526 research outputs found
A spectroscopically confirmed z=1.327 galaxy-scale deflector magnifying a z~8 Lyman-Break galaxy in the Brightest of Reionizing Galaxies survey
We present a detailed analysis of an individual case of gravitational lensing
of a Lyman-Break galaxy (LBG) in a blank field, identified in Hubble
Space Telescope imaging obtained as part of the Brightest of Reionizing
Galaxies survey. To investigate the close proximity of the bright
() -dropout to a small group of foreground galaxies, we
obtained deep spectroscopy of the dropout and two foreground galaxies using
VLT/X-Shooter. We detect H-, H-, [OIII] and [OII] emission in
the brightest two foreground galaxies (unresolved at the natural seeing of
arcsec), placing the pair at . We can rule out emission lines
contributing all of the observed broadband flux in band at
, allowing us to exclude the candidate as a low redshift
interloper with broadband photometry dominated by strong emission lines. The
foreground galaxy pair lies at the peak of the luminosity, redshift and
separation distributions for deflectors of strongly lensed objects,
and we make a marginal detection of a demagnified secondary image in the
deepest () filter. We show that the configuration can be accurately
modelled by a singular isothermal ellipsoidal deflector and a S\'{e}rsic source
magnified by a factor of . The reconstructed source in the
best-fitting model is consistent with luminosities and morphologies of
LBGs in the literature. The lens model yields a group mass of
and a stellar mass-to-light ratio for the
brightest deflector galaxy of within its effective radius. The foreground galaxies'
redshifts would make this one of the few strong lensing deflectors discovered
at .Comment: Accepted for publication in MNRAS. 16 pages, 11 figures, 3 table
Exploring the Future of Human Factors Education; Online Learning, MOOCs, Next Generation Standards, and the Technological Skills We Need to Impart
The objective of this panel was to examine how the future of human factors education is changing given the influx of technology, a push for online learning, and adapting to the changing market. The panel will begin by Heather Lum briefly giving an overview and the precipice for this discussion panel. The panelists then provided their views and experiences regarding this topic. Kelly Steelman will discuss the potential for MOOCs and other online formats to create faster and more flexible postgraduate programs. Christina Frederick will discuss her perspectives on the technological skills we should be equipping our human factors graduates with to be successful. Nathan Sonnenfeld will give his unique take on this as an undergraduate student currently obtaining a human factors education. Susan Amato-Henderson will discuss the Next Generation Science Standards and the ramifications for educators. Lastly, Thomas Smith will focus on the advantages and disadvantages of online learning at the K-12 level. Dr. Lum will foster discussion among the panelists and questions from the general audience. Discussion time: 90 minutes
The Drosophila tango gene encodes a bHLH-PAS protein that is orthologous to mammalian Arnt and controls CNS midline and tracheal development
The Drosophila single-minded and trachealess bHLH-PAS genes control transcription and development of the CNS midline cell lineage and tracheal tubules, respectively. We show that Single-minded and Trachealess activate transcription by forming dimers with the Drosophila Tango protein that is an orthologue of the mammalian Arnt protein. Both cell culture and in vivo studies show that a DNA enhancer element acts as a binding site for both Single-minded::Tango and Trachealess::Tango heterodimers and functions in controlling CNS midline and tracheal transcription. Isolation and analysis of tango mutants reveal CNS midline and tracheal defects, and gene dosage studies demonstrate in vivo interactions between single-minded::tango and trachealess::tango. These experiments support the existence of an evolutionarily conserved, functionally diverse bHLH-PAS protein regulatory system
The Lick AGN Monitoring Project 2011: Reverberation Mapping of Markarian 50
The Lick AGN Monitoring Project 2011 observing campaign was carried out over
the course of 11 weeks in Spring 2011. Here we present the first results from
this program, a measurement of the broad-line reverberation lag in the Seyfert
1 galaxy Mrk 50. Combining our data with supplemental observations obtained
prior to the start of the main observing campaign, our dataset covers a total
duration of 4.5 months. During this time, Mrk 50 was highly variable,
exhibiting a maximum variability amplitude of a factor of 4 in the U-band
continuum and a factor of 2 in the H-beta line. Using standard
cross-correlation techniques, we find that H-beta and H-gamma lag the V-band
