Observations of Thick Disks in the Hubble Space Telescope Ultra Deep Field

By Bruce G. Elmegreen, D. Elmegreen. 2006

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The vertical profiles of chain and spiral galaxies in the Hubble Space Telescope Ultra Deep Field (UDF) are fit to sech2 functions convolved with stellar profiles in order to measure the disk scale heights z0 in four passbands. The bulge regions of the spiral galaxies are avoided. Photometric redshifts give absolute scales. The rms heights of the giant clumps in these galaxies are also measured. The results indicate that UDF disks are thick, with an average z0 = 1.0 ± 0.4 kpc. The ratio of radial exponential scale length to z0 is ~3 ± 1.5. The scale heights are only 20% larger than the radii of the giant star-forming clumps and a factor of ~10 larger than the rms clump deviations around the midplanes. This suggests that the clumps formed from midplane gas and dissolved to make the thick disks. Redshifted stellar population models suggest ages of ~1 Gyr and mass column densities from 4 to 40 M☉ pc-2. The UDF disks look like young versions of modern thick disks. This resemblance is difficult to understand if galaxies grow over time or if subsequent accretion of thin disks gravitationally shrinks the observed thick disks. More likely, high-redshift disks are thick because their mass column densities are low; a velocity dispersion of only 14 km s-2 reproduces the observed thickness. Modern thick disks require more heating at high redshift. This is possible if the gas that eventually makes the thin disk is in place before the youngest age of a modern thick disk, and if the existing stars are heated during the delivery of this gas.

Subfields: Astronomy and Astrophysics, Electrical and Electronic Engineering, Instrumentation

View Paper: https://www.semanticscholar.org/paper/39f99fc5ac7cee3f76f7e33f3a4a9feb221bf8eb

