poor origin from stripped material, while dwarf-like dark matter content would favour tidal heating.

Reading between the lines

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

If other low-surface-brightness galaxies found inside jellyfish tails are re-examined with the same tools, many may turn out to be older galaxies projected onto the tails rather than new dwarfs born there; age and metallicity would be the decisive tests.
The GALEX ultraviolet excess that the models cannot reproduce is a concrete next target: spatially resolved UV imaging with sub-arcsecond resolution would settle whether any young stars exist inside UDG 32, and a young component would weaken the pre-enriched-material interpretation.
A near-solar metallicity at a stellar mass of a few times $10^7\,M_\odot$ would place UDG 32 well above the dwarf galaxy mass-metallicity relation; confirming this with absorption-line spectroscopy would strengthen the case that its stars were enriched inside a more massive progenitor before being stripped.

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Editorial analysis

A structured set of objections, weighed in public.

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

Desk Editor's Note

read the letter

You should know three things about this paper. First, it is a genuinely useful observational step: first line-of-sight velocity for UDG 32, first SED-based stellar population estimates, H-alpha emission from NGC 3314A's stripped tail extending past UDG 32, and two spectroscopically confirmed intracluster globular clusters. Second, the data handling is unusually careful. They noticed that the standard reduction misinterprets redshifted H-alpha as sky lines, built masks to avoid it, ran a pre-ZAP consistency check on the velocity, and disclose the UV-fitting problem rather than hiding it. Third, the main interpretation is softer than the abstract suggests: the claim that UDG 32 is an intermediate-age, near-solar-metallicity object formed from pre-enriched material depends on a Bagpipes fit to only four DECam bands (ugri) with a single exponentially declining SFH and a Calzetti dust law. The GALEX UV points are excluded because the best-fit models cannot reproduce them, and the paper admits the UV could be filament light. That is the load-bearing pillar of the formation-scenario argument.

What the paper does well: it separates UDG 32 from the filament kinematically and morphologically, and the velocity (3080±120 km/s, with a tighter H-alpha-region fit of 3085±38 km/s) robustly places it in the Hydra I south-east subgroup. The globular cluster velocities are clean and clearly place those objects in the intracluster population. The BPT classification of the star-forming knots and the abundance work are solid. The comparison table of formation scenarios is honest about what is and is not constrained.

Soft spots, in proportion. The SED fit is the main one. With four optical points, age-dust-SFH degeneracies are real, and a flexible SFH (e.g., old base plus recent burst) could shift the mass-weighted age down. The paper shows overlapping posteriors when UV is included, but that tests the UV exclusion, not the SFH family. This is a model-dependence concern, not an internal inconsistency, but it means the 'not young' conclusion is not ironclad. The low-SNR velocity is a secondary concern, but they handle it conservatively. The link to pre-enriched material from a specific more massive galaxy is speculative, as they themselves say. Minor point: the abstract says 'confirmed that UDG 32 is part of the same kinematic structure as NGC 3314A' but the velocity difference is a few hundred km/s; the association rests on broader group membership, which is fine but worth noting.

Who is this for? Anyone working on UDG formation, jellyfish galaxies, or the Hydra I cluster. It is a solid single-object contribution, not a paradigm shift. It deserves a serious referee: send it to review, and ask the authors to run a flexible-SFH test or explicitly justify why the single tau model is sufficient. That would harden the central claim.

Referee Report

2 major / 5 minor

Summary. This paper uses new MUSE integral-field spectroscopy and deep multi-band photometry to investigate the nature of UDG 32, an ultra-diffuse galaxy candidate projected onto the stripped filaments of the jellyfish galaxy NGC 3314A in the Hydra I cluster. The authors detect extended Hα and other emission lines from the stripped material, trace it beyond UDG 32 in projection, and identify star-forming knots in the filament. They measure the line-of-sight velocity of UDG 32 (v_LOS = 3080 ± 120 km/s) from a low-SNR spectrum with bootstrapped errors and a pre-ZAP consistency check, and they confirm two globular clusters whose velocities place them in the Hydra I intracluster population. SED fitting with Bagpipes on four DECam bands yields a mass-weighted age of 7.7^{+2.9}_{-2.8} Gyr, [M/H] = 0.07^{+0.19}_{-0.32}, and M* = 6.7^{+2.0}_{-1.8} x 10^7 M_sun; the GALEX UV points are excluded because the best-fit models cannot reproduce them and the UV may be contaminated by the filament. The paper concludes that UDG 32 belongs to the Hydra I south-east subgroup and that its intermediate-age, metal-rich stellar population favors formation from pre-enriched material liberated from a more massive galaxy, while a direct link to the currently visible ram-pressure-stripped tail of NGC 3314A cannot be established.

