Keck Cosmic Web Imager (KCWI) spectra of globular clusters and ultracompact dwarfs in the halo of M87

Forbes, Duncan A.; Ferré-Mateu, Anna; Durré, Mark; Brodie, Jean P.; Romanowsky, Aaron J.

doi:10.1093/mnras/staa1924

Cited by 10 publications

(6 citation statements)

References 68 publications

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“…In this work, the stellar spectra are obtained in a homogeneous manner from the latest IFU at the Keck Telescope over a contiguous 250 × 300 field and have S/N of around 100 per Å for the outermost bins and above 200 per Å for central bins. The observed stellar velocity dispersions used to constrain the orbit models in this work are about 20% lower than Gebhardt et al (2011); Murphy et al (2011) beyond 1 kpc (Figure 3; top panel), but this work is in broad agreement with other recent measurements (Emsellem et al 2014;Sarzi et al 2018;Forbes et al 2020). The orbit modeling in this work allows for triaxiality, and the M BH is obtained from a full six-dimensional model parameter search with posteriors measured using a Bayesian framework.…”

Section: Black Hole Mass and Stellar Mass-to-light Ratiosupporting

confidence: 85%

“…The stellar σ at the edge of our field connects smoothly to the latest determinations of the veloc- The KCWI values within 1 kpc agree well with those from MUSE on the Very Large Telescope (Emsellem et al 2014;Sarzi et al 2018; yellow and orange respectively), while the MUSE values are 10 − 20 km s −1 larger than KCWI between 1 kpc and 3 kpc. At 4.5 kpc, our KCWI measurements match the single data point (red) from an independent KCWI observation (Forbes et al 2020). The VIRUS-P values (Murphy et al 2011;grey), which were used in the axisymmetric stellar-dynamical measurement of the M87 black hole (Gebhardt et al 2011), are 30 − 50 km s −1 higher than all other measurements.…”

Section: Stellar Velocity Dispersionsupporting

confidence: 68%

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Keck Integral-field Spectroscopy of M87 Reveals an Intrinsically Triaxial Galaxy and a Revised Black Hole Mass

Liepold

Walsh

2023

ApJL

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The three-dimensional intrinsic shape of a galaxy and the mass of the central supermassive black hole provide key insight into the galaxy’s growth history over cosmic time. Standard assumptions of a spherical or axisymmetric shape can be simplistic and can bias the black hole mass inferred from the motions of stars within a galaxy. Here, we present spatially resolved stellar kinematics of M87 over a two-dimensional 250″ × 300″ contiguous field covering a radial range of 50 pc–12 kpc from integral-field spectroscopic observations at the Keck II Telescope. From about 5 kpc and outward, we detect a prominent 25 km s−1 rotational pattern, in which the kinematic axis (connecting the maximal receding and approaching velocities) is 40° misaligned with the photometric major axis of M87. The rotational amplitude and misalignment angle both decrease in the inner 5 kpc. Such misaligned and twisted velocity fields are a hallmark of triaxiality, indicating that M87 is not an axisymmetrically shaped galaxy. Triaxial Schwarzschild orbit modeling with more than 4000 observational constraints enabled us to determine simultaneously the shape and mass parameters. The models incorporate a radially declining profile for the stellar mass-to-light ratio suggested by stellar population studies. We find that M87 is strongly triaxial, with ratios of p = 0.845 for the middle-to-long principal axes and q = 0.722 for the short-to-long principal axes, and determine the black hole mass to be ( 5.37 − 0.25 + 0.37 ± 0.22 ) × 10 9 M ⊙ , where the second error indicates the systematic uncertainty associated with the distance to M87.