continuum by tau_cen = 10.64(-0.93,+0.82) and 8.43(-1.28,+1.30) days,
respectively, while the lag of He II 4686 is unresolved. The H-beta line
exhibits a symmetric velocity-resolved reverberation signature with shorter
lags in the high-velocity wings than in the line core, consistent with an
origin in a broad-line region dominated by orbital motion rather than infall or
outflow. Assuming a virial normalization factor of f=5.25, the virial estimate
of the black hole mass is (3.2+-0.5)*10^7 solar masses. These observations
demonstrate that Mrk 50 is among the most promising nearby active galaxies for
detailed investigations of broad-line region structure and dynamics.Comment: Accepted for publication in ApJ Letters. 6 pages, 4 figure
The Galaxy Zoo survey for giant AGN-ionized clouds: past and present black hole accretion events
Some active galactic nuclei (AGN) are surrounded by extended emission-line regions (EELRs), which trace both the illumination pattern of escaping radiation and its history over the light travel time from the AGN to the gas. From a new set of such EELRs, we present evidence that the AGN in many Seyfert galaxies undergo luminous episodes 0.2–2 ×105 years in duration. Motivated by the discovery of the spectacular nebula known as Hanny’s Voorwerp, ionized by a powerful AGN which has apparently faded dramatically within ≈ 105 years, Galaxy Zoo volunteers have carried out both targeted and serendipitous searches for similar emission-line clouds around low-redshift galaxies. We present the resulting list of candidates and describe spectroscopy identifying 19 galaxies with AGN-ionized regions at projected radii rproj \u3e 10 kpc. This search recovered known EELRs (such as Mrk 78, Mrk 266 and NGC 5252) and identified additional previously unknown cases, one with detected emission to r = 37 kpc. One new Sy 2 was identified. At least 14/19 are in interacting or merging systems, suggesting that tidal tails are a prime source of distant gas out of the galaxy plane to be ionized by an AGN. We see a mix of one-and two-sided structures, with observed cone angles from 23◦ to 112◦. We consider the energy balance in the ionized clouds, with lower and upper bounds on ionizing luminosity from recombination and ionization-parameter arguments, and estimate the luminosity of the core from the far-infrared data. The implied ratio of ionizing radiation seen by the clouds to that emitted by the nucleus, on the assumption of a non-variable nuclear source, ranges from 0.02 to \u3e12; 7/19 exceed unity. Small values fit well with a heavily obscured AGN in which only a small fraction of the ionizing output escapes to be traced by surrounding gas. However, large values may require that the AGN has faded over tens of thousands of years, giving us several examples of systems in which such dramatic long-period variation has occurred; this is the only current technique for addressing these time-scales in AGN history. The relative numbers of faded and non-faded objects we infer, and the projected extents of the ionized regions, give our estimate (0.2–2×105 years) for the length of individual bright phases
The Glial Regenerative Response to Central Nervous System Injury Is Enabled by Pros-Notch and Pros-NFκB Feedback
Organisms are structurally robust, as cells accommodate changes preserving structural integrity and function. The molecular mechanisms underlying structural robustness and plasticity are poorly understood, but can be investigated by probing how cells respond to injury. Injury to the CNS induces proliferation of enwrapping glia, leading to axonal re-enwrapment and partial functional recovery. This glial regenerative response is found across species, and may reflect a common underlying genetic mechanism. Here, we show that injury to the Drosophila larval CNS induces glial proliferation, and we uncover a gene network controlling this response. It consists of the mutual maintenance between the cell cycle inhibitor Prospero (Pros) and the cell cycle activators Notch and NFκB. Together they maintain glia in the brink of dividing, they enable glial proliferation following injury, and subsequently they exert negative feedback on cell division restoring cell cycle arrest. Pros also promotes glial differentiation, resolving vacuolization, enabling debris clearance and axonal enwrapment. Disruption of this gene network prevents repair and induces tumourigenesis. Using wound area measurements across genotypes and time-lapse recordings we show that when glial proliferation and glial differentiation are abolished, both the size of the glial wound and neuropile vacuolization increase. When glial proliferation and differentiation are enabled, glial wound size decreases and injury-induced apoptosis and vacuolization are prevented. The uncovered gene network promotes regeneration of the glial lesion and neuropile repair. In the unharmed animal, it is most likely a homeostatic mechanism for structural robustness. This gene network may be of relevance to mammalian glia to promote repair upon CNS injury or disease
