111 research outputs found
A mass-dependent slope of the galaxy size-mass relation out to z~3: further evidence for a direct relation between median galaxy size and median halo mass
We reassess the galaxy size-mass relation out to z~3 using a new definition
of size and a sample of >29,000 galaxies from the 3D-HST, CANDELS, and
COSMOS-DASH surveys. Instead of the half-light radius r_50 we use r_80, the
radius containing 80% of the stellar light. We find that the r_80 -- M_star
relation has the form of a broken power law, with a clear change of slope at a
pivot mass M_p. Below the pivot mass the relation is shallow (r_80 \propto
M_star^0.15) and above it it is steep (r_80\propto M_star^0.6). The pivot mass
increases with redshift, from log(M_p/M_sun)~ 10.2 at z=0.4 to log(M_p/M_sun)~
10.9 at z=1.7-3. We compare these r_80-M_star relations to the M_halo-M_star
relations derived from galaxy-galaxy lensing, clustering analyses, and
abundance matching techniques. Remarkably, the pivot stellar masses of both
relations are consistent with each other at all redshifts, and the slopes are
very similar both above and below the pivot when assuming M_halo \propto
r_80^3. The implied scaling factor to relate galaxy size to halo size is r_80 /
R_vir = 0.047, independent of stellar mass and redshift.From redshift 0 to 1.5,
the pivot mass also coincides with the mass where the fraction of star-forming
galaxies is 50%, suggesting that the pivot mass reflects a transition from
dissipational to dissipationless galaxy growth. Finally, our results imply that
the scatter in the stellar-to-halo mass ratio is relatively small for massive
halos (~0.2 dex for M_halo>10^12.5 M_sun).Comment: Accepted in ApJL. Please also see complementary paper Miller et al.
201
A mass-dependent slope of the galaxy size-mass relation out to z ∼ 3 : further evidence for a direct relation between median galaxy size and median halo mass
We reassess the galaxy size-mass relation out to z similar to 3 using a new definition of size and a sample of >29,000 galaxies from the 3D-HST, CANDELS, and COSMOS-DASH surveys. Instead of the half-light radius r(50) we use r(80), the radius containing 80% of the stellar light. We find that the r(80)M(*) relation has the form of a broken power law, with a clear change of slope at a pivot mass M-p. Below the pivot mass the relation is shallow (r(80) proportional to M-*(0.)15); above it, it is steep (r(80) proportional to M-*(0.)6). The pivot mass increases with redshift, from log(M-p/M-circle dot) approximate to 10.2 at z = 0.4 to log(M-p/M-circle dot) approximate to 10.9 at z = 1.7-3. We compare these r(80)-M-* relations to the M-helo-M-* relations derived from galaxy-galaxy lensing, clustering analyses, and abundance matching techniques. Remarkably, the pivot stellar masses of both relations are consistent with each other at all redshifts, and the slopes are very similar both above and below the pivot when assuming M-halo proportional to r(8)(0)(3). The implied scaling factor to relate galaxy size to halo size is r(80)/R-vir = 0.047, independent of stellar mass and redshift. From redshift 0 to 1.5, the pivot mass also coincides with the mass where the fraction of star-forming galaxies is 50%, suggesting that the pivot mass reflects a transition from dissipational to dissipationless galaxy growth. Finally, our results imply that the scatter in the stellar-to-halo mass is relatively small for massive halos (similar to 0.2 dex for M-halo > 10(1)(2.)(5) M-circle dot)
A New View of the Size-Mass Distribution of Galaxies: Using and instead of
When investigating the sizes of galaxies it is standard practice to use the
half-light radius, . Here we explore the effects of the size definition
on the distribution of galaxies in the size -- stellar mass plane.