Significance. If the stellar population result is robust, UDG 32 would be one of the first UDGs with evidence for formation from pre-enriched, stripped material, and the paper would strengthen the emerging picture that UDG formation channels are environmentally diverse. The kinematic and morphological results are solid and provide a clear separation between the galaxy and the foreground filament, and the confirmation of two intracluster GCs is a useful contribution. The paper is also methodologically careful: it describes an improved data-reduction workflow that avoids sky-subtraction artifacts from the bright emission-line filament, validates the velocity measurement against a pre-ZAP reduction, and explicitly reports systematic uncertainties. These strengths make the paper a valuable addition to the LEWIS series even though the SED-based age and metallicity rest on limited photometric leverage.

major comments (2)

[Sect. 5 and Appendix F] The mass-weighted age and metallicity that drive the interpretation in Sect. 6 are derived from only four DECam optical bands with a single exponentially declining SFH and a Calzetti dust law, after excluding the GALEX UV points because the best-fit models cannot reproduce them. The UV data are the most sensitive to a young stellar component, and the excluded points are only re-added as an additional fit in Table F.1, which does not test the SFH family. Please demonstrate with at least one alternative SFH parameterization (e.g., a two-component old-plus-burst model or a non-parametric SFH) that the posterior does not allow a significant mass fraction at ages below ~1-2 Gyr; without this test, the argument against a young RPS-clump origin for UDG 32 is not fully supported.
[Appendix B / Sect. 5] The 18.71-arcsec aperture used for the DECam photometry covers a substantial fraction of the Hα filament, including the star-forming knots identified in Sect. 3. Although the two GCs and other sources are masked, the residual contribution of the filament's stellar continuum and of unmasked HII knots to the ugri fluxes is not quantified. If this contamination is non-negligible, the fitted age and metallicity would be biased. Please estimate an upper limit on this contamination (e.g., by comparing the surface brightness of the filament outside UDG 32) or state explicitly why it is negligible.

minor comments (5)

[Sect. 4.1] The paper reports two LOS velocities (3080±120 km/s and 3085±38 km/s); please state explicitly which measurement is used in Fig. 3 and as the redshift prior in the SED fit.
[Fig. 1] The orange aperture circle is difficult to see in the printed version; consider increasing its line width or using a different color.
[Sect. 3] There is a typo in the sentence beginning 'The SNRs of the fitted lines range from∼ 2 to∼ 50' where 'range' should be 'ranges'.
[Appendix A] The choice of the central 1/3 Reff of the UDG as part of the sky mask is unusual and could affect the continuum shape of the extracted spectrum; a one-sentence justification would be helpful.
[Sect. 4.1] The paper uses the term 'foreground filament' although the relative line-of-sight position of the filament and UDG 32 is not determined; consider using 'projected filament' to avoid ambiguity.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the conclusions are empirical inferences from independent MUSE kinematics and multi-band SED fitting, with acknowledged model caveats rather than definitional reductions.

full rationale

The paper makes two load-bearing inferences: (1) UDG 32 belongs to the Hydra I south-east kinematic structure, and (2) its intermediate age and near-solar metallicity disfavour formation from the currently visible RPS clumps. Both are empirical measurements, not derivations from the conclusions. The LOS velocity (vLOS = 3080 +/- 120 km/s) is obtained by pPXF fits to MUSE absorption spectra, and the stellar population parameters are posterior estimates from Bagpipes fits to DECam ugri photometry (with GALEX UV included only as a robustness check). The age and metallicity are not defined in terms of the formation scenario; they are fitted quantities with reported uncertainties and a model-dependent SFH/dust assumption that the authors explicitly discuss. The paper is honest about limitations: the GALEX UV fluxes cannot be reproduced by any best-fit model and may be contaminated by the filament, the MUSE SNR is too low for absorption-line stellar population analysis, and the authors state they cannot establish a direct link to NGC 3314A's stripped material. Self-citations to Iodice et al. (2021, 2023) and Buttitta et al. (2025) provide discovery context and reduction/analysis methods; they do not substitute for the new MUSE data or the external template libraries (E-MILES, Bruzual & Charlot 2003). There is no uniqueness theorem, no fitted input relabeled as a prediction, and no ansatz imported solely through self-citation. Model dependence (single exponential SFH, Calzetti dust, four optical bands) is a robustness concern, not circularity.

