We analyze spectra of a gravitationally lensed galaxy, known as the Sunburst Arc, that is leaking ionizing photons, also known as the Lyman continuum (LyC). Magnification from gravitational lensing ...permits the galaxy to be spatially resolved into one region that leaks ionizing photons, and several that do not. Rest-frame ultraviolet and optical spectra from Magellan target ten different regions along the lensed Arc, including six multiple images of the LyC leaking region, as well as four regions that do not show LyC emission. The rest-frame optical spectra of the ionizing photon emitting regions reveal a blue-shifted (\(\Delta V\)=27 km s\(^{-1}\)) broad emission component (FWHM=327 km s\(^{-1}\)) comprising 55% of the total OIII line flux, in addition to a narrow component (FWHM = 112 km s\(^{-1}\)), suggesting the presence of strong highly ionized gas outflows. This is consistent with the high-velocity ionized outflow inferred from the rest-frame UV spectra. In contrast, the broad emission component is less prominent in the non-leaking regions, comprising \(\sim\)26% of total OIII line flux. The high ionization absorption lines are prominent in both leaker and non-leaker but low ionization absorption lines are very weak in the leaker, suggesting that the line of sight gas is highly ionized in the leaker. Analyses of stellar wind features reveal that the stellar population of the LyC leaking regions is considerably younger (\(\sim\)3 Myr) than the non-leaking regions (\(\sim\)12 Myr), highlighting that stellar feedback from young stars may play an important role in ionizing photon escape.
We present a strong lensing analysis of the cluster PSZ1 G311.65-18.48, based on Hubble Space Telescope imaging, archival VLT/MUSE spectroscopy, and Chandra X-ray data. This cool-core cluster ...(z=0.443) lenses the brightest lensed galaxy known, dubbed the "Sunburst Arc" (z=2.3703), a Lyman continuum (LyC) emitting galaxy multiply-imaged 12 times. We identify in this field 14 additional strongly-lensed galaxies to constrain a strong lens model, and report secure spectroscopic redshifts of four. We measure a projected cluster core mass of M(<250 kpc)=2.93+0.01/-0.02x10^14M_sun. The two least-magnified but complete images of the Sunburst Arc's source galaxy are magnified by ~13x, while the LyC clump is magnified by ~4-80x. We present time delay predictions and conclusive evidence that a discrepant clump in the Sunburst Arc, previously claimed to be a transient, is not variable, thus strengthening the hypothesis that it results from an exceptionally high magnification. A source plane reconstruction and analysis of the Sunburst Arc finds its physical size to be 1x2 kpc, and that it is resolved in three distinct directions in the source plane, 0, 40, and 75 degrees (east of North). We place an upper limit of r <~ 50 pc on the source plane size of unresolved clumps, and r<~ 32 pc for the LyC clump. Finally, we report that the Sunburst Arc is likely in a system of two or more galaxies separated by <~6 kpc in projection. Their interaction may drive star formation and could play a role in the mechanism responsible for the leaking LyC radiation.
We image the spatial extent of a cool galactic outflow with fine structure Fe
II$^*$ emission and resonant Mg II emission in a gravitationally lensed
star-forming galaxy at $z = 1.70347$. The Fe ...II$^*$ and Mg II
(continuum-subtracted) emissions span out to radial distances of $\sim$14.33
kpc and 26.5 kpc, respectively, with maximum spatial extents of $\sim$21 kpc
for Fe II$^*$ emission and $\sim$30 kpc for Mg II emission. Mg II residual
emission is patchy and covers a total area of $\sim$184 kpc$^2$, constraining
the minimum area covered by the outflowing gas to be $\sim$13% of the total
area. Mg II emission is asymmetric and shows $\sim$21% more extended emission
along the declination direction. We constrain the covering fractions of the Fe
II$^*$ and Mg II emission as a function of radial distance and characterize
them with a power law model. The Mg II 2803 emission line shows two
kinematically distinct emission components, and may correspond to two distinct
shells of outflowing gas with a velocity separation of $\Delta v \sim$ 400
km/s. By using multiple images with different magnifications of the galaxy in
the image plane, we trace the Fe II$^*$, Mg II emissions around three
individual star-forming regions. In all cases, both the Fe II$^*$ and Mg II
emissions are more spatially extended compared to the star forming regions
traced by the O II emission. These findings provide robust constraints on the
spatial extent of the outflowing gas, and combined with outflow velocity and
column density measurements will give stringent constraints on mass outflow
rates of the galaxy.
