572 research outputs found
CANUCS: An Updated Mass and Magnification Model of Abell 370 with JWST
We report an updated mass and magnification model of galaxy cluster Abell 370
using new NIRCam and NIRISS data from the CAnadian NIRISS Unbiased Cluster
Survey (CANUCS). Using Lenstool and a combination of archival HST and MUSE data
with new JWST data as constraints, we derive an improved gravitational lensing
model and extract magnifications of background galaxies with uncertainties.
Using our best fit model, we perform a search for new multiply imaged systems
via predicted positions. We report no new multiply imaged systems with
identifiable redshifts, likely due to already very deep HST and Spitzer data,
but confirm a multiply imaged system by measuring its redshift with
NIRISS and NIRSpec spectra. We find that the overall shape of the critical
curve for a source at is similar to previous models of Abell 370,
with small changes. We investigate the galaxy with two images
observable with an apparent magnitude in the F125W band of and
. After correcting for the magnifications of the images,
7.2 and 8.7, we use SED fitting to find an
intrinsic stellar mass of log( = 7.35,
intrinsic SFR of 3.5 M/yr, and of
-21.3, which is close to the knee of the luminosity function at
that redshift. Our model, and corresponding magnification, shear, and
convergence maps are available on request and will be made publicly available
on MAST in a CANUCS data release (DOI: 10.17909/ph4n-6n76).Comment: 15 page
A First Look at Spatially Resolved Balmer Decrements at from JWST NIRISS Slitless Spectroscopy
We present the first results on the spatial distribution of dust attenuation
at traced by the Balmer Decrement, H/H, in
emission-line galaxies using deep JWST NIRISS slitless spectroscopy from the
CAnadian NIRISS Unbiased Cluster Survey (CANUCS). H and H
emission line maps of emission-line galaxies are extracted and stacked in bins
of stellar mass for two grism redshift bins, and
. Surface brightness profiles for the Balmer Decrement are
measured and radial profiles of the dust attenuation towards H,
, are derived. In both redshift bins, the integrated
Balmer Decrement increases with stellar mass. Lower mass
(Log(/M)) galaxies have centrally
concentrated, negative dust attenuation profiles whereas higher mass galaxies
(Log(/M)) have flat dust attenuation
profiles. The total dust obscuration is mild, with on average and
mag in the low and high redshift bins respectively. We model the
typical light profiles of star-forming galaxies at these redshifts and stellar
masses with GALFIT and apply both uniform and radially varying dust attenuation
corrections based on our integrated Balmer Decrements and radial dust
attenuation profiles. If these galaxies were observed with typical JWST NIRSpec
slit spectroscopy ( shutters), on average,
H star formation rates (SFRs) measured after slit-loss corrections
assuming uniform dust attenuation will overestimate the total SFR by and at and
respectively.Comment: 7 pages, 5 figures, submitted to ApJ
Bursty star formation and galaxy-galaxy interactions in low-mass galaxies 1 Gyr after the Big Bang
We use CANUCS JWST/NIRCam imaging of galaxies behind the
gravitationally-lensing cluster MACS J0417.5-1154 to investigate star formation
burstiness in low-mass () galaxies at .
Our sample of 123 galaxies is selected using the Lyman break selection and
photometric emission-line excess methods. Sixty per cent of the 123 galaxies in
this sample have H-to-UV flux ratios that deviate significantly from
the range of values consistent with smooth and steady star
formation histories. This large fraction indicates that the majority of
low-mass galaxies is experiencing bursty star formation histories at high
redshift. We also searched for interacting galaxies in our sample and found
that they are remarkably common ( per cent of the sample). Compared to
non-interacting galaxies, interacting galaxies are more likely to have very low
H-to-UV ratios, suggesting that galaxy-galaxy interactions enhance star
formation burstiness and enable faster quenching (with timescales of
Myr) that follows the rapid rise of star formation activity.