Assumptions & free parameters 6 free parameters · 5 assumptions · 0 invented entities

The paper introduces no new particles, forces, or physical entities. Its central claims rest on standard model assumptions: cluster membership via velocity, a specific SPS/IMF/dust framework, low-SNR template fitting, and a parametric SFH used in the Bagpipes fit. The free parameters are the SED-fitting parameters plus the fitted redshift; all are data-fitting parameters rather than invented physics.

free parameters (6)

Stellar mass M* = 6.7 (+2.0/-1.8) x 10^7 Msun
Bagpipes SED fit; depends on the assumed IMF, star-formation history, and dust law.
Mass-weighted age = 7.7 (+2.9/-2.8) Gyr
Primary result from the optical SED fit; drives the formation-scenario conclusion.
Metallicity [M/H] = 0.07 (+0.19/-0.32) dex
Near-solar value supports a pre-enriched origin; degenerates with age and dust in SED fitting.
Dust extinction AV = 0.17 (+0.26/-0.13) mag
Fitted with the Calzetti dust law; correlated with age and metallicity in the SED fit.
Star-formation history e-folding timescale tau = not tabulated
Bagpipes exponentially declining SFH parameter; marginalized over in the posterior, but affects the derived mass-weighted age.
Redshift z = 0.01014 (+0.00061/-0.00069)
Fitted with a prior derived from the MUSE velocity; converts photometry to rest frame and physical scales.

assumptions (5)

domain assumption UDG 32 lies at approximately the Hydra I cluster distance (51 +/- 6 Mpc), with NGC 3314A's distance (~37.3 Mpc) considered as an alternative for sizes.
Adopted to convert angular sizes and magnitudes into physical radii, stellar masses, and rest-frame SED quantities; the velocity association supports cluster membership but no direct distance was measured (Sect. 4.1).
domain assumption Bruzual & Charlot (2003) stellar population synthesis models, a Kroupa & Boily IMF, and the Calzetti dust attenuation law describe UDG 32's stellar populations.
Bagpipes SED fitting (Appendix F) uses these models by construction; different SPS models or IMF choices would shift the derived age and metallicity.
domain assumption E-MILES stellar templates are adequate to recover vLOS from a SNR ~ 3 spectrum with pPXF.
The velocity measurement in Sect. 4.1 and Appendix D assumes no strong template mismatch at very low signal-to-noise; the authors mitigate this with bootstrapping and a pre-ZAP consistency check.
domain assumption The exponentially declining star-formation history with uniform priors is an adequate description of UDG 32's past star formation.
Bagpipes uses this parametric SFH; a different SFH, for example a recent burst hidden by dust, could change the mass-weighted age used in the formation-scenario comparison.
ad hoc to paper The optical aperture photometry is not significantly contaminated by the foreground filament or the masked globular clusters, and GALEX UV flux is treated as unreliable for UDG 32.
The primary SED fit excludes UV because the point-spread function cannot separate filament from galaxy (Sect. 5, Appendix F); if optical light is contaminated, the SED parameters would be biased.

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Cite this review

Pith. "Pith review of Looking into the faintEst WIth MUSE (LEWIS): Exploring the nature of ultra-diffuse galaxies in the Hydra I cluster III. Untangling UDG 32 from the stripped filaments of NGC 3314A with multi-wavelength data." pith.science (2026). https://pith.science/paper/AFUB53VI