Specifically, we consider and , the radii that contain 20% and
80% of a galaxy's total luminosity, as determined from a Sersic profile fit,
for galaxies in the 3D-HST/CANDELS and COSMOS-DASH surveys. These radii are
calculated from size catalogs based on a simple calculation assuming a Sersic
profile. We find that the size-mass distributions for and are
markedly different from each other and also from the canonical
distribution. The most striking difference is in the relative sizes of star
forming and quiescent galaxies at fixed stellar mass. Whereas quiescent
galaxies are smaller than star forming galaxies in , this difference
nearly vanishes for . By contrast, the distance between the two
populations increases for . Considering all galaxies in a given stellar
mass and redshift bin we detect a significant bimodality in the distribution of
, with one peak corresponding to star forming galaxies and the other to
quiescent galaxies. We suggest that different measures of the size are tracing
different physical processes within galaxies; is closely related to
processes controlling the star formation rate of galaxies and may be
sensitive to accretion processes and the relation of galaxies with their halos.Comment: Resubmitted to ApJL after responding to referee's comments. Please
also see Mowla et al. submitted today as wel
High Redshift Massive Quiescent Galaxies are as Flat as Star Forming Galaxies: The Flattening of Galaxies and the Correlation with Structural Properties in CANDELS/3D-HST
We investigate the median flattening of galaxies at in all five
CANDELS/3D-HST fields via the apparent axis ratio . We separate the sample
into bins of redshift, stellar-mass, s\'ersic index, size, and UVJ determined
star-forming state to discover the most important drivers of the median
(). Quiescent galaxies at are
rounder than those at lower masses, consistent with the hypothesis that they
have grown significantly through dry merging. The massive quiescent galaxies at
higher redshift become flatter, and are as flat as star forming massive
galaxies at , consistent with formation through direct
transformations or wet mergers. We find that in quiescent galaxies,
correlations with and , and are driven by the
evolution in the s\'ersic index (), consistent with the growing accumulation
of minor mergers at lower redshift. Interestingly, does not drive these
trends fully in star-forming galaxies. Instead, the strongest predictor of
in star-forming galaxies is the effective radius, where larger galaxies are
flatter. Our findings suggest that is tracing bulge-to-total ()
galaxy ratio which would explain why smaller/more massive star-forming galaxies
are rounder than their extended/less massive analogues, although it is unclear
why s\'ersic index correlates more weakly with flattening for star forming
galaxies than for quiescent galaxies.Comment: 13 pages, 11 figures, accepted to Ap
Power scaling of an extreme ultraviolet light source for future lithography
For future lithography applications, high-power extreme ultraviolet (EUV) light sources are needed at a central wavelength of 13.5 nm within 2% bandwidth. We have demonstrated that from a physics point of view the Philips alpha-prototype source concept is scalable up to the power levels required for high-volume manufacturing (HVM) purposes. Scalability is shown both in frequency, up to 100 kHz, and pulse energy, up to 55 mJ collectable EUV per pulse, which allows us to find an optimal working point for future HVM sources within a wide parameter space. (C) 2008 American Institute of Physics
On the dearth of compact, massive, red sequence galaxies in the local universe
We set out to test the claim that the recently identified population of compact, massive, and quiescent galaxies at z similar to 2.3 must undergo significant size evolution to match the properties of galaxies found in the local universe. Using data from the Sloan Digital Sky Survey (SDSS; Data Release 7), we have conducted a search for local red sequence galaxies with sizes and masses comparable to those found at z similar to 2.3. The SDSS spectroscopic target selection algorithm excludes high surface brightness objects; we show that this makes incompleteness a concern for such massive, compact galaxies, particularly for low redshifts (z less than or similar to 0.05). We have identified 63 M(*) > 10(10.7) M(circle dot) (approximate to 5 x 10(10) M(circle dot)) red sequence galaxies at 0.066 < z(spec) < 0.12 which are smaller than the median size mass relation by a factor of 2 or more. Consistent with expectations from the virial theorem, the median offset from the mass velocity dispersion relation for these galaxies is 0.12 dex. We do not, however, find any galaxies with sizes and masses comparable to those observed at z similar to 2.3, implying a decrease in the comoving number density of these galaxies, at fixed size and mass, by a factor of greater than or similar to 5000. This result cannot be explained by incompleteness: in the 0.066 < z < 0.12 interval, we estimate that the SDSS spectroscopic sample should typically be greater than or similar to 75% complete for galaxies with the sizes and masses seen at high redshift, although for the very smallest galaxies it may be as low as similar to 20%. In order to confirm that the absence of such compact massive galaxies in SDSS is not produced by spectroscopic selection effects, we have also looked for such galaxies in the basic SDSS photometric catalog, using photometric redshifts. While we do find signs of a slight bias against massive, compact galaxies, this analysis suggests that the SDSS spectroscopic sample is missing at most a few objects in the regime we consider. Accepting the high-redshift results, it is clear that massive galaxies must undergo significant structural evolution over z less than or similar to 2 in order to match the population seen in the local universe. Our results suggest that a highly stochastic mechanism (e.g., major mergers) cannot be the primary driver of this strong size evolution
The Detection of a Red Sequence of Massive Field Galaxies at z~2.3 and its Evolution to z~0
The existence of massive galaxies with strongly suppressed star formation at
z~2.3, identified in a previous paper, suggests that a red sequence may already
be in place beyond z=2. In order to test this hypothesis, we study the
rest-frame U-B color distribution of massive galaxies at 2<z<3. The sample is
drawn from our near-infrared spectroscopic survey for massive galaxies. The
color distribution shows a statistically significant (>3 sigma) red sequence,
which hosts ~60% of the stellar mass at the high-mass end. The red-sequence
galaxies have little or no ongoing star formation, as inferred from both
emission-line diagnostics and stellar continuum shapes. Their strong Balmer
breaks and their location in the rest-frame U-B, B-V plane indicate that they
are in a post-starburst phase, with typical ages of ~0.5-1.0 Gyr. In order to
study the evolution of the red sequence, we compare our sample with
spectroscopic massive galaxy samples at 0.02<z<0.045 and 0.6<z<1.0. The
rest-frame U-B color reddens by ~0.25 mag from z~2.3 to the present at a given
mass. Over the same redshift interval, the number and stellar mass density on
the high-mass end (>10^11 Msol) of the red sequence grow by factors of ~8 and
~6, respectively. We explore simple models to explain the observed evolution.
