The Initial Configuration of Young Stellar Clusters: A K-Band Number Counts Analysis of the Surface Density of Stars

By R. Gutermuth, S. Megeath, J. Pipher, Jonathan P. Williams, L. Allen, P. Myers, S. Raines. 2004

165 citations recorded by the source corpus.

We present an analysis of stellar distributions for the young stellar clusters GGD 12-15, IRAS 20050+2720, and NGC 7129, which range in far-IR luminosity from 227 to 5.68 × 103 L☉ and are all still associated with their natal molecular clouds. The data used for this analysis include near-IR data obtained with FLAMINGOS on the MMT and newly obtained wide-field 850 μm emission maps from SCUBA on the JCMT. Cluster size and azimuthal asymmetry are measured via azimuthal and radial averaging methods, respectively. To quantify the deviation of the distribution of stars from circular symmetry, we define an azimuthal asymmetry parameter, and we investigate the statistical properties of this parameter through Monte Carlo simulations. The distribution of young stars is compared to the morphology of the molecular gas using stellar surface density maps and the 850 μm maps. We find that two of the clusters are not azimuthally symmetric and show a high degree of structure. The GGD 12-15 cluster is elongated and is aligned with newly detected filamentary structure at 850 μm. IRAS 20050+2720 is composed of a chain of three subclusters, in agreement with Chen and coworkers, although our results show that two of the subclusters appear to overlap. Significant 850 μm emission is detected toward two of the subclusters but is not detected toward the central subcluster, suggesting that the dense gas may already be cleared there. In contrast to these two highly embedded subclusters, we find an anticorrelation of the stars and dust in NGC 7129, indicating that much of the parental gas and dust has been dispersed. The NGC 7129 cluster exhibits a higher degree of azimuthal symmetry, a lower stellar surface density, and a larger size than the other two clusters, suggesting that the cluster may be dynamically expanding following the recent dispersal of natal molecular gas. These analyses are further evidence that embedded, forming clusters are often not spherically symmetric structures but can be elongated and clumpy and that these morphologies may reflect the initial structure of the dense molecular gas. Furthermore, this work suggests that gas expulsion by stellar feedback results in significant dynamical evolution within the first 3 Myr of cluster evolution. We estimate peak stellar volume densities and discuss the impact of these densities on the evolution of circumstellar disks and protostellar envelopes.

Subfields: Astronomy and Astrophysics, Atmospheric Science

View Paper: https://www.semanticscholar.org/paper/253d23079f48f2601a009c02daa6a7235c19683b

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Citations in the corpus

Spitzer Observations of NGC 1333: A Study of Structure and Evolution in a Nearby Embedded Cluster (2007, methodology): “PhotVis is built with heavy dependence on the FITS access and manipulation procedures and DAOphot version 1 port to IDL provided by the IDL Astronomy Users Library (Landsman 1993).”
Early Evolution of Stellar Groups and Clusters: Environmental Effects on Forming Planetary Systems (2005, background): “Toward this end, recent observational studies have determined the central densities for clusters (e.g., Gutermuth et al. 2005).”
DYNAMICAL MASS SEGREGATION ON A VERY SHORT TIMESCALE (2009, background): “It is not surprising, therefore, that very young (< 1 Myr) star clusters also show significant levels of substructure (Larson 1995; Testi et al. 2000; Elmegreen 2000; Lada & Lada 2003; Gutermuth et al. 2005; Allen et al. 2007) .”
Merging black holes in young star clusters (2019, background): “Furthermore, observations suggest that young embedded SCs are characterised by clumpiness (e.g. Cartwright & Whitworth 2004; Gutermuth et al. 2005) and high fractions of binaries (e.g. Sana et al. 2012), whereas most simulations of young SCs adopt idealized initial conditions, consisting of…”
The spatial distribution of star formation in the solar neighbourhood: do all stars form in dense clusters? (2010, methodology): “The black vertical line, which corresponds to dense clusters (as defined in Gutermuth et al. 2005), shows that < 26% of YSOs are formed in environments where they (along with their disks and planets) are likely to interact with their neighbours.”
Star Formation in the Milky Way and Nearby Galaxies (2012, background): “While various definitions of “clustered” have been used, one physically meaningful measure is a surface density of ∼ 200 YSOs pc−2 (Gutermuth et al. 2005), below which individual cores are likely to evolve in relative isolation (i.e., the timescale for infall is less than the timescale for core…”
Clustered and Triggered Star Formation in W5: Observations with Spitzer (2008, methodology): “We generate an extinction map from 2MASS H −KS colors of stars detected across the entire W5 field using the method described in Gutermuth et al. (2005) which itself is based on the NICE and NICER algorithms of Lada et al. (1994) and Lombardi & Alves (2001).”
A CORRELATION BETWEEN SURFACE DENSITIES OF YOUNG STELLAR OBJECTS AND GAS IN EIGHT NEARBY MOLECULAR CLOUDS (2011, methodology): “…rectangular grid of points in RA and Dec; this is the same procedure used to generate nearest neighbor density maps in several recent papers (e.g. Gutermuth et al. 2005; Román-Zúñiga et al. 2008; Chavarŕıa et al. 2008; Jørgensen et al. 2008; Gutermuth et al. 2008; Evans et al. 2009;…”
The relation between the most-massive star and its parental star cluster mass (2009, unknown): “…Looney (2007), 4: Kaas et al. (2004), 5: Cohen & Kuhi (1979); Briceño et al. (2002), 6: Sellgren (1983); Depoy et al. (1990); Lada et al. (1991), 7: Gutermuth et al. (2004); Wang & Looney (2007), 8: Luhman (2008), 9: Lada et al. (1991), 10: Preibisch & Zinnecker (2001); Lada & Lada (2003), 11:…”
Young Massive Star Clusters (2010, background): “From studies of star clusters that are still embedded in their natal molecular clouds, it is evident that stars form in a clumpy hierarchical fashion (Lada & Lada 2003, Gutermuth et al. 2005), and that some merging has to occur during the early (embedded) evolution.”
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Embedded star clusters and the formation of the Oort Cloud (2006, background): “The upper limit of the central density is chosen because Guthermuth et al. (2005) found a maximum central density of ρ0 = 3 × 105 M pc−3, so that an upper limit of 106 seems justified in the computations.”
The formation of very wide binaries during the star cluster dissolution phase (2010, background): “Young star clusters show a significant fraction of substructure (e.g., Larson 1995; Elmegren 2000; Testi et al. 2000; Lada & Lada 2003; Gutermuth et al. 2005; Allen et al. 2007).”
A SPITZER SURVEY OF YOUNG STELLAR CLUSTERS WITHIN ONE KILOPARSEC OF THE SUN: CLUSTER CORE EXTRACTION AND BASIC STRUCTURAL ANALYSIS (2009, methodology): “Further investigations of the structure of individual clusters using this method as well as other cluster structure indicators such as the AAP (Gutermuth et al. 2005) and Q (Cartwright & Whitworth 2004) parameters, which are not only sensitive to various asymmetries in source distributions but are…”