75 research outputs found
The fundamental plane of evolving red nuggets
We present an exploration of the mass structure of a sample of 12 strongly
lensed massive, compact early-type galaxies at redshifts to provide
further possible evidence for their inside-out growth. We obtain new ESI/Keck
spectroscopy and infer the kinematics of both lens and source galaxies, and
combine these with existing photometry to construct (a) the fundamental plane
(FP) of the source galaxies and (b) physical models for their dark and luminous
mass structure. We find their FP to be tilted towards the virial plane relative
to the local FP, and attribute this to their unusual compactness, which causes
their kinematics to be totally dominated by the stellar mass as opposed to
their dark matter; that their FP is nevertheless still inconsistent with the
virial plane implies that both the stellar and dark structure of early-type
galaxies is non-homologous. We also find the intrinsic scatter of their FP to
be comparable to the local value, indicating that variations in the stellar
mass structure outweight variations in the dark halo in the central regions of
early-type galaxies. Finally, we show that inference on the dark halo structure
-- and, in turn, the underlying physics -- is sensitive to assumptions about
the stellar initial mass function (IMF), but that physically-motivated
assumptions about the IMF imply haloes with sub-NFW inner density slopes, and
may present further evidence for the inside-out growth of compact early-type
galaxies via minor mergers and accretion.Comment: 10 pages, 3 figures, 3 tables; submitted to MNRA
Red nuggets grow inside-out: evidence from gravitational lensing
We present a new sample of strong gravitational lens systems where both the
foreground lenses and background sources are early-type galaxies. Using imaging
from HST/ACS and Keck/NIRC2, we model the surface brightness distributions and
show that the sources form a distinct population of massive, compact galaxies
at redshifts , lying systematically below the
size-mass relation of the global elliptical galaxy population at those
redshifts. These may therefore represent relics of high-redshift red nuggets or
their partly-evolved descendants. We exploit the magnifying effect of lensing
to investigate the structural properties, stellar masses and stellar
populations of these objects with a view to understanding their evolution. We
model these objects parametrically and find that they generally require two
S\'ersic components to properly describe their light profiles, with one more
spheroidal component alongside a more envelope-like component, which is
slightly more extended though still compact. This is consistent with the
hypothesis of the inside-out growth of these objects via minor mergers. We also
find that the sources can be characterised by red-to-blue colour gradients as a
function of radius which are stronger at low redshift -- indicative of ongoing
accretion -- but that their environments generally appear consistent with that
of the general elliptical galaxy population, contrary to recent suggestions
that these objects are predominantly associated with clusters.Comment: 21 pages; accepted for publication in MNRA
Observational constraints on the sub-galactic matter-power spectrum from galaxy-galaxy strong gravitational lensing
Measuring the Hubble Constant Near and Far in the Era of ELT's
Many of the fundamental physical constants in Physics, as a discipline, are
measured to exquisite levels of precision. The fundamental constants that
define Cosmology, however, are largely determined via a handful of independent
techniques that are applied to even fewer datasets. The history of the
measurement of the Hubble Constant (H0), which serves to anchor the expansion
history of the Universe to its current value, is an exemplar of the
difficulties of cosmological measurement; indeed, as we approach the centennial
of its first measurement, the quest for H0 still consumes a great number of
resources. In this white paper, we demonstrate how the approaching era of
Extremely Large Telescopes (ELTs) will transform the astrophysical measure of
H0 from the limited and few into a fundamentally new regime where (i) multiple,
independent techniques are employed with modest use of large aperture
facilities and (ii) 1% or better precision is readily attainable. This quantum
leap in how we approach H0 is due to the unparalleled sensitivity and spatial
resolution of ELT's and the ability to use integral field observations for
simultaneous spectroscopy and photometry, which together permit both familiar
and new techniques to effectively by-pass the conventional 'ladder' framework
to minimize total uncertainty. Three independent techniques are discussed --
(i) standard candles via a two-step distance ladder applied to metal, poor
stellar populations, (ii) standard clocks via gravitational lens cosmography,
and (iii) standard sirens via gravitational wave sources -- each of which can
reach 1% with relatively modest investment from 30-m class facilities.Comment: Submitted as an Astro2020 White Paper. Please send comments to both
Rachael Beaton & Simon Birrer. Development of this paper occurred as part of
the The US Extremely Large Telescope Program Workshop in Oct 2018. We wish to
acknowledge NOAO for bringing the co-authors together, in particular the
enthusiasm and tireless leadership of Mark Dickinso
SN 2002cx: The Most Peculiar Known Type Ia Supernova
We present photometric and spectroscopic observations of supernova (SN)
2002cx, which reveal it to be unique among all observed type Ia supernovae (SNe
Ia). SN 2002cx exhibits a SN 1991T-like premaximum spectrum, a SN 1991bg-like
luminosity, and expansion velocities roughly half those of normal SNe Ia.