Galaxy clusters magnify background objects through strong gravitational lensing. Typical magnifications for lensed galaxies are factors of a few but can also be as high as tens or hundreds, ...stretching galaxies into giant arcs. Individual stars can attain even higher magnifications given fortuitous alignment with the lensing cluster. Recently, several individual stars at redshift \(z \sim 1 - 1.5\) have been discovered, magnified by factors of thousands, temporarily boosted by microlensing. Here we report observations of a more distant and persistent magnified star at redshift \(z_{\rm phot} = 6.2 \pm 0.1\), 900 Myr after the Big Bang. This star is magnified by a factor of thousands by the foreground galaxy cluster lens WHL0137--08 (\(z = 0.566\)), as estimated by four independent lens models. Unlike previous lensed stars, the magnification and observed brightness (AB mag 27.2) have remained roughly constant over 3.5 years of imaging and follow-up. The delensed absolute UV magnitude \(M_{UV} = -10 \pm 2\) is consistent with a star of mass \(M > 50 M_{\odot}\). Confirmation and spectral classification are forthcoming from approved observations with the James Webb Space Telescope
We present spatially resolved analysis of a lensed galaxy, SDSS1958+5950 at
$z = 2.225$, from the Cambridge Sloan Survey of Wide Arcs in the Sky
(CASSOWARY). We use our new high resolution imaging ...data to construct a robust
lens model for the galaxy group at $z = 0.214$. We employ the updated lens
model to combine the Integral Field Spectrographic observations on two highly
distorted images of the lensed target. We adopt a forward-modeling approach to
deconvolve the effects of point spread function from the combined source-plane
reconstruction. The approach is adapted to the lens model magnification and
enables a resolution of $\sim$170 pc in the galaxy-source plane. We propose an
ongoing merger as the origin of the lensed system on the basis of its
source-plane morphology, kinematics and rest-frame emission line ratios. Using
our novel technique of adaptive coadded source plane reconstruction, we are
able to detect different components in the velocity gradient that were not seen
in previous studies of this object, plausibly belonging to different components
in the merging system.
The gravitationally lensed star WHL0137-LS, nicknamed Earendel, was
identified with a photometric redshift $z_{phot} = 6.2 \pm 0.1$ based on images
taken with the Hubble Space Telescope. Here we ...present James Webb Space
Telescope (JWST) Near Infrared Camera (NIRCam) images of Earendel in 8 filters
spanning 0.8--5.0$\mu$m. In these higher resolution images, Earendel remains a
single unresolved point source on the lensing critical curve, increasing the
lower limit on the lensing magnification to $\mu > 4000$ and restricting the
source plane radius further to $r < 0.02$ pc, or $\sim 4000$ AU. These new
observations strengthen the conclusion that Earendel is best explained by an
individual star or multiple star system, and support the previous photometric
redshift estimate. Fitting grids of stellar spectra to our photometry yields a
stellar temperature of $T_{\mathrm{eff}} \simeq 13000$--16000 K assuming the
light is dominated by a single star. The delensed bolometric luminosity in this
case ranges from $\log(L) = 5.8$--6.6 $L_{\odot}$, which is in the range where
one expects luminous blue variable stars. Follow-up observations, including
JWST NIRSpec scheduled for late 2022, are needed to further unravel the nature
of this object, which presents a unique opportunity to study massive stars in
the first billion years of the universe.
We present the spatially resolved measurements of a cool galactic outflow in the gravitationally lensed galaxy RCS0327 at \(z \approx 1.703\) using VLT/MUSE IFU observations. We probe the cool ...outflowing gas, traced by blueshifted Mg II and Fe II absorption lines, in 15 distinct regions of the same galaxy in its image-plane. Different physical regions, 5 to 7 kpc apart within the galaxy, drive the outflows at different velocities (\(V_{out} \sim \) \(-161\) to \(-240\) km s\(^{-1}\)), and mass outflow rates (\(\dot{M}_{out} \sim\) 183 to 527 \(M_{\odot}\ yr^{-1}\)). The outflow velocities from different regions of the same galaxy vary by 80 km s\(^{-1}\), which is comparable to the variation seen in a large sample of star-burst galaxies in the local Universe. Using multiply lensed images of RCS0327, we probe the same star-forming region at different spatial scales (0.5 kpc\(^2\)-25 kpc\(^2\)), we find that outflow velocities vary between \( \sim \) \(-120\) to \(-242\) km s\(^{-1}\), and the mass outflow rates vary between \(\sim\) 37 to 254 \(M_{\odot}\ yr^{-1}\). The outflow momentum flux in this galaxy is \(\geq\) 100% of the momentum flux provided by star-formation in individual regions, and outflow energy flux is \(\approx\) 10% of the total energy flux provided by star-formation. These estimates suggest that the outflow in RCS0327 is energy driven. This work shows the importance of small scale variations of outflow properties due to the variations of local stellar properties of the host galaxy in the context of galaxy evolution.
