A Young Stellar Cluster in the Nucleus of NGC 4449

Böker, Torsten; Marel, Roeland P. van der; Mazzuca, Lisa M.; Rix, H. W.; Rudnick, Gregory; Ho, Luis C.; Shields, J. C.

doi:10.1086/319415

Cited by 56 publications

(62 citation statements)

References 40 publications

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“…The nuclear mass estimate for NGC 4650A is higher than the masses of the star cluster nuclei derived for late-type spiral galaxies, which vary from 10 5 to 10 7 M Böker et al 2001). As already suggested by Gallagher et al (2002), this is consistent with a more luminous star cluster nucleus in NGC 4650A, for which we estimate a mass-to-light ratio M /L $1:5 M /L .…”

Section: The Nuclear Regions Of Ngc 4650asupporting

confidence: 85%

Stellar Kinematics for the Central Spheroid in the Polar Disk Galaxy NGC 4650A

Iodice¹,

Arnaboldi²,

Saglia³

et al. 2006

ApJ

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We have obtained high angular resolution, high signal-to-noise ratio spectra of the calcium triplet absorption lines on the photometric axes of the stellar spheroid in the polar disk galaxy NGC 4650A. Along the major axis, the observed rotation and velocity dispersion measurements show the presence of a kinematically decoupled nucleus and a flat velocity dispersion profile. The minor-axis kinematics is determined for the first time: along this direction some rotation is measured, and the velocity dispersion is nearly constant and slightly increases at larger distances from the center. The new high-resolution kinematic data suggest that the stellar component in NGC 4650A resembles a nearly exponential oblate spheroid supported by rotation. The main implications of these results on the previous mass models for NGC 4650A are discussed. Moreover, the new kinematic data set constraints on current models for the formation scenarios of polar ring galaxies, supporting a slow accretion rather than a secondary strong dissipative event.

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Section: The Nuclear Regions Of Ngc 4650asupporting

confidence: 85%

Stellar Kinematics for the Central Spheroid in the Polar Disk Galaxy NGC 4650A

Iodice¹,

Arnaboldi²,

Saglia³

et al. 2006

ApJ

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“…Gelatt et al (2001) derived for the SSC an age between 8−15 Myr and a mass of 2 × 10 5 M ⊙ , while Böker et al (2001) derived an age between 6−10 Myr and a lower limit for the mass of 4 × 10 5 M ⊙ . Thus, if included in our M max analysis, the SSC would provide significantly flatter slopes.…”

Section: Cluster Disruption and Infant Mortalitymentioning

confidence: 99%

“…NGC 4449 is known to host a young (∼ 6-15 Myr) central super star cluster (Böker et al 2001;Gelatt et al 2001), numerous star clusters (∼ 60, Gelatt et al (2001)) clusters with very faint ionized gas emission. Gelatt et al (2001) performed a study of the star cluster population in NGC 4449 using WFPC2 images.…”

