35 research outputs found
The COSMOS-Web ring: in-depth characterization of an Einstein ring lensing system at z~2
Aims. We provide an in-depth analysis of the COSMOS-Web ring, an Einstein
ring at z=2 that we serendipitously discovered in the COSMOS-Web survey and
possibly the most distant lens discovered to date.
Methods. We extract the visible and NIR photometry from more than 25 bands
and we derive the photometric redshifts and physical properties of both the
lens and the source with three different SED fitting codes. Using JWST/NIRCam
images, we also produce two lens models to (i) recover the total mass of the
lens, (ii) derive the magnification of the system, (iii) reconstruct the
morphology of the lensed source, and (iv) measure the slope of the total mass
density profile of the lens.
Results. The lens is a very massive and quiescent (sSFR < 10^(-13) yr-1)
elliptical galaxy at z = 2.02 \pm 0.02 with a total mass Mtot(<thetaE) = (3.66
\pm 0.36) x 10^11 Msun and a stellar mass M* = (1.37 \pm 0.14) x 10^11 Msun.
Compared to SHMRs from the literature, we find that the total mass is
consistent with the presence of a DM halo of mass Mh = 1.09^(+1.46)_(-0.57) x
10^13 Msun. In addition, the background source is a M* = (1.26 \pm 0.17) x
10^10 Msun star-forming galaxy (SFR=(78 \pm 15) Msun/yr) at z = 5.48 \pm 0.06.
Its reconstructed morphology shows two components with different colors. Dust
attenuation values from SED fitting and nearby detections in the FIR also
suggest it could be partially dust-obscured.
Conclusions. We find the lens at z=2. Its total, stellar, and DM halo masses
are consistent within the Einstein ring, so we do not need any unexpected
changes in our description of the lens (e.g. change its IMF or include a
non-negligible gas contribution). The most likely solution for the lensed
source is at z = 5.5. Its reconstructed morphology is complex and highly
wavelength dependent, possibly because it is a merger or a main sequence galaxy
with a heterogeneous dust distribution.Comment: 16 pages, submitted to A&
COSMOS-Web: Intrinsically Luminous z10 Galaxy Candidates Test Early Stellar Mass Assembly
We report the discovery of 15 exceptionally luminous
candidate galaxies discovered in the first 0.28 deg of JWST/NIRCam imaging
from the COSMOS-Web Survey. These sources span rest-frame UV magnitudes of
, and thus constitute the most intrinsically luminous
candidates identified by JWST to-date. Selected via NIRCam imaging
with Hubble ACS/F814W, deep ground-based observations corroborate their
detection and help significantly constrain their photometric redshifts. We
analyze their spectral energy distributions using multiple open-source codes
and evaluate the probability of low-redshift solutions; we conclude that 12/15
(80%) are likely genuine sources and 3/15 (20%) likely
low-redshift contaminants. Three of our candidates push the limits of
early stellar mass assembly: they have estimated stellar masses
, implying an effective stellar baryon fraction of
, where . The assembly of such stellar reservoirs is made
possible due to rapid, burst-driven star formation on timescales 100\,Myr
where the star-formation rate may far outpace the growth of the underlying dark
matter halos. This is supported by the similar volume densities inferred for
galaxies relative to
-- both about Mpc -- implying they live in halos of comparable
mass. At such high redshifts, the duty cycle for starbursts would be of order
unity, which could cause the observed change in the shape of the UVLF from a
double powerlaw to Schechter at . Spectroscopic redshift
confirmation and ensuing constraints of their masses will be critical to
understanding how, and if, such early massive galaxies push the limits of
galaxy formation in CDM.Comment: 30 pages, 9 figures; ApJ submitte
Unveiling the distant Universe: Characterizing Galaxies in the first epoch of COSMOS-Web
We report the identification of 15 galaxy candidates at using the
initial COSMOS-Web JWST observations over 77 arcmin through four NIRCam
filters (F115W, F150W, F277W, F444W) with an overlap with MIRI (F770W) of 8.7
arcmin. We fit the sample using several publicly-available SED fitting and