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H0LiCOW X: Spectroscopic/imaging survey and galaxy-group identification around the strong gravitational lens system WFI2033-4723
Galaxies and galaxy groups located along the line of sight towards
gravitationally lensed quasars produce high-order perturbations of the
gravitational potential at the lens position. When these perturbation are too
large, they can induce a systematic error on of a few-percent if the lens
system is used for cosmological inference and the perturbers are not explicitly
accounted for in the lens model. In this work, we present a detailed
characterization of the environment of the lens system WFI2033-4723 (, = 0.6575), one of the core targets of the H0LICOW
project for which we present cosmological inferences in a companion paper (Rusu
et al. 2019). We use the Gemini and ESO-Very Large telescopes to measure the
spectroscopic redshifts of the brightest galaxies towards the lens, and use the
ESO-MUSE integral field spectrograph to measure the velocity-dispersion of the
lens ( km/s) and of several nearby
galaxies. In addition, we measure photometric redshifts and stellar masses of
all galaxies down to mag, mainly based on Dark Energy Survey imaging
(DR1). Our new catalog, complemented with literature data, more than doubles
the number of known galaxy spectroscopic redshifts in the direct vicinity of
the lens, expanding to 116 (64) the number of spectroscopic redshifts for
galaxies separated by less than 3 arcmin (2 arcmin) from the lens. Using the
flexion-shift as a measure of the amplitude of the gravitational perturbation,
we identify 2 galaxy groups and 3 galaxies that require specific attention in
the lens models. The ESO MUSE data enable us to measure the
velocity-dispersions of three of these galaxies. These results are essential
for the cosmological inference analysis presented in Rusu et al. (2019).Comment: Matches the version accepted for publication by MNRAS. Note that this
paper previously appeared as H0LICOW X
The Lick AGN Monitoring Project 2011: Dynamical Modeling of the Broad Line Region in Mrk 50
We present dynamical modeling of the broad line region (BLR) in the Seyfert 1
galaxy Mrk 50 using reverberation mapping data taken as part of the Lick AGN
Monitoring Project (LAMP) 2011. We model the reverberation mapping data
directly, constraining the geometry and kinematics of the BLR, as well as
deriving a black hole mass estimate that does not depend on a normalizing
factor or virial coefficient. We find that the geometry of the BLR in Mrk 50 is
a nearly face-on thick disk, with a mean radius of 9.6(+1.2,-0.9) light days, a
width of the BLR of 6.9(+1.2,-1.1) light days, and a disk opening angle of
25\pm10 degrees above the plane. We also constrain the inclination angle to be
9(+7,-5) degrees, close to face-on. Finally, the black hole mass of Mrk 50 is
inferred to be log10(M(BH)/Msun) = 7.57(+0.44,-0.27). By comparison to the
virial black hole mass estimate from traditional reverberation mapping
analysis, we find the normalizing constant (virial coefficient) to be log10(f)
= 0.78(+0.44,-0.27), consistent with the commonly adopted mean value of 0.74
based on aligning the M(BH)-{\sigma}* relation for AGN and quiescent galaxies.
While our dynamical model includes the possibility of a net inflow or outflow
in the BLR, we cannot distinguish between these two scenarios.Comment: Accepted for publication in ApJ. 8 pages, 6 figure
Constraining the dark energy equation of state with double source plane strong lenses
We investigate the possibility of constraining the dark energy equation of
state by measuring the ratio of Einstein radii in a strong gravitational lens
system with two source planes. This quantity is independent of the Hubble
parameter and directly measures the growth of angular diameter distances as a
function of redshift. We investigate the prospects for a single double source
plane system and for a forecast population of systems discovered by
re-observing a population of single source lenses already known from a
photometrically selected catalogue such as CASSOWARY or from a
spectroscopically selected catalogue such as SLACS. We find that constraints
comparable to current data-sets (15% uncertainty on the dark equation of state
at 68%CL) are possible with a handful of double source plane systems. We also
find that the method's degeneracy between Omega_M and w is almost orthogonal to
that of CMB and BAO measurements, making this method highly complimentary to
current probes.Comment: 13 Page
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