Photometrically, SN 2002cx has a broad peak in the band and a plateau phase
in the band, and slow late-time decline. The color evolution is
nearly normal, but the and colors are very red. Early-time
spectra of SN 2002cx evolve very quickly and are dominated by lines from
Fe-group elements; features from intermediate-mass elements (Ca, S, Si) are
weak or absent. Mysterious emission lines are observed around 7000 \AA\ at
about 3 weeks after maximum brightness. The nebular spectrum of SN 2002cx is
also unique, consisting of narrow iron and cobalt lines. The observations of SN
2002cx are inconsistent with the observed spectral/photometric sequence, and
provide a major challenge to our understanding of SNe Ia. No existing
theoretical model can successfully explain all observed aspects of SN 2002cx.Comment: 60 pages, 12 figures. A high resolution PostScript version is
available at http://astro.berkeley.edu/~weidong/sn2002cx.p
Three Gravitational Lenses for the Price of One: Enhanced Strong Lensing through Galaxy Clustering
We report the serendipitous discovery of two strong gravitational lens
candidates (ACS J160919+6532 and ACS J160910+6532) in deep images obtained with
the Advanced Camera for Surveys on the Hubble Space Telescope, each less than
40 arcsec from the previously known gravitational lens system CLASS B1608+656.
The redshifts of both lens galaxies have been measured with Keck and Gemini:
one is a member of a small galaxy group at z~0.63, which also includes the
lensing galaxy in the B1608+656 system, and the second is a member of a
foreground group at z~0.43. By measuring the effective radii and surface
brightnesses of the two lens galaxies, we infer their velocity dispersions
based on the passively evolving Fundamental Plane (FP) relation. Elliptical
isothermal lens mass models are able to explain their image configurations
within the lens hypothesis, with a velocity dispersion compatible with that
estimated from the FP for a reasonable source-redshift range. Based on the
large number of massive early-type galaxies in the field and the number-density
of faint blue galaxies, the presence of two additional lens systems around
CLASS B1608+656 is not unlikely in hindsight. Gravitational lens galaxies are
predominantly early-type galaxies, which are clustered, and the lensed quasar
host galaxies are also clustered. Therefore, obtaining deep high-resolution
images of the fields around known strong lens systems is an excellent method of
enhancing the probability of finding additional strong gravitational lens
systems.Comment: Submitted to ApJ. 8 pages, 6 figure
The Allen Telescope Array Pi GHz Sky Survey I. Survey Description and Static Catalog Results for the Bootes Field
The Pi GHz Sky Survey (PiGSS) is a key project of the Allen Telescope Array.
PiGSS is a 3.1 GHz survey of radio continuum emission in the extragalactic sky
with an emphasis on synoptic observations that measure the static and
time-variable properties of the sky. During the 2.5-year campaign, PiGSS will
twice observe ~250,000 radio sources in the 10,000 deg^2 region of the sky with
b > 30 deg to an rms sensitivity of ~1 mJy. Additionally, sub-regions of the
sky will be observed multiple times to characterize variability on time scales
of days to years. We present here observations of a 10 deg^2 region in the
Bootes constellation overlapping the NOAO Deep Wide Field Survey field. The
PiGSS image was constructed from 75 daily observations distributed over a
4-month period and has an rms flux density between 200 and 250 microJy. This
represents a deeper image by a factor of 4 to 8 than we will achieve over the
entire 10,000 deg^2. We provide flux densities, source sizes, and spectral
indices for the 425 sources detected in the image. We identify ~100$ new flat
spectrum radio sources; we project that when completed PiGSS will identify 10^4
flat spectrum sources. We identify one source that is a possible transient
radio source. This survey provides new limits on faint radio transients and
variables with characteristic durations of months.Comment: Accepted for publication in ApJ; revision submitted with extraneous
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