photometric redshift codes and determine their redshifts between and
(), UV-magnitudes between M =
21.2 and 19.5 (with M) and rest-frame
UV slopes (). These galaxies are, on average, more
luminous than most candidates discovered by JWST so far in the
literature, while exhibiting similar blue colors in their rest-frame UV. The
rest-frame UV slopes derived from SED-fitting are blue ([2.0,
2.7]) without reaching extremely blue values as reported in other recent
studies at these redshifts. The blue color is consistent with models that
suggest the underlying stellar population is not yet fully enriched in metals
like similarly luminous galaxies in the lower redshift Universe. The derived
stellar masses with MM are not in tension with the standard
CDM model and our measurement of the volume density of such UV
luminous galaxies aligns well with previously measured values presented in the
literature at . Our sample of galaxies, although compact, are
significantly resolved.Comment: Submitted to Ap
The COSMOS-Web ring: In-depth characterization of an Einstein ring lensing system at z ∼ 2
Aims. We provide an in-depth analysis of the COSMOS-Web ring, an Einstein ring at z ≈ 2 that we serendipitously discovered during the data reduction of the COSMOS-Web survey and that could be the most distant lens discovered to date.Methods. We extracted the visible and near-infrared photometry of the source and the lens from more than 25 bands. We combined these observations with far-infrared detections to study the dusty nature of the source and we derived the photometric redshifts and physical properties of both the lens and the source with three different spectral energy distribution (SED) fitting codes. Using JWST/NIRCam images, we also produced two lens models to (i) recover the total mass of the lens, (ii) derive the magnification of the system, (iii) reconstruct the morphology of the lensed source, and (iv) measure the slope of the total mass density profile of the lens.Results. We find the lens to be a very massive elliptical galaxy at z = 2.02 ± 0.02 with a total mass within the Einstein radius of Mtot(<θEin = (3.66 ± 0.36) × 1011 M⊙ and a total stellar mass of M⋆ = 1.37−0.11+0.14 × 1011 M⊙. We also estimate it to be compact and quiescent with a specific star formation rate below 10−13 yr. Compared to stellar-to-halo mass relations from the literature, we find that the total mass of the lens within the Einstein radius is consistent with the presence of a dark matter (DM) halo of total mass Mh = 1.09−0.57+1.46 × 1013 M⊙. In addition, the background source is a M⋆ = (1.26 ± 0.17) × 1010 M⊙ star-forming galaxy (SFR ≈ (78 ± 15) M⊙ yr) at z = 5.48 ± 0.06. The morphology reconstructed in the source plane shows two clear components with different colors. Dust attenuation values from SED fitting and nearby detections in the far infrared also suggest that the background source could be at least partially dust-obscured.Conclusions. We find the lens at z ≈ 2. Its total, stellar, and DM halo masses are consistent within the Einstein ring, so we do not need any unexpected changes in our description of the lens such as changing its initial mass function or including a non-negligible gas contribution. The most likely solution for the lensed source is at z ≈ 5.5. Its reconstructed morphology is complex and highly wavelength dependent, possibly because it is a merger or a main sequence galaxy with a heterogeneous dust distribution
Rencontres internationales de Bouaké. Tradition et Modernisme en Afrique Noire. 1965
Paquereau P. Rencontres internationales de Bouaké. Tradition et Modernisme en Afrique Noire. 1965. In: Revue des Sciences Religieuses, tome 39, fascicule 3, 1965. p. 296
Rencontres internationales de Bouaké. Tradition et Modernisme en Afrique Noire. 1965
Paquereau P. Rencontres internationales de Bouaké. Tradition et Modernisme en Afrique Noire. 1965. In: Revue des Sciences Religieuses, tome 39, fascicule 3, 1965. p. 296
Neogene ignimbrites in the area of Arequipa, southern Peru: paleomagnetism and welding