Section: Introductionmentioning

confidence: 99%

THE CLUSTER POPULATION OF THE IRREGULAR GALAXY NGC 4449 AS SEEN BY THEHUBBLEADVANCED CAMERA FOR SURVEYS

Annibali

Tosi

Aloisi

et al. 2011

The Astronomical Journal

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We present a study of the star cluster population in the starburst irregular galaxy NGC 4449 based on B, V, I, and Hα images taken with the Advanced Camera for Surveys on the Hubble Space Telescope. We derive the cluster properties such as size, ellipticity, and total magnitudes. Cluster ages and masses are derived fitting the observed spectral energy distributions with different population synthesis models. Our analysis is strongly affected by the age-metallicity degeneracy; however, if we assume a metallicity of ∼1/4 solar, as derived from spectroscopy of HII regions, we find that the clusters have ages distributed quite continuously over a Hubble time, and they have masses from ∼ 10 3 M ⊙ up to ∼ 2 × 10 6 M ⊙ , assuming a Salpeters' IMF down to 0.1 M ⊙ . Young clusters are preferentially located in regions of young star formation, while old clusters are distributed over the whole NGC 4449 field of view, like the old stars (although we notice that some old clusters follow linear structures, possibly a reflection of past satellite accretion). The high SF activity in NGC 4449 is confirmed by its specific frequency of young massive clusters, higher than the average value found in nearby spirals and in the LMC (but lower than in other starburst dwarfs such as NGC 1705 and NGC 1569), and by the flat slope of the cluster luminosity function (dN(L V ) ∝ L −1.5 V dL for clusters younger than 1 Gyr). We use the upper envelope of the cluster log(mass) versus log(age) distribution to quantify cluster disruption, and do not find evidence for the high (90%) long-term infant mortality found by some studies. For the red clusters, we find correlations between size, ellipticity, luminosity and mass: brighter and more massive clusters tend to be more compact, and brighter clusters tend to be also more elliptical.Subject headings: galaxies: dwarf -galaxies: individual (NGC 4449) -galaxies: -3 -irregular -galaxies: star clusters: general -galaxies: starburst -4 - IntroductionStar clusters are present in all types of galaxies, from the earliest to the latest morphological types, from the quietest to the most turbulent ones, such as merging and starburst systems. They are suggested to be the birth site of many (possibly most) stars, and provide an excellent tool to study the parent galaxy evolution through a long range of epochs. For these reasons, the interest in star cluster studies never fades. While Galactic star clusters were already studied a century ago, extragalactic ones have required the Data acquisition and reduction are summarized in Section 2, while the cluster analysis and the artificial cluster experiments are described in Section 3. The results (luminosity functions, ages and masses, cluster classification, correlations between cluster properties) are presented in Section 4. In Section 5 we investigate cluster disruption. The final results and discussion are presented in Section 6. Observations and data reductionHere we briefly recall the adopted observing strategy and main steps involved in the data reduct...

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“…Subsequently, one additional galaxy in our sample (ESO 418À008) has also been found to possess a compact star cluster nucleus based on HST imaging (Bö ker et al 2002;Windhorst et al 2002). Although the formation mechanism for these compact nuclei at the centers of such diffuse galaxies with shallow central potentials remains a mystery, these types of '' naked '' nuclei are now known to be commonplace at the centers of late-type, pure disk spirals (see also van den Bergh 1995;Phillips et al 1996;Bö ker et al 2001Bö ker et al , 2002.…”

Section: Kinematic Signatures Of Semi-stellar Nuclei In Extreme Late-mentioning

confidence: 99%

High‐Resolution Optical Rotation Curves of Low‐Luminosity Spiral Galaxies

Matthews¹,

Gallagher²

2002

ASTROPHYS J SUPPL S

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We present optical long-slit spectroscopic observations of 21 low-luminosity, extreme late-type spiral galaxies. Our sample is comprised of Sc-Sm Local Supercluster spirals with moderate-to-low optical surface brightnesses and with luminosities at the low end for spiral disk galaxies (M V ! À18:8). For each galaxy we have measured high spatial resolution position-velocity (P-V) curves using the H emission line, and for 15 of the galaxies we also derive major-axis rotation curves. In $50% of our sample, the P-V curves show significant asymmetries in shape, extent, and/or amplitude on the approaching and receding sides of the disk. A number of the P-V curves are still rising to the last measured point or reach a clear turnover on only one side. In most instances we find good agreement between the kinematic centers of extreme late-type spirals as defined by the global H i emission profile and by their optical continuum, although in a few cases we see evidence of possible real offsets. In spite of their shallow central gravitational potentials, at least six of the galaxies in our sample possess semi-stellar nuclei that appear to be compact nuclear star clusters; in five of these cases we see kinematic signatures in the P-V curves at the location of the nucleus. Finally, we find that like giant spirals, our sample galaxies have higher specific angular momenta than predicted by current cold dark matter models.

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A Young Stellar Cluster in the Nucleus of NGC 4449

Cited by 56 publications

References 40 publications

Stellar Kinematics for the Central Spheroid in the Polar Disk Galaxy NGC 4650A

Stellar Kinematics for the Central Spheroid in the Polar Disk Galaxy NGC 4650A

THE CLUSTER POPULATION OF THE IRREGULAR GALAXY NGC 4449 AS SEEN BY THEHUBBLEADVANCED CAMERA FOR SURVEYS

High‐Resolution Optical Rotation Curves of Low‐Luminosity Spiral Galaxies

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