Abstract
In the third paper from the COOL–LAMPS Collaboration, we report the discovery of COOL J0542-2125, a gravitationally lensed quasar at
z
= 1.84, observed as three images due to an intervening ...massive galaxy cluster at
z
= 0.61. The lensed quasar images were identified in a search for lens systems in recent public optical imaging data and have separations on the sky up to 25.″9, wider than any previously known lensed quasar. The galaxy cluster acting as a strong lens appears to be in the process of merging, with two subclusters separated by ∼1 Mpc in the plane of the sky, and their central galaxies showing a radial velocity difference of ∼1000 km s
−1
. Both cluster cores show strongly lensed images of an assortment of background sources, as does the region between them. A preliminary strong lens model implies masses of
M
<
250
k
p
c
=
1.79
−
0.01
+
0.16
×
10
14
M
⊙
and
M
<
250
k
p
c
=
1.48
−
0.10
+
0.04
×
10
14
M
⊙
for the east and west subclusters, respectively. This line of sight is also coincident with an ROSAT ALL-sky Survey source, centered between the two confirmed cluster halos reminiscent of other major cluster-scale mergers. Archival and new follow-up imaging show flux variability in the quasar images of up to 0.4 mag within ∼1 yr, and new multicolor imaging data reveal a 2
σ
detection of the underlying quasar host. A lens system with this configuration offers rare opportunities for a range of future studies of both the lensed quasar and its host and the foreground cluster merger causing the lensing.
Abstract
We present COOL J1323+0343, an early-type galaxy at
z
= 1.0153 ± 0.0006, strongly lensed by a cluster of galaxies at
z
= 0.353 ± 0.001. This object was originally imaged by DECaLS and noted ...as a gravitational lens by COOL-LAMPS, a collaboration initiated to find strong-lensing systems in recent public optical imaging data, and confirmed with follow-up data. With ground-based
grzH
imaging and optical spectroscopy from the Las Campanas Observatory and the Nordic Optical Telescope, we derive a stellar mass, metallicity, and star formation history from stellar-population synthesis modeling. The lens modeling implies a total magnification, summed over the three images in the arc, of
μ
∼ 113. The stellar mass in the source plane is
M
*
∼ 10.64
M
⊙
and the 1
σ
upper limit on the star formation rate (SFR) in the source plane is SFR ∼ 3.75 × 10
−2
M
⊙
yr
−1
(log sSFR = −12.1 yr
−1
) in the youngest two age bins (0–100 Myr), closest to the epoch of observation. Our measurements place COOL J1323+0343 below the characteristic mass of the stellar mass function, making it an especially compelling target that could help clarify how intermediate-mass quiescent galaxies evolve. We reconstruct COOL J1323+0343 in the source plane and fit its light profile. This object is below the expected size evolution of an early-type galaxy at this mass with an effective radius r
e
∼ 0.5 kpc. This extraordinarily magnified and bright lensed early-type galaxy offers an exciting opportunity to study the morphology and star formation history of an intermediate-mass early-type galaxy in detail at
z
∼ 1.
Abstract We present a strong lensing analysis of COOL J1241+2219, the brightest known gravitationally lensed galaxy at z ≥ 5, based on new multiband Hubble Space Telescope (HST) imaging data. The ...lensed galaxy has a redshift of z = 5.043, placing it shortly after the end of the “Epoch of Reionization,” and an AB magnitude z AB = 20.47 mag (Khullar et al.). As such, it serves as a touchstone for future research of that epoch. The high spatial resolution of HST reveals internal structure in the giant arc, from which we identify 15 constraints and construct a robust lens model. We use the lens model to extract the cluster mass and lensing magnification. We find that the mass enclosed within the Einstein radius of the z = 1.001 cluster lens is M ( < 5 .″ 77 ) = 1.079 − 0.007 + 0.023 × 10 13 M ☉ , significantly lower than other known strong lensing clusters at its redshift. The average magnification of the giant arc is 〈 μ arc 〉 = 76 − 20 + 40 , a factor of 2.4 − 0.7 + 1.4 greater than previously estimated from ground-based data; the flux-weighted average magnification is 〈 μ arc 〉 = 92 − 31 + 37 . We update the current measurements of the stellar mass and star formation rate (SFR) of the source for the revised magnification to log ( M ⋆ / M ⊙ ) = 9.7 ± 0.3 and SFR = 10.3 − 4.4 + 7.0 M ⊙ yr −1 , respectively. The powerful lensing magnification acting upon COOL J1241+2219 resolves the source and enables future studies of the properties of its star formation on a clump-by-clump basis. The lensing analysis presented here will support upcoming multiwavelength characterization with HST and JWST data of the stellar mass assembly and physical properties of this high-redshift lensed galaxy.
