ABSTRACT
We present a pixelized source reconstruction method applied on integral field spectroscopic observations of gravitationally lensed galaxies. We demonstrate the effectiveness of this method ...in a case study on the clumpy morphology of a z ∼ 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. 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 by almost a factor of 10 compared with more traditional ray-tracing approaches.
Spatially resolved studies of high redshift galaxies, particularly in the peak of galaxy formation epoch 1 ≤ z ≤ 3, hold the key for understanding the physics of galaxy formation and evolution. ...Natural magnification provided by gravitational lensing provides a rare opportunity to obtain magnified views of these galaxies at an enhanced spatial resolution. However, lensing has not reached its full potential with traditional source reconstruction approaches because of an under-appreciated problem: source-plane point spread function (PSF).We present a forward modelling approach based on a robust lens model to deconvolve the effects of source-plane PSF and achieve a resolution of ~170 pc in the galaxy-source plane of a z ~ 2 lensed galaxy, which would have been otherwise unachievable through traditional image inversion methods. The forward modelling technique takes full advantage of the lensing amplification by assimilating all the available information from different multiple images of the lensed system. This is crucial in order to confidently analyse the dynamics of the lensed target especially in the low signal to noise (SNR) regions of the image plane. Final merged reconstruction allows a significant improvement (by a factor > 5) in SNR of emission line maps in the source plane. Moreover, different components were detected in the velocity gradient that were not seen in previous studies of this object, plausibly suggesting an ongoing merger in this system.We extend the idea of the forward approach to develop an automated source reconstruction algorithm integrated with a popular lens modelling software, Lenstool. This technique utilizes constraints from the extended surface-brightness profile of the lensed source for a given lens model and reconstructs its intrinsic distribution on a pixelated grid using a bayesian Monte-Carlo Markov chain optimization algorithm in Lenstool. The pixelated source modelling algorithm is validated through the demonstration of different different test simulations. Results from my forward approach are compared against the corresponding traditional reconstructions to measure the effects of PSF smearing on physical sizes of star-forming clumps at high-redshifts.As a first case study, we applied the algorithm to reconstruct the morphology of the same lensed system at z ~2. I obtain a remarkable improvement over traditional ray-tracing, as our technique recovers low surface brightness clumps in the source morphology as a result of PSF deconvolution in the source-plane. There is a factor of 5–10 increase in the SNR of the detected clumps in the source plane using the pixelated approach as compared to those obtained with the traditional reconstruction, especially in the most magnified regions of the source. The results from this case study further motivate the use of pixelized forward modelling technique in future detailed studies of physical properties of lensed galaxies at high resolution using instruments on James Webb Space Telescope (JWST).
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 ∼14.33 and 26.5 kpc, respectively, with maximum spatial extents of ∼21 kpc for Fe ii* emission and ∼30 kpc for Mg ii emission. Mg ii emission is patchy and covers a total area of ∼184 kpc2, constraining the minimum area covered by the outflowing gas to be ∼13% of the total area. Mg ii emission is asymmetric and shows ∼21% more extended emission along the decl. 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 Δv ∼ 400 km s−1. By using multiple images with different magnifications of the galaxy in the image plane, we trace the Fe ii* and 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.
Dissecting a 30 kpc galactic outflow at z ~ 1.7 Shaban, Ahmed; Bordoloi, Rongmon; Chisholm, John ...
Monthly notices of the Royal Astronomical Society,
10/2023, Letnik:
526, Številka:
4
Journal Article
Recenzirano
Odprti dostop
ABSTRACT
We present the spatially resolved measurements of a cool galactic outflow in the gravitationally lensed galaxy RCS0327 at z ≈ 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 – 7 kpc apart within the galaxy, drive the outflows at different velocities (Vout ∼ −161 to −240 km s−1), and mass outflow rates ($\dot{M}_{out} \sim 183$ – 527 ${\rm M}_{\odot }\, \mathrm{yr}^{-1}$). 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 (0.5–25 kpc2), we find that outflow velocities vary between ∼ −120 and −242 km s−1, and the mass outflow rates vary between ∼37 and 254 ${\rm M}_{\odot }\, \mathrm{yr}^{-1}$. The outflow momentum flux in this galaxy is ≥ 100% of the momentum flux provided by star formation in individual regions, and outflow energy flux is ≈ 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.