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Citations in the corpus

Bulge Formation by the Coalescence of Giant Clumps in Primordial Disk Galaxies (2008, background): “At the midcourse of the simulation, the gas layer has an average scale height of 1.6 kpc, larger than the initial conditions and thicker than the star-forming layers in chain galaxies (Elmegreen & Elmegreen 2006).”
THE VERTICAL METALLICITY GRADIENT OF THE MILKY WAY DISK: TRANSITIONS IN [α/Fe] POPULATIONS (2014, background): “…analyses of external galaxies (Burstein 1979; Dalcanton & Bernstein 2002; Yoachim & Dalcanton 2008a,b), including those at redshifts as high as z ∼3 (Elmegreen & Elmegreen 2006), find that our Galaxy’s global structure is commonplace, making the Milky Way a Rosetta Stone for galaxy-formation…”
From Rings to Bulges: Evidence for Rapid Secular Galaxy Evolution at z ~ 2 from Integral Field Spectroscopy in the SINS Survey (2008, methodology): “In morphology, BX 482 resembles the young and blue clump-cluster, tadpole, or chain galaxies in the HUDF studied by Elmegreen & Elmegreen (2005, 2006) and Elmegreen et al. (2007).”
THE KMOS3D SURVEY: DESIGN, FIRST RESULTS, AND THE EVOLUTION OF GALAXY KINEMATICS FROM 0.7 ⩽ z ⩽ 2.7 (2014, methodology): “There are indications from our data and the literature that disk galaxies at z ∼ 1 − 2 are both thick (e.g. Elmegreen & Elmegreen 2006; Genzel et al. 2011) and composite (e.g. Lang et al. 2014) thus we adopt Q = 1 as an acceptable average value.”
THE METALLICITY DISTRIBUTION FUNCTIONS OF SEGUE G AND K DWARFS: CONSTRAINTS FOR DISK CHEMICAL EVOLUTION AND FORMATION (2011, background): “…our own Galaxy to disentangle the mechanisms behind disk development because the thick disk appears to be a regular feature in numerous galaxies (Burstein 1979; Dalcanton & Bernstein 2002; Yoachim & Dalcanton 2008a, 2008b), including those at redshifts as high as z ∼ 3 (Elmegreen & Elmegreen 2006).”
THE SINS SURVEY OF z ∼ 2 GALAXY KINEMATICS: PROPERTIES OF THE GIANT STAR-FORMING CLUMPS (2010, background): “…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).”
Rotational support of giant clumps in high-z disc galaxies (2011, background): “Many of the simulated galaxy properties resemble the properties of observed clumpy discs at high redshift (Genzel et al. 2006; Elmegreen & Elmegreen 2006; Genzel et al. 2008, 2011; Förster Schreiber et al. 2011), although the simulated gas fractions of 0.1-0.35 are somewhat low compared to the…”
ISM properties in hydrodynamic galaxy simulations: turbulence cascades, cloud formation, role of gravity and feedback (2010, background): “…disc with high turbulent speeds (a few tens of km s−1) and giant complexes of star formation in a thick (hz ∼ 1 kpc) gas disc (see observations by Elmegreen & Elmegreen 2006; Genzel et al. 2006; Elmegreen et al. 2007; and simulations by Semelin & Combes 2005; Bournaud et al. 2007; Agertz,…”
Rapid Formation of Exponential Disks and Bulges at High Redshift from the Dynamical Evolution of Clump-Cluster and Chain Galaxies (2007, methodology): “8) appears to be about the same thickness as the chains and edge-on spirals in the UDF, namely ∼ 1 kpc (Elmegreen & Elmegreen 2006b).”
FORMATION OF MASSIVE GALAXIES AT HIGH REDSHIFT: COLD STREAMS, CLUMPY DISKS, AND COMPACT SPHEROIDS (2009, background): “This is both evidence for in situ clump formation and a typical characteristic of observed “chain” galaxies (Elmegreen & Elmegreen 2006).”
Disc formation and the origin of clumpy galaxies at high redshift (2009, background): “Observational evidence (Elmegreen & Elmegreen 2006; Bournaud et al. 2008a; Shapiro et al. 2008) suggests that clumps form in gas-rich spiral discs rather than during on-going mergers, although the latter scenario cannot be completely ruled out (Taniguchi & Shioya 2001; Overzier et al. 2008).”
Simulations of minor mergers - I. General properties of thick discs (2008, background): “For example, Elmegreen & Elmegreen (2006) estimate that this contraction leads to a decrease in the scale-height of the contracted thick by ∼40% and an increase of the velocity dispersion by ∼50%.”
METALLICITY GRADIENTS IN THE MILKY WAY DISK AS OBSERVED BY THE SEGUE SURVEY (2011, background): “Observational support for this picture include the clump-cluster galaxies (Elmegreen & Elmegreen 2005) and the thick chain and spiral galaxies (Elmegreen & Elmegreen 2006) seen at high redshift.”
PHIBSS: MOLECULAR GAS CONTENT AND SCALING RELATIONS IN z ∼ 1–3 MASSIVE, MAIN-SEQUENCE STAR-FORMING GALAXIES (2012, background): “The UV-light distributions of edge-on ‘chain’ galaxies also indicate z-scale heights (~1 kpc) comparable to those of the ionized gas (Elmegreen & Elmegreen 2006).”
Thin, thick and dark discs in ΛCDM (2008, background): “…(Ibata et al. 2007; Martinez-Delgado et al. 2008), while thick discs appear to be ubiquitous (Tsikoudi 1977; Burstein 1979; van Dokkum et al. 1994; Matthews 2000; Dalcanton & Bernstein 2002; Pohlen et al. 2004; Ibata et al. 2005; Yoachim & Dalcanton 2005, 2006; Elmegreen & Elmegreen 2006).”
The baryonic assembly of dark matter haloes (2011, background): “…at transporting gas to their centres and may be connected to a variety of observed phenomena, including high-redshift star-forming galaxies (Elmegreen & Elmegreen 2006; Genzel et al. 2006; Dekel, Sari & Ceverino 2009b; Dekel et al. 2009a), Lyα blobs (e.g. Fardal et al. 2001; Dijkstra &…”
TRACING CHEMICAL EVOLUTION OVER THE EXTENT OF THE MILKY WAY'S DISK WITH APOGEE RED CLUMP STARS (2014, background): “Edge-on UV observations reveal that stellar disks have similar scale heights to the ionized gas in these systems (e.g., Elmegreen & Elmegreen 2006).”