Abstract
We report the discovery of COOL J1241+2219, a strongly lensed galaxy at redshift
z
= 5.043 ± 0.002 with observed magnitude
z
AB
= 20.47, lensed by a moderate-mass galaxy cluster at
z
... = 1.001 ± 0.001. COOL J1241+2219 is the brightest lensed galaxy currently known at optical and near-infrared wavelengths at
z
≳ 5; it is ∼5 times brighter than the prior record-holder lensed galaxy, and several magnitudes brighter than the brightest unlensed galaxies known at these redshifts. It was discovered as part of COOL-LAMPS, a collaboration initiated to find strongly lensed systems in recent public optical imaging data. We characterize the lensed galaxy, as well as the central galaxy of the lensing cluster using ground-based
grizJH
imaging and optical spectroscopy. We report model-based magnitudes, and derive stellar masses, dust content, metallicity, and star-formation rates via stellar-population synthesis modeling. Our lens mass modeling, based on ground-based imaging, implies a median source magnification of ∼30, which puts the stellar mass and star-formation rate (in the youngest age bin, closest to the epoch of observation) at log
M
*
=
10.11
−
0.26
+
0.21
and SFR =
27
−
9
+
13
M
⊙
yr
−1
, respectively. We constrain a star-formation history for COOL J1241+2219 consistent with constant star formation across ∼1 Gyr of cosmic time, and that places this galaxy on the high-mass end of the star-forming main sequence. COOL J1241+2219 is two to four times more luminous than a galaxy with the characteristic UV luminosity at these redshifts. The UV continuum slope
β
= −2.2 ± 0.2 places this galaxy on the blue side of the observed distribution of galaxies at
z
= 5, although the lack of Ly
α
emission indicates dust sufficient to suppress this emission.
We report the discovery of COOL J1241+2219, a strongly lensed galaxy at redshift z = 5.043 0.002 with observed magnitude zAB = 20.47, lensed by a moderate-mass galaxy cluster at z = 1.001 0.001. COOL ...J1241+2219 is the brightest lensed galaxy currently known at optical and near-infrared wavelengths at z 5; it is ∼5 times brighter than the prior record-holder lensed galaxy, and several magnitudes brighter than the brightest unlensed galaxies known at these redshifts. It was discovered as part of COOL-LAMPS, a collaboration initiated to find strongly lensed systems in recent public optical imaging data. We characterize the lensed galaxy, as well as the central galaxy of the lensing cluster using ground-based grizJH imaging and optical spectroscopy. We report model-based magnitudes, and derive stellar masses, dust content, metallicity, and star-formation rates via stellar-population synthesis modeling. Our lens mass modeling, based on ground-based imaging, implies a median source magnification of ∼30, which puts the stellar mass and star-formation rate (in the youngest age bin, closest to the epoch of observation) at logM* = and SFR = M yr−1, respectively. We constrain a star-formation history for COOL J1241+2219 consistent with constant star formation across ∼1 Gyr of cosmic time, and that places this galaxy on the high-mass end of the star-forming main sequence. COOL J1241+2219 is two to four times more luminous than a galaxy with the characteristic UV luminosity at these redshifts. The UV continuum slope β = −2.2 0.2 places this galaxy on the blue side of the observed distribution of galaxies at z = 5, although the lack of Ly emission indicates dust sufficient to suppress this emission.