Passive evolution models predict too strong d(U-B), and produce z~0 galaxies
that are too red. More complicated models that include aging, galaxy
transformations, and red mergers can explain both the number density and color
evolution of the massive end of the red sequence between z~2.3 and the present.Comment: Accepted for publication in the Astrophysical Journa
How Massive are Massive Compact Galaxies?
Using a sample of nine massive compact galaxies at z ~ 2.3 with rest-frame
optical spectroscopy and comprehensive U through 8um photometry we investigate
how assumptions in SED modeling change the stellar mass estimates of these
galaxies, and how this affects our interpretation of their size evolution. The
SEDs are fit to Tau-models with a range of metallicities, dust laws, as well as
different stellar population synthesis codes. These models indicate masses
equal to, or slightly smaller than our default masses. The maximum difference
is 0.16 dex for each parameter considered, and only 0.18 dex for the most
extreme combination of parameters. Two-component populations with a maximally
old stellar population superposed with a young component provide reasonable
fits to these SEDs using the models of Bruzual & Charlot (2003); however, using
models with updated treatment of TP-AGB stars the fits are poorer. The
two-component models predict masses that are 0.08 to 0.22 dex larger than the
Tau-models. We also test the effect of a bottom-light IMF and find that it
would reduce the masses of these galaxies by 0.3 dex. Considering the range of
allowable masses from the Tau-models, two-component fits, and IMF, we conclude
that on average these galaxies lie below the mass-size relation of galaxies in
the local universe by a factor of 3-9, depending on the SED models used.Comment: 5 pages, 2 figures, accepted for publication in ApJ Letter
Predicting Quiescence: The Dependence of Specific Star Formation Rate on Galaxy Size and Central Density at 0.5<z<2.5
In this paper, we investigate the relationship between star formation and
structure, using a mass-complete sample of 27,893 galaxies at
selected from 3D-HST. We confirm that star-forming galaxies are larger than
quiescent galaxies at fixed stellar mass (M). However, in contrast
with some simulations, there is only a weak relation between star formation
rate (SFR) and size within the star-forming population: when dividing into
quartiles based on residual offsets in SFR, we find that the sizes of
star-forming galaxies in the lowest quartile are 0.270.06 dex smaller than
the highest quartile. We show that 50% of star formation in galaxies at fixed
M takes place within a narrow range of sizes (0.26 dex). Taken
together, these results suggest that there is an abrupt cessation of star
formation after galaxies attain particular structural properties. Confirming
earlier results, we find that central stellar density within a 1 kpc fixed
physical radius is the key parameter connecting galaxy morphology and star
formation histories: galaxies with high central densities are red and have
increasingly lower SFR/M, whereas galaxies with low central densities
are blue and have a roughly constant (higher) SFR/M at a given
redshift. We find remarkably little scatter in the average trends and a strong
evolution of 0.5 dex in the central density threshold correlated with
quiescence from . Neither a compact size nor high- are
sufficient to assess the likelihood of quiescence for the average galaxy;
rather, the combination of these two parameters together with M
results in a unique quenching threshold in central density/velocity.Comment: 20 pages, 15 figures, and 2 tables; Accepted for publication in the
Astrophysical Journa
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