@misc{pith2026250116192,
  author       = {Pith},
  title        = {Pith review of: Looking into the faintEst WIth MUSE (LEWIS): Exploring the nature of ultra-diffuse galaxies in the Hydra I cluster III. Untangling UDG 32 from the stripped filaments of NGC 3314A with multi-wavelength data},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/AFUB53VI}},
  note         = {Machine review of arXiv:2501.16192}
}

abstract

UDG 32 is an ultra-diffuse galaxy (UDG) candidate in the Hydra I cluster that was discovered in the extended network of stellar filaments of the jellyfish galaxy NGC 3314A. This galaxy is affected by ram pressure stripping and it is hypothesised that UDG 32 may have formed from its stripped material. In this paper, we address whether UDG 32 can be associated with the stripped material of NGC 3314A and constrain its formation scenario in relation to its environment. We use new integral-field spectroscopic data from the MUSE large programme `LEWIS' in conjunction with deep multi-band photometry to constrain the kinematics and stellar populations of UDG 32. The new MUSE data allow us to reveal that the stripped material from NGC 3314A, traced by emission lines such as H$\alpha$, extends much further from its parent galaxy than previously known, completely overlapping with UDG 32 in projection, and with ram pressure induced star formation. We determine the line-of-sight velocity of UDG 32 ($v_{\rm LOS} = 3080\pm120$ km/s) and confirm that UDG 32 is part of the same kinematic structure as NGC 3314A, the Hydra I cluster south-east subgroup. By fitting the UV and optical spectral energy distribution, we constrain the stellar population properties of UDG 32. We determine its mass-weighted age to be $7.7^{+2.9}_{-2.8}$ Gyr and its metallicity to be [M/H] = $0.07^{+0.19}_{-0.32}$ dex. We confirm the presence of two globular clusters (GCs) in the MUSE field of view, bound to the Hydra I cluster rather than to UDG 32, thus part of the Hydra I intracluster GC population. The metal-rich and intermediate-age nature of UDG 32 points towards its formation from pre-enriched material in the south-east group of the Hydra I cluster that was liberated from a more massive galaxy via tidal or ram-pressure stripping, but we cannot establish a direct link to the ram-pressure stripped material from NGC 3314A.

Figures

Figures reproduced from arXiv: 2501.16192 by the authors.

**Figure 1.** Multi-wavelength view of UDG 32 and its environment. From left to right: VST OmegaCAM g-band image (Iodice et al. 2021) of UDG 32 and NGC 3314A/B with black contours tracing the H i emission detected by the MeerKAT survey (Hess et al. 2022), VST OmegaCAM colourcomposite image (Iodice et al. 2021) with the location of UDG 32 highlighted by the orange box, colour-composite derived from the MUSE data presented in this… view at source ↗

**Figure 2.** Left: Knots colour-coded by their emission-line ratios on the kernel-smoothed Hα map. In both panels, the point circled in red denotes a knot whose spectrum is likely contaminated by a background galaxy (appearing as a black feature on the kernel-smoothed Hα map). Right: BPT diagram of knots in the stripped arms of NGC 3314A with the same colour-coding. The orange line denotes the theoretical demarcation between sta… view at source ↗

**Figure 3.** summarises our results and shows the kinematic proximity of UDG 32 and the filament traced by Hα and H i gas to NGC 3314A. While we stress that we did not determine a physical distance to UDG 32, this points to a relation between NGC 3314A, its stripped gas, and UDG 32. Based on their velocities, they all seem to belong to the same foreground velocity substructure in the south-east region of the Hydra I cluster. … view at source ↗

Figures from the paper (1 more)

**Figure 4.** Figure 4: Mass-weighted age and metallicity of UDG 32 (star) derived via SED fitting in comparison to values for UDGs derived from spectroscopy (filled circles, Gannon et al. 2024) and SED fitting (open squares, Buzzo et al. 2024). The UDGs are colour-coded by their stellar mas…

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Reference graph

Works this paper leans on

13 extracted references · 12 canonical work pages · cited by 1 Pith paper

[1]

Federico II

Alabi, A., Ferré-Mateu, A., Romanowsky, A. J., et al. 2018, MNRAS, 479, 3308 Arnaboldi, M., Capaccioli, M., Mancini, D., et al. 1998, The Messenger, 93, 30 Astropy Collaboration, Price-Whelan, A. M., Sip˝ocz, B. M., et al. 2018, AJ, 156, 123 Astropy Collaboration, Robitaille, T. P., Tollerud, E. J., et al. 2013, A&A, 558, A33 Bacon, R., Accardo, M., Adjal...

arXiv 2018
[2]