Based on stratigraphy, 40Ar/39Ar ages, lithofacies, trace and Sr isotopes geochemistry, and NRM directions, we correlate three main calc-alkaline to alkaline rhyolitic ignimbrites, located in and around the Arequipa depression (Paquereau et al., in press): the Rio Chili ignimbrite (RCI, ca. 13.33 Ma), the voluminous (16-24 km3) and extended (800 km2) La Joya ignimbrite (LJI, ca. 4.87 Ma), covers a large area within the Altiplano at 4500 masl.down to less than 2000 masl. south-west of the Arequipa Batholith; and the thick Arequipa Airport ignimbrite (AAI, ca. 1.65 Ma, 20 km3) consists of a lower white and an upper pink units, which fill the Arequipa depression (between 2600 and 2200 masl.) to the west of the city of Arequipa. Anisotropy of magnetic susceptibility (AMS) and characteristic remanence were measured for 52 sites located principally in the voluminous LJI and AAI as well as variation of physical properties (density, porosity, uniaxial compressive strength) of the deposits. This study deals with the magnetic properties of the deposits which help to identify the magnetic minerals and their properties and variations in and between the AAI and the LJI. Secondarily, we present variations of physical properties and magnetic properties along a 40 m thick section of the AAI, in order to map welding and recrystallisation intensities variation. The third aim focuses on Anisotropy of Magnetic Susceptibility (AMS), used to evaluate the flow directions and the transport and depositional properties of the AAI and LJI
Caractérisation des ignimbrites néogènes du bassin d'Arequipa, Pérou
Comptes Rendus Géoscience, v. 337, n. 5, p. 447-486, 2005. http://dx.doi.org/10.1016/j.crte.2004.12.004International audienc
Paleomagnetism, magnetic fabric, and Ar-40/Ar-39 dating of Pliocene and Quaternary ignimbrites in the Arequipa area, southern Peru
Ar-40/Ar-39 ages and paleomagnetic correlations using characteristic remanent magnetizations (ChRM) show that two main ignimbrite sheets were deposited at 4.86 +/- 0.07 Ma (La Joya Ignimbrite: LJI) and at 1.63 +/- 0.07 Ma (Arequipa Airport Ignimbrite: AAI) in the Arequipa area, southern Peru. The AAI is a 20-100 m-thick ignimbrite that fills in the Arequipa depression to the west of the city of Arequipa. The AAI is made up of two cooling units: an underlying white unit and an overlying weakly consolidated pink unit. Radiometric data provide the same age for the two units. As both units record exactly the same well-defined paleomagnetic direction (16 sites in the white unit of AAI: Dec=173.7; Inc=31.2; alpha 95=0.7; k=2749; and 10 sites in the pink unit of AAI; Dec=173.6; Inc=30.3; alpha 95=1.2; k=1634), showing no evidence of secular variation, the time gap between emplacement of the two units is unlikely to exceed a few years. The > 50 m thick well-consolidated white underlying unit of the Arequipa airport ignimbrite provides a very specific magnetic zonation with low magnetic susceptibilities, high coercivities and unblocking temperatures of NRM above 580 degrees C indicating a Ti-poor titanohematite signature. The Anisotropy of Magnetic Susceptibility (AMS) is strongly enhanced in this layer with anisotropy values up to 1.25. The fabric delineated by AMS was not recognized neither in the field nor in thin sections, because most of the AAI consists in a massive and isotrope deposit with no visible textural fabric. Pumices deformation due to welding is only observed at the base of the thickest sections. AMS within the AAI ignimbrite show a very well defined pattern of apparent imbrications correlated to the paleotopography, with planes of foliation and lineation dipping often at more than 20 degrees toward the expected vent, buried beneath the Nevado Chachani volcanic complex. In contrast with the relatively small extent of the thick AAI, the La Joya ignimbrite covers large areas from the Altipano down the Piedmont. Ti-poor titanomagnetites are the dominant magnetic carriers and AMS values are generally lower than 1.05. Magnetic foliations are sub horizontal and lineations directions are scattered in the LJI. The AMS fabrics are probably controlled by post-depositional compaction and welding of the deposit rather than transport dynamics