Extended Star Clusters in the Remote Halo of the Intriguing Dwarf Galaxy NGC 6822

Hwang, Narae; Lee, Myung Gyoon; Lee, Jong Chul; Park, Won-Kee; Park, Hong Soo; Kim, Sang Chul; Park, Jang-Hyun

doi:10.1088/0004-637x/738/1/58

Cited by 49 publications

(57 citation statements)

References 87 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…alignment of the GCs in the Local Group dSph NGC 6822 (Hwang et al 2011;Huxor et al 2013). It remains to be shown spectroscopically whether the IKN GCs have disk kinematics or the apparent distribution is a chance alignment.…”

Section: Discussionmentioning

confidence: 96%

Optical-near-IR analysis of globular clusters in the IKN dwarf spheroidal: a complex star formation history

Tudorica

Georgiev

Chies-Santos

2015

A&A

View full text Add to dashboard Cite

Context. Age, metallicity, and spatial distribution of globular clusters (GCs) provide a powerful tool for reconstructing major starformation episodes in galaxies. IKN is a faint dwarf spheroidal (dSph) in the M 81 group of galaxies. It contains five old GCs, which makes it the galaxy with the highest known specific frequency (S N = 126). Aims. We estimate the photometric age, metallicity, and spatial distribution of the poorly studied IKN GCs. We search SDSS for GC candidates beyond the HST/ACS field of view, which covers half of IKN. Methods. To break the age-metallicity degeneracy in the V −I colour, we used WHT/LIRIS K S -band photometry and derived photometric ages and metallicities by comparison with SSP models in the V, I, K s colour space. Results. IKN GCs' V IK s colours are consistent with old ages (≥8 Gyr) and a metallicity distribution with a higher mean than is typical for such a dSph ([Fe/H] −1.4 +0.6 −0.2 dex). Their photometric mass range (0.5 < M GC < 4 × 10 5 M ) implies an unusually high mass ratio between GCs and field stars, of 10.6%. Mixture model analysis of the RGB field stars' metallicity suggests that 72% of the stars may have formed together with the GCs. Using the most massive GC−SFR relation, we calculated a star formation rate (SFR) of ∼10 M /yr during its formation epoch. We note that the more massive GCs are closer to the galaxy photometric centre. IKN GCs also appear spatially aligned along a line close to the major axis of the IKN and nearly orthogonal to the plane of spatial distribution of galaxies in the M 81 group. We identify one new IKN GC candidate based on colour and the PSF analysis of the SDSS data. Conclusions. The evidence of i) broad and high metallicity distribution of the field IKN RGB stars and its GCs, ii) high fraction, and iii) spatial alignment of IKN GCs supports a scenario for tidally triggered, complex IKN's star formation history in the context of interactions with galaxies in the M 81 group.

show abstract

Section: Discussionmentioning

confidence: 96%

Optical-near-IR analysis of globular clusters in the IKN dwarf spheroidal: a complex star formation history

Tudorica

Georgiev

Chies-Santos

2015

A&A

View full text Add to dashboard Cite

show abstract

“…The other two Local Group spiral A65, page 2 of 17 galaxies M 31 and M 33 have 20 (Huxor et al 2008;Peacock et al 2009;Huxor et al 2011a) and 2 (Stonkutė et al 2008;Cockcroft et al 2011) EOs, respectively. EOs were also found in the LMC (van den Bergh & Mackey 2004), and the dwarf irregular galaxy NGC 6822 (Hwang et al 2011).…”

Section: Eos In Late-type Galaxiesmentioning

confidence: 88%

A catalog of extended clusters and ultra-compact dwarf galaxies

Kroupa

2012

A&A

View full text Add to dashboard Cite

Context. In the past decade, very extended old stellar clusters with masses in the range from a few 10 4 to 10 8 M and effective radii larger than 10 pc have been found in various types of galaxies in different environments. Objects with masses comparable to normal globular clusters (GCs) are called extended clusters (ECs), while objects with masses in the dwarf galaxy regime are called ultra-compact dwarf galaxies (UCDs). Aims. The paper analyses the observational parameters total luminosity, M V , effective radius, r eff , and projected distance to the host galaxy, R proj , of all known ECs and UCDs and the dependence of these parameters on the type and the total luminosity of their host galaxy. Methods. We searched the available literature to compile a catalog of star clusters with effective radii larger than 10 pc. As there is no clear distinction between ECs and UCDs, both types of objects will be called extended stellar objects -abbreviated "EOs" -in this paper.Results. In total, we found 813 EOs of which 171 are associated with late-type galaxies and 642 EOs associated with early-type galaxies. EOs cover a luminosity range from about M V = −4 to −14 mag. However, the vast majority of EOs brighter than M V = −10 mag are associated with giant elliptical galaxies. At each magnitude extended objects are found with effective radii between 10 pc and an upper size limit, which shows a clear trend: the more luminous the object the larger is the upper size limit. For EOs associated with early-and late-type galaxies, the EO luminosity functions peak at −6.40 mag and −6.47 mag, respectively, which is about one magnitude fainter than the peak of the GC luminosity function. EOs and GCs form a coherent structure in the r eff vs. M V parameter space, while there is a clear gap between EOs and early-type dwarf galaxies. However, there is a small potential overlap at the high-mass end, where the most extended EOs are close to the parameters of some compact elliptical galaxies. We compare the EO sample with the numerical models of a previous paper and conclude that the parameters of the EO sample as a whole can be very well explained by a star cluster origin, where EOs are the results of merged star clusters of cluster complexes.

show abstract

“…This led Demers et al (2006) to label the system as a "polar ring galaxy." A population of remote star clusters aligned with the elongated old stellar halo have been discovered (Hwang et al 2011;Huxor et al 2013). In summary, the extended structures of NGC 6822 suggest some form of recent interaction.…”

Section: Introductionmentioning

confidence: 91%

Red Supergiant Stars as Cosmic Abundance Probes: Kmos Observations in NGC 6822

Patrick

Evans

Davies

et al. 2015

ApJ

View full text Add to dashboard Cite

We present near-IR spectroscopy of red supergiant (RSG) stars in NGC 6822, obtained with the new K-band Multi-Object Spectrograph Very Large Telescope, Chile. From comparisons with model spectra in the J-band we determine the metallicity of 11 RSGs, finding a mean value of [Z] = −0.52 ± 0.21, which agrees well with previous abundance studies of young stars and H II regions. We also find an indication for a low-significance abundance gradient within the central 1 kpc. We compare our results with those derived from older stellar populations and investigate the difference using a simple chemical evolution model. By comparing the physical properties determined for RSGs in NGC 6822 with those derived using the same technique in the Galaxy and the Magellanic Clouds, we show that there appears to be no significant temperature variation of RSGs with respect to metallicity, in contrast to recent evolutionary models.

show abstract

Extended Star Clusters in the Remote Halo of the Intriguing Dwarf Galaxy NGC 6822

Cited by 49 publications

References 87 publications

Optical-near-IR analysis of globular clusters in the IKN dwarf spheroidal: a complex star formation history

Optical-near-IR analysis of globular clusters in the IKN dwarf spheroidal: a complex star formation history

A catalog of extended clusters and ultra-compact dwarf galaxies

Red Supergiant Stars as Cosmic Abundance Probes: Kmos Observations in NGC 6822

Contact Info

Product

Resources

About