For conve- nience, the top axis shows the approximate distance to NGC 3314A

The red dashed horizontal line denotes the typical extinction values in the inter- spersed dusty arms of NGC 3314A (Keel & White 2001). For conve- nience, the top axis shows the approximate distance to NGC 3314A. ratio of ionizing photon to hydrogen densities) and gas pressure (log P/k) with the NebulaBayes package (Thomas et al. 2018). Figure C.1 shows t...

work page 2024
[3]

LEWIS_udg32_arxiv with narrower wavelength range (6200 ≤ λobs ≤ 7000 Å) and slightly higher SNR (≈ 3.5)

Article number, page 11 of 17 A&A proofs: manuscript no. LEWIS_udg32_arxiv with narrower wavelength range (6200 ≤ λobs ≤ 7000 Å) and slightly higher SNR (≈ 3.5). The resulting spectrum and fit are shown in Fig. D.1b and we determine a LOS velocity of vLOS = 3085± 38 km s−1. The uncertainties are again estimated by wild bootstrapping and the posterior dist...

work page 2021
[5]

We follow the methodology in Iodice et al

For this paper, we focus on the opti- cal ugri images, as both the z-band and narrow-band Hα images have strong variations of their background level, which are of the same order as the UDG central flux. We follow the methodology in Iodice et al. (2021) to derive the magnitudes in the 5 broad-band and narrow-band H α ob- servations, i.e. first masking fore...

work page 2021
[8]

wild bootstrapping

Consider- ing the low SNR of the spectrum in this aperture 4, we restrict our analysis to the first two moments of the line-of-sight velocity distribution (LOSVD), i.e. the LOS velocity vLOS and the veloc- ity dispersion σLOS, and we only fit the optical spectrum up to λobs≤ 7100 Å. Running pPXF in conjunction with the E-M iles stellar li- brary on the op...

work page 2018
[11]

We fit the SSP models to background-subtracted spectra extracted from 8-pixel circular apertures

We mea- sure the LOS velocity of the candidate GCs using pPXF in con- junction with the E-MILES stellar library. We fit the SSP models to background-subtracted spectra extracted from 8-pixel circular apertures. However, due to the higher noise levels in the near- infrared, we only fit the optical spectra up to λmax,rest = 7000 Å. We spectroscopically conf...

work page 2023
[13]

The left panel of Fig

We also identify other emission lines at this redshift such as Hβ, [O iii], [N ii], and [Sii] that are not sky lines. The left panel of Fig. G.1 shows the spatial extent of this local diffuse emission in comparison to the footprint of the UDG and the emission related to the stripped material of NGC 3314A that we show in the right panel. The geometries of ...

work page 2013
[32]

45" 43'00

We con- struct a pseudo-narrow band image covering a 20 Å wavelength range centred onλc = 6630 Å and use this to mask all the pixels with strong Hα emission. The resulting mask is shown in blue in Fig. A.2. In addition to this mask, similar to the procedure for the other LEWIS UDGs (Iodice et al. 2023), we also mask foreground and background objects (red ...

work page 2021

Show all 13 references

[2003]

We use the inbuilt exponentially declining star-formation history (SFH) parametrised byτ, the timescale for the SF decrease and T0, the time since the SF began

and a Kroupa & Boily (2002) initial mass function (IMF). We use the inbuilt exponentially declining star-formation history (SFH) parametrised byτ, the timescale for the SF decrease and T0, the time since the SF began. Our model furthermore includes dust attenuation according t...

2002
[2007]

However, Iodice et al

FUV or NUV imaging that covered the Hydra I cluster as part of the GALEX All-Sky Imaging Sur- vey. However, Iodice et al. (2021) report UV emission associated with the filaments of NGC 3314A out to 3′.7 from its centre, in- cluding the footprint of UDG 32 (see Fig. A.1 therein...

2021
[2015]

These data (PI: R

in six bands ( ugriz and Hα: N662). These data (PI: R. Kotulla) were first presented in Hess et al. (2022) and the summary of their resolution and photometric Table B.1.Magnitudes of UDG 32 in several bands, derived in a circular aperture of 18′′.71, corrected for foreground e...