Given the high frequency of galaxy-galaxy interactions and the rapid SFR
fluctuations they appear to cause, we conclude that galaxy-galaxy interactions
could be a leading cause of bursty star formation in low-mass, high-
galaxies. They could thus play a significant role in the evolution of the
galaxy population at early cosmological times.Comment: 20 pages, 15 figures, and 1 table. Accepted for publication in MNRA
GeneCATānovel webtools that combine BLAST and co-expression analyses
The gene co-expression analysis toolbox (GeneCAT) introduces several novel microarray data analyzing tools. First, the multigene co-expression analysis, combined with co-expressed gene networks, provides a more powerful data mining technique than standard, single-gene co-expression analysis. Second, the high-throughput Map-O-Matic tool matches co-expression pattern of multiple query genes to genes present in user-defined subdatabases, and can therefore be used for gene mapping in forward genetic screens. Third, Rosetta combines co-expression analysis with BLAST and can be used to find ātrueā gene orthologs in the plant model organisms Arabidopsis thaliana and Hordeum vulgare (Barley). GeneCAT is equipped with expression data for the model plant A. thaliana, and first to introduce co-expression mining tools for the monocot Barley. GeneCAT is available at http://genecat.mpg.d
A Steep Decline in the Galaxy Space Density Beyond Redshift 9 in the CANUCS UV Luminosity Function
We present a new sample of 158 galaxies at redshift selected from
deep \jwst\ NIRCam imaging of five widely-separated sightlines in the CANUCS
survey. Two-thirds of the pointings and 80\% of the galaxies are covered by 12
to 14 NIRCam filters, including seven to nine medium bands, providing accurate
photometric redshifts and robustness against low redshift interlopers. A sample
of 28 galaxies at with spectroscopic redshifts shows a low systematic
offset and scatter in the difference between photometric and spectroscopic
redshifts. We derive the galaxy UV luminosity function at redshifts 8 to 12,
finding a slightly higher normalization than previously seen with \hst\ at
redshifts 8 to 10. We observe a steeper decline in the galaxy space density
from to than found by most \jwst\ Cycle 1 studies. In particular, we
find only eight galaxies at and none at , with no
galaxies brighter than F277W AB=28 or in our unmasked,
delensed survey area of 53.4 square arcminutes. We attribute the lack of bright
galaxies in CANUCS compared to GLASS and CEERS to intrinsic variance in
the galaxy density along different sightlines. The evolution in the CANUCS
luminosity function between and is comparable to that predicted by
simulations that assume a standard star formation efficiency, without invoking
any special adjustments.Comment: 30 pages, 12 figures, ApJ, in pres
CDM not dead yet: massive high-z Balmer break galaxies are less common than previously reported
Early JWST observations that targeted so-called double-break sources
(attributed to Lyman and Balmer breaks at ), reported a previously unknown
population of very massive, evolved high-redshift galaxies. This surprising
discovery led to a flurry of attempts to explain these objects' unexpected
existence including invoking alternatives to the standard CDM
cosmological paradigm. To test these early results, we adopted the same
double-break candidate galaxy selection criteria to search for such objects in
the JWST images of the CAnadian NIRISS Unbiased Cluster Survey (CANUCS), and
found a sample of 19 sources over five independent CANUCS fields that cover a
total effective area of arcmin at . However, (1) our SED
fits do not yield exceptionally high stellar masses for our candidates, while
(2) spectroscopy of five of the candidates shows that while all five are at
high redshifts, their red colours are due to high-EW emission lines in
star-forming galaxies rather than Balmer breaks in massive, evolved systems.
Additionally, (3) field-to-field variance leads to differences of
dex in the maximum stellar masses measured in the different fields, suggesting
that the early single-field JWST observations may have suffered from cosmic
variance and/or sample bias. Finally, (4) we show that the presence of even a
single massive outlier can dominate conclusions from small samples such as
those in early JWST observations. In conclusion, we find that the double-break
sources in CANUCS are not sufficiently massive or numerous to warrant
questioning the standard CDM paradigm.Comment: V2: correction of display problem of Fig.1 in Chrome browser.