We present a pixelized source reconstruction method applied on Integral Field Spectroscopic (IFS) observations of gravitationally lensed galaxies. We demonstrate the effectiveness of this method in a ...case study on the clumpy morphology of a \(z \sim 2\) lensed galaxy behind a group-scale lens. We use a Bayesian forward source modelling approach to reconstruct the surface brightness distribution of the source galaxy on a uniformly pixelized grid while accounting for the image point spread function (PSF). The pixelated approach is sensitive to clump sizes down to 100 pc and resolves smaller clump sizes with an improvement in the signal to noise ratio (SNR) by almost a factor of ten compared with more traditional ray-tracing approaches.
We have selected a sample of 80 candidates for obscured radio-loud active galactic nuclei and presented their basic optical/near-infrared (NIR) properties in Paper 1. In this paper, we present both ...high-resolution radio continuum images for all of these sources and HI 21cm absorption spectroscopy for a few selected sources in this sample. A-configuration 4.9 and 8.5 GHz VLA continuum observations find that 52 sources are compact or have substantial compact components with size <0.5" and flux density >0.1 Jy at 4.9 GHz. The most compact 36 sources were then observed with the VLBA at 1.4 GHz. One definite and 10 candidate Compact Symmetric Objects (CSOs) are newly identified, a detection rate of CSOs ~3 times higher than the detection rate previously found in purely flux-limited samples. Based on possessing compact components with high flux densities, 60 of these sources are good candidates for absorption-line searches. Twenty seven sources were observed for HI 21cm absorption at their photometric or spectroscopic redshifts with only 6 detections made (one detection is tentative). However, five of these were from a small subset of six CSOs with pure galaxy optical/NIR spectra and for which accurate spectroscopic redshifts place the redshifted 21cm line in a RFI-free spectral window. It is likely that the presence of ubiquitous RFI and the absence of accurate spectroscopic redshifts preclude HI detections in similar sources (only one detection out of the remaining 22 sources observed, 14 of which have only photometric redshifts). Future searches for highly-redshifted HI and molecular absorption can easily find more distant CSOs among bright, blank field' radio sources but will be severely hampered by an inability to determine accurate spectroscopic redshifts for them due to their lack of rest-frame UV continuum.
We report an integral-field spectroscopic (IFS) observation of a gravitationally lensed spiral galaxy A1689B11 at redshift \(z=2.54\). It is the most ancient spiral galaxy discovered to date and the ...second kinematically confirmed spiral at \(z\gtrsim2\). Thanks to gravitational lensing, this is also by far the deepest IFS observation with the highest spatial resolution (\(\sim\) 400 pc) on a spiral galaxy at a cosmic time when the Hubble sequence is about to emerge. After correcting for a lensing magnification of 7.2 \(\pm\) 0.8, this primitive spiral disk has an intrinsic star formation rate of 22 \(\pm\) 2 \(M_{\odot}\) yr\(^{-1}\), a stellar mass of 10$^{9.8 \pm 0.3}$$M_{\odot}\( and a half-light radius of \)r_{1/2}=2.6 \pm 0.7\( kpc, typical of a main-sequence star-forming (SF) galaxy at \)z\sim2\(. However, the H\alpha\ kinematics show a surprisingly tranquil velocity field with an ordered rotation (\)V_{\rm c}\( = 200 \)\pm\( 12 km/s) and uniformly small velocity dispersions (\)V_{\rm \sigma, mean}\( = 23 \)\pm\( 4 km/s and \)V_{\rm \sigma, outer-disk}\( = 15 \)\pm\( 2 km/s). The low gas velocity dispersion is similar to local spiral galaxies and is consistent with the classic density wave theory where spiral arms form in dynamically cold and thin disks. We speculate that A1689B11 belongs to a population of rare spiral galaxies at \)z\gtrsim2$ that mark the formation epoch of thin disks. Future observations with JWST will greatly increase the sample of these rare galaxies and unveil the earliest onset of spiral arms.