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Section: Black Hole Mass and Stellar Mass-to-light Ratiosupporting

confidence: 85%

Section: Stellar Velocity Dispersionsupporting

confidence: 68%

Keck Integral-field Spectroscopy of M87 Reveals an Intrinsically Triaxial Galaxy and a Revised Black Hole Mass

Liepold

Walsh

2023

ApJL

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“…The metallicities and ages of UCDs were compiled from Mieske et al (2008); Paudel et al (2010); Francis et al (2012); Chilingarian et al (2011) and Forbes et al (2020). Where studies contained duplicate objects priority was given first to objects with properties measured by spectral fitting and then to more recent papers.…”

Section: Observational Datamentioning

confidence: 99%

Testing the tidal stripping scenario of ultra-compact dwarf galaxy formation by using internal properties

Mayes,

Drinkwater,

Pfeffer

et al. 2021

Preprint

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We use the hydrodynamical EAGLE simulation to test if ultra-compact dwarf galaxies (UCDs) can form by tidal stripping by predicting the ages and metallicities of tidally stripped galaxy nuclei in massive galaxy clusters, and compare these results to compiled observations of age and metallicities of observed UCDs. We further calculate the colours of our sample of simulated stripped nuclei using SSP models and compare these colours to observations of UCDs in the Virgo cluster. We find that the ages of observed UCDs are consistent with simulated stripped nuclei, with both groups of objects having a mean age > 9 Gyr. Both stripped nuclei and UCDs follow a similar mass-metallicity relationship, and the metallicities of observed UCDs are consistent with those of simulated stripped nuclei for objects with M > 10 7 M . The colours of observed UCDs are also consistent with our simulated stripped nuclei, for objects with M > 10 7 M , with more massive objects being redder. We find that the colours of stripped nuclei exhibit a bimodal red and blue distribution that can be explained by the dependency of colour on age and metallicity, and by the mass-colour relation. We additionally find that our low mass stripped nuclei sample is consistent with the colour of blue globular clusters. We conclude that the internal properties of simulated nuclei support the tidal stripping model of UCD formation.

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“…We note that the sample of Hou & Li (2016) is not included here as there is no information separating the UCDs from the extended stellar clusters, but there is a large overlap in objects from the previous catalogues. We also include UCDs in the Virgo cluster from different works (Liu et al 2015;Zhang et al 2018;Forbes et al 2020;96 UCDs) and a sample of 20 UCDs around NGC 3115 (Dolfi et al 2020). We also consider those compact galaxies from the compilation of Norris et al (2014), which is a mixture of both UCDs (97) and cEs (39).…”

Section: Samplementioning

confidence: 99%

A search for active galactic nuclei in low-mass compact galaxies

Ferre-Mateu,

Mezcua,

Barrows

2021

Preprint

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Low-mass compact galaxies (ultracompact dwarfs -UCDs-and compact ellipticals -cEs-) populate the stellar size-mass plane between globular clusters and early-type galaxies. Known to be formed either in-situ with an intrinsically low mass or resulting from the stripping of a more massive galaxy, the presence of a supermassive or an intermediate-mass black hole (BH) could help discriminate between these possible scenarios. With this aim, we have performed a multiwavelength search of active BH activity, i.e. active galactic nuclei (AGN), in a sample of 937 low-mass compact galaxies (580 UCDs and 357 cEs). This constitutes the largest study of AGN activity in these types of galaxies. Based on their X-ray luminosity, radio luminosity and morphology, and/or optical emission line diagnostic diagrams, we find a total of 11 cEs that host an AGN. We also study for the first time the location of both low-mass compact galaxies (UCDs and cEs) and dwarf galaxies hosting AGN on the BH-galaxy scaling relations, finding that low-mass compact galaxies tend to be overmassive in the BH mass-stellar mass plane but not as much in the BH mass-stellar velocity dispersion correlation. This, together with available BH mass measurements for some of the low-mass compact galaxies, supports a stripping origin for the majority of these objects that would contribute to the scatter seen at the low-mass end of the BH-galaxy scaling relations. However, the differences are too large to be explained solely by this scatter, and thus our results suggest that a flattening at such low-masses is also plausible, happening at a velocity dispersion of ∼20-40 km s−1.

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Keck Cosmic Web Imager (KCWI) spectra of globular clusters and ultracompact dwarfs in the halo of M87

Cited by 10 publications

References 68 publications

Keck Integral-field Spectroscopy of M87 Reveals an Intrinsically Triaxial Galaxy and a Revised Black Hole Mass

Keck Integral-field Spectroscopy of M87 Reveals an Intrinsically Triaxial Galaxy and a Revised Black Hole Mass

Testing the tidal stripping scenario of ultra-compact dwarf galaxy formation by using internal properties

A search for active galactic nuclei in low-mass compact galaxies

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