Submitted to MNRAS, 10 pages (+4 in Appendix), 5 figures (+4), 1 table (+1
Laminin and biomimetic extracellular elasticity enhance functional differentiation in mammary epithelia
In the mammary gland, epithelial cells are embedded in a āsoft' environment and become functionally differentiated in culture when exposed to a laminin-rich extracellular matrix gel. Here, we define the processes by which mammary epithelial cells integrate biochemical and mechanical extracellular cues to maintain their differentiated phenotype. We used single cells cultured on top of gels in conditions permissive for Ī²-casein expression using atomic force microscopy to measure the elasticity of the cells and their underlying substrata. We found that maintenance of Ī²-casein expression required both laminin signalling and a āsoft' extracellular matrix, as is the case in normal tissues in vivo, and biomimetic intracellular elasticity, as is the case in primary mammary epithelial organoids. Conversely, two hallmarks of breast cancer development, stiffening of the extracellular matrix and loss of laminin signalling, led to the loss of Ī²-casein expression and non-biomimetic intracellular elasticity. Our data indicate that tissue-specific gene expression is controlled by both the tissues' unique biochemical milieu and mechanical properties, processes involved in maintenance of tissue integrity and protection against tumorigenesis
The MUSE Hubble Ultra Deep Field Survey:II. Spectroscopic redshifts and comparisons to color selections of high-redshift galaxies
We have conducted a two-layered spectroscopic survey (1'x1' ultra deep and 3'x3' deep regions) in the Hubble Ultra Deep Field (HUDF) with the Multi Unit Spectroscopic Explorer (MUSE). The combination of a large field of view, high sensitivity, and wide wavelength coverage provides an order of magnitude improvement in spectroscopically confirmed redshifts in the HUDF; i.e., 1206 secure spectroscopic redshifts for HST continuum selected objects, which corresponds to 15% of the total (7904). The redshift distribution extends well beyond z>3 and to HST/F775W magnitudes as faint as ~30 mag (AB, 1-sigma). In addition, 132 secure redshifts were obtained for sources with no HST counterparts that were discovered in the MUSE data cubes by a blind search for emission-line features. In total, we present 1338 high quality redshifts, which is a factor of eight increase compared with the previously known spectroscopic redshifts in the same field. We assessed redshifts mainly with the spectral features [OII] at z~20% up to 28-29 mag and ~27 mag, respectively. We used the determined redshifts to test continuum color selection (dropout) diagrams of high-z galaxies. The selection condition for F336W dropouts successfully captures ~80% of the targeted z~2.7 galaxies. However, for higher redshift selections (F435W, F606W, and F775W dropouts), the success rates decrease to ~20-40%. We empirically redefine the selection boundaries to make an attempt to improve them to ~60%. The revised boundaries allow bluer colors that capture Lya emitters with high Lya equivalent widths falling in the broadbands used for the color-color selection. Along with this paper, we release the redshift and line flux catalog
HSC-CLAUDS survey: The star formation rate functions since z ~ 2 and comparison with hydrodynamical simulations
Star formation rate functions (SFRFs) give an instantaneous view of the
distribution of star formation rates (SFRs) in galaxies at different epochs.
They are a complementary and more stringent test for models than the galaxy
stellar mass function, which gives an integrated view of the past star
formation activity. However, the exploration of SFRFs has been limited thus far
due to difficulties in assessing the SFR from observed quantities and probing
the SFRF over a wide range of SFRs. We overcome these limitations thanks to an
original method that predicts the infrared luminosity from the rest-frame
UV/optical color of a galaxy and then its SFR over a wide range of stellar
masses and redshifts. We applied this technique to the deep imaging survey
HSC-CLAUDS combined with near-infrared and UV photometry. We provide the first
SFR functions with reliable measurements in the high- and low-SFR regimes up to
and compare our results with previous observations and four
state-of-the-art hydrodynamical simulations.Comment: 29 pages, 19 figure
Regulation of mammary gland branching morphogenesis by the extracellular matrix and its remodeling enzymes.
A considerable body of research indicates that mammary gland branching morphogenesis is dependent, in part, on the extracellular matrix (ECM), ECM-receptors, such as integrins and other ECM receptors, and ECM-degrading enzymes, including matrix metalloproteinases (MMPs) and their inhibitors, tissue inhibitors of metalloproteinases (TIMPs). There is some evidence that these ECM cues affect one or more of the following processes: cell survival, polarity, proliferation, differentiation, adhesion, and migration. Both three-dimensional culture models and genetic manipulations of the mouse mammary gland have been used to study the signaling pathways that affect these processes. However, the precise mechanisms of ECM-directed mammary morphogenesis are not well understood. Mammary morphogenesis involves epithelial 'invasion' of adipose tissue, a process akin to invasion by breast cancer cells, although the former is a highly regulated developmental process. How these morphogenic pathways are integrated in the normal gland and how they become dysregulated and subverted in the progression of breast cancer also remain largely unanswered questions
- ā¦