2022
[2020]

(2020) and correcting for the contamination of foreground stars, back- ground stars, and the presence of intra-cluster GCs

and Iodice et al. (2020) and correcting for the contamination of foreground stars, back- ground stars, and the presence of intra-cluster GCs. However, as shown in the LEWIS pilot paper (Iodice et al. 2023), only two optical photometric bands are not ideal for a robust GC detec...

2020
[8000]

the differences between the different ZAP runs is small. To illustrate the improved data quality following the reduc- tion above, we compare the r-band image derived from the fi- nal data cube with that derived from the quick-reduced data in Fig. A.3. We also mark three apertu...

2022

Pith tools

Reviewed August 10, 2026 · model on record in the stance chip above.

[1] [1]

Federico II

Alabi, A., Ferré-Mateu, A., Romanowsky, A. J., et al. 2018, MNRAS, 479, 3308 Arnaboldi, M., Capaccioli, M., Mancini, D., et al. 1998, The Messenger, 93, 30 Astropy Collaboration, Price-Whelan, A. M., Sip˝ocz, B. M., et al. 2018, AJ, 156, 123 Astropy Collaboration, Robitaille, T. P., Tollerud, E. J., et al. 2013, A&A, 558, A33 Bacon, R., Accardo, M., Adjal...

arXiv 2018

[2] [2]

For conve- nience, the top axis shows the approximate distance to NGC 3314A

The red dashed horizontal line denotes the typical extinction values in the inter- spersed dusty arms of NGC 3314A (Keel & White 2001). For conve- nience, the top axis shows the approximate distance to NGC 3314A. ratio of ionizing photon to hydrogen densities) and gas pressure (log P/k) with the NebulaBayes package (Thomas et al. 2018). Figure C.1 shows t...

work page 2024

[3] [3]

LEWIS_udg32_arxiv with narrower wavelength range (6200 ≤ λobs ≤ 7000 Å) and slightly higher SNR (≈ 3.5)

Article number, page 11 of 17 A&A proofs: manuscript no. LEWIS_udg32_arxiv with narrower wavelength range (6200 ≤ λobs ≤ 7000 Å) and slightly higher SNR (≈ 3.5). The resulting spectrum and fit are shown in Fig. D.1b and we determine a LOS velocity of vLOS = 3085± 38 km s−1. The uncertainties are again estimated by wild bootstrapping and the posterior dist...

work page 2021

[4] [5]

We follow the methodology in Iodice et al

For this paper, we focus on the opti- cal ugri images, as both the z-band and narrow-band Hα images have strong variations of their background level, which are of the same order as the UDG central flux. We follow the methodology in Iodice et al. (2021) to derive the magnitudes in the 5 broad-band and narrow-band H α ob- servations, i.e. first masking fore...

work page 2021

[5] [8]

wild bootstrapping

Consider- ing the low SNR of the spectrum in this aperture 4, we restrict our analysis to the first two moments of the line-of-sight velocity distribution (LOSVD), i.e. the LOS velocity vLOS and the veloc- ity dispersion σLOS, and we only fit the optical spectrum up to λobs≤ 7100 Å. Running pPXF in conjunction with the E-M iles stellar li- brary on the op...

work page 2018

[6] [11]

We fit the SSP models to background-subtracted spectra extracted from 8-pixel circular apertures

We mea- sure the LOS velocity of the candidate GCs using pPXF in con- junction with the E-MILES stellar library. We fit the SSP models to background-subtracted spectra extracted from 8-pixel circular apertures. However, due to the higher noise levels in the near- infrared, we only fit the optical spectra up to λmax,rest = 7000 Å. We spectroscopically conf...

work page 2023

[7] [13]

The left panel of Fig

We also identify other emission lines at this redshift such as Hβ, [O iii], [N ii], and [Sii] that are not sky lines. The left panel of Fig. G.1 shows the spatial extent of this local diffuse emission in comparison to the footprint of the UDG and the emission related to the stripped material of NGC 3314A that we show in the right panel. The geometries of ...

work page 2013

[8] [32]

45" 43'00

We con- struct a pseudo-narrow band image covering a 20 Å wavelength range centred onλc = 6630 Å and use this to mask all the pixels with strong Hα emission. The resulting mask is shown in blue in Fig. A.2. In addition to this mask, similar to the procedure for the other LEWIS UDGs (Iodice et al. 2023), we also mask foreground and background objects (red ...

work page 2021