We present a strong lensing analysis of COOL J1241+2219, the brightest known gravitationally lensed galaxy at \(z \geq 5\), based on new multi-band Hubble Space Telescope (HST) imaging data. The ...lensed galaxy has a redshift of z=5.043, placing it shortly after the end of the Epoch of Reionization, and an AB magnitude z_AB=20.47 mag (Khullar et al. 2021). As such, it serves as a touchstone for future research of that epoch. The high spatial resolution of HST reveals internal structure in the giant arc, from which we identify 15 constraints and construct a robust lens model. We use the lens model to extract cluster mass and lensing magnification. We find that the mass enclosed within the Einstein radius of the z=1.001 cluster lens is M(<5.77'')=\(1.079^{+0.023}_{-0.007}\), significantly lower than other known strong lensing clusters at its redshift. The average magnification of the giant arc is \(<\mu_{arc}>=76^{+40}_{-20}\), a factor of \(2.4^{+1.4}_{-0.7}\) greater than previously estimated from ground-based data; the flux-weighted average magnification is \(<\mu_{arc}>=92^{+37}_{-31}\) We update the current measurements of the stellar mass and star formation rate (SFR) of the source for the revised magnification, \(\log(M_\star/M_{\odot})=9.7\pm0.3\) and \({\rm SFR} = 10.3^{+7.0}_{-4.4}\) \( M_{\odot} \)yr\(^{-1}\). The powerful lensing magnification acting upon COOL J1241+2219 resolves the source and enables future studies of the properties of its star formation on a clump-by-clump basis. The lensing analysis presented here will support upcoming multiwavelength characterization with HST and JWST data of the stellar mass assembly and physical properties of this high-redshift lensed galaxy.
We compute parametric measurements of the Einstein-radius-enclosed total mass for 177 cluster-scale strong gravitational lenses identified by the ChicagO Optically-selected Lenses Located At the ...Margins of Public Surveys (COOL-LAMPS) collaboration with lens redshifts ranging from \(0.2 \lessapprox z \lessapprox 1.0\) using only two measured parameters in each lensing system: the Einstein radius, and the brightest-cluster-galaxy (BCG) redshift. We then constrain the Einstein-radius-enclosed luminosity and stellar mass by fitting parametric spectral energy distributions (SEDs) with aperture photometry from the Dark Energy Camera Legacy Survey (DECaLS) in the \(g\), \(r\), and \(z\)-band Dark Energy Camera (DECam) filters. We find that the BCG redshift, enclosed total mass, and enclosed luminosity are strongly correlated and well described by a planar relationship in 3D space. We also find that the enclosed total mass and stellar mass are correlated with a logarithmic slope of \(0.443\pm0.035\), and the enclosed total mass and stellar-to-total mass fraction are correlated with a logarithmic slope of \(-0.563\pm0.035\). The correlations described here can be used to validate strong lensing candidates in upcoming imaging surveys -- such as Rubin/Legacy Survey of Space and Time (LSST) -- in which an algorithmic treatment of lensing systems will be needed due to the sheer volume of data these surveys will produce.
In the third paper from the COOL-LAMPS Collaboration, we report the discovery of COOL J0542-2125, a gravitationally lensed quasar at \(z=1.84\), observed as three images due to an intervening massive ...galaxy cluster at \(z=0.61\). The lensed quasar images were identified in a search for lens systems in recent public optical imaging data and have separations on the sky up to 25".9, wider than any previously known lensed quasar. The galaxy cluster acting as a strong lens appears to be in the process of merging, with two sub-clusters separated by \(\sim 1\) Mpc in the plane of the sky, and their central galaxies showing a radial velocity difference of \(\sim 1000\) km/s. Both cluster cores show strongly lensed images of an assortment of background sources, as does the region between them. A preliminary strong lens model implies masses of \(M(<250\ \rm{kpc}) = 1.79^{+0.16} _{-0.01} \times 10^{14} M_{\odot}\) and \(M(<250\ \rm{kpc}) = 1.48^{+0.04}_{-0.10} \times 10^{14} M_{\odot}\) for the East and West sub-clusters, respectively. This line of sight is also coincident with a ROSAT ALL-sky Survey source, centered between the two confirmed cluster halos reminiscent of other major cluster-scale mergers.
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