Stellar Populations in 10 Clump-Cluster Galaxies of the Hubble Ultra Deep Field

By Bruce G. Elmegreen, D. Elmegreen. 2005

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Color-color diagrams for the clump and interclump emission in 10 clump-cluster galaxies of the Hubble Ultra Deep Field (UDF) are made from B,V, i, and z images and compared with models to determine redshifts, star formation histories, and galaxy masses. These galaxies are members of a class dominated by 5-10 giant clumps, with no exponential disk or bulge. The redshifts are found to be in the range from 1.6 to 3. The clump emission is typically 40% of the total galaxy emission, and the luminous clump mass is 19% of the total galaxy mass. The clump colors suggest declining star formation over the last ~0.3 Gyr, while the interclump emission is redder than the clumps, corresponding to a greater age. The clump luminous masses are typically 6 × 108 M☉, and their diameters average 1.8 kpc, making their average density ~0.2 M☉ pc-3. Including the interclump populations, assumed to begin forming at z = 6, the total galaxy luminous masses average 6.5 × 1010 M☉ and their diameters average 19 kpc to the 2 σ noise level. The expected galaxy rotation speeds average ~150 km s-1 if they are uniformly rotating disks. The ages of the clumps are longer than their internal dynamical times by a factor of ~8, so they are stable star clusters, but the clump densities are only ~10 times the limiting tidal densities, so they could be deformed by tidal forces. This is consistent with the observation that some clumps have tails. The clumps could form by gravitational instabilities in accreting disk gas and then disperse on a ~1 Gyr timescale, building up the interclump disk emission, or they could be captured as gas-rich dwarf galaxies, flaring up with star formation at first and then dispersing. Support for this second possibility comes from the high abundance of nearly identical clumps in the UDF, smaller than 6 pixels, whose distributions on color-magnitude and color-color plots are the same as the galaxy clumps studied here. The distribution of axial ratios for the combined population of chain and clump-cluster galaxies in the UDF is compared with models and shown to be consistent with a thick-disk geometry. If these galaxies evolve into today's disk galaxies, then we are observing a stage in which accretion and star formation are extremely clumpy and the resulting high velocity dispersions form thick disks. Several clump-clusters have disk densities that are much larger than in local disks, however, suggesting an alternate model in which they do not survive until today, but get converted into ellipticals by collisions.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/67f22f86c6f25085f2a4ff2cfe904b82b45e695e

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Citations in the corpus

EVIDENCE FOR A CLUMPY, ROTATING GAS DISK IN A SUBMILLIMETER GALAXY AT z = 4 (2012, background): “Rest–frame UV/optical imaging shows that, unlike low–redshift galaxies, their disks tend to be broken into multiple giant clumps of ∼1 kpc and 109 M⊙ (Elmegreen et al. 2004; Elmegreen & Elmegreen 2005; Förster Schreiber et al. 2006; Genzel et al. 2008).”
On the fraction of star formation occurring in bound stellar clusters (2012, background): “…star-forming galaxies appear to be ‘normal’ star-forming (albeit unstable) disc galaxies, of which the high SFRs are simply caused by their substantial gas reservoir (Elmegreen & Elmegreen 2005; Erb et al. 2006; Genzel et al. 2008; Elmegreen et al. 2009; Daddi et al. 2010; Tacconi et al. 2010).”
High-redshift clumpy discs and bulges in cosmological simulations (2009, background): “In a typical z ∼ 2 disc, 10–40 per cent of its UV rest frame light is emitted from a few clumps of a characteristic size ∼1 kpc, and with a high SFR of tens of M yr−1 each (Elmegreen, Elmegreen & Sheets 2004a; Elmegreen & Elmegreen 2005; Förster Schreiber et al. 2006; Genzel et al. 2008).”
SHORT-LIVED STAR-FORMING GIANT CLUMPS IN COSMOLOGICAL SIMULATIONS OF z ≈ 2 DISKS (2010, unknown): “The typical clump-to-disk mass ratio reported in Elmegreen & Elmegreen (2005) is 1%, and in Förster Schreibe et al. (2011b) it is roughly 2%.”
CONSTRAINTS ON THE ASSEMBLY AND DYNAMICS OF GALAXIES. I. DETAILED REST-FRAME OPTICAL MORPHOLOGIES ON KILOPARSEC SCALE OF z ∼ 2 STAR-FORMING GALAXIES (2010, background): “…remarkable case, the other disks among our NIC2 targets as well as other highz samples studied at high resolution (e.g., Bournaud et al. 2008; Elmegreen & Elmegreen 2005; Elmegreen et al. 2009; Genzel et al. 2010, and Paper II) show prominent clumps and properties consistent with the above…”
BULGE AND CLUMP EVOLUTION IN HUBBLE ULTRA DEEP FIELD CLUMP CLUSTERS, CHAINS AND SPIRAL GALAXIES (2008, methodology): “Clump masses measured from photometry range from 107 M to 109 M in stars (e.g., Elmegreen & Elmegreen 2005; Elmegreen et al. 2007b); gas masses are not observed yet.”
Bulge Formation by the Coalescence of Giant Clumps in Primordial Disk Galaxies (2008, background): “These clumps are large (>1 kpc), massive ( 108 M ), and young ( 300Myr, or 10 internal dynamical times), making them look like scaled-up star complexes formed by common gravitational instabilities (Elmegreen & Elmegreen 2005; Elmegreen et al. 2007a).”
The Morphological Diversities among Star-forming Galaxies at High Redshifts in the Great Observatories Origins Deep Survey (2006, background): “Similar types of galaxies with lown or flatter than exponential profiles have also been identified previously in deepHST surveys (Marleau & Simard 1998; Elmegreen, Elmegreen, & Sheets 2004; Elmegreen, Elmegreen, & Hirst 2004; Elmegreen & Elmegreen 2005).”
Observations of Thick Disks in the Hubble Space Telescope Ultra Deep Field (2006, background): “We found the same for spirals and chain galaxies in the Tadpole Galaxy background field (Elmegreen, et al. 2004b, hereafter EEH04) and the UDF (Elmegreen & Elmegreen 2005, hereafter EE05; Elmegreen et al. 2005a; hereafter EERS).”
THE LONG LIVES OF GIANT CLUMPS AND THE BIRTH OF OUTFLOWS IN GAS-RICH GALAXIES AT HIGH REDSHIFT (2013, background): “Typically, a clumpy star-forming galaxy of stellar mass of a few 1010−11M⊙ at redshift z ≈ 1 − 3 contains a handful of kpc-sized clumps containing each a few 108−9M⊙ of gas and stars (Elmegreen & Elmegreen 2005; Genzel et al. 2011).”
Radiative feedback and the low efficiency of galaxy formation in low-mass haloes at high redshift (2013, background): “However, these GMCs should not be confused with the giant clumps seen in more massive, marginally unstable discs (Noguchi 1999; Elmegreen & Elmegreen 2005; Bournaud et al. 2007; Genzel et al. 2008; Dekel et al. 2009; Agertz et al. 2009; Ceverino et al. 2010, 2012; Mandelker et al. 2013).”
THICK DISKS OF EDGE-ON GALAXIES SEEN THROUGH THE SPITZER SURVEY OF STELLAR STRUCTURE IN GALAXIES (S4G): LAIR OF MISSING BARYONS? (2011, background): “…the disk may have been mostly heated in a short interval of time at the beginning of the history of the galaxy, an epoch in which there is a large population of clumpy disks whose clumps formed through disk gravitational instabilities and had a mass of a few 108 M (Elmegreen & Elmegreen 2005).”
THE SINS SURVEY OF z ∼ 2 GALAXY KINEMATICS: PROPERTIES OF THE GIANT STAR-FORMING CLUMPS (2010, methodology): “…Noeske et al. 2007; Daddi et al. 2007; Cameron et al. 2010) are irregular and often dominated by several giant (kpc size) star-forming clumps (Cowie et al. 1995; van den Bergh et al. 1996; Elmegreen et al. 2004, 2007, 2009; Elmegreen & Elmegreen 2005, 2006; Förster Schreiber et al. 2009, 2011).”
Structural Parameters of Thin and Thick Disks in Edge-on Disk Galaxies (2005, methodology): “Elmegreen & Elmegreen (2005) argue persuasively that these systems will wind up in a thickened disk with high velocity dispersion and are thus likely precursors to thick disks.”
Rapid Formation of Exponential Disks and Bulges at High Redshift from the Dynamical Evolution of Clump-Cluster and Chain Galaxies (2007, background): “…that chain and clump-cluster galaxies are mostly a single class of objects that are clumpy disks viewed in different orientations: the two types have equivalent sizes, magnitudes, and redshift ranges, and their clumps have similar properties (Elmegreen & Elmegreen 2005, hereafter EE05, and EERC07).”
FORMATION OF MASSIVE GALAXIES AT HIGH REDSHIFT: COLD STREAMS, CLUMPY DISKS, AND COMPACT SPHEROIDS (2009, background): “…gas-rich, thick turbulent disks into big clumps, and the subsequent migration into a central bulge, have been proposed (van den Bergh et al. 1996; Elmegreen & Elmegreen 2005; Genzel et al. 2008; Bournaud et al. 2008) and successfully simulated for idealized disks in isolation (Noguchi 1999;…”
Physical Models of Galaxy Formation in a Cosmological Framework (2014, background): “With the discovery of clumpy disks at z ∼ 2 (Elmegreen & Elmegreen 2005, Förster Schreiber et al. 2009), the abundant clumps that formed in simulations without ISM pressurization began to be touted as a “feature” (Bournaud et al. 2007, Ceverino et al. 2010, Dekel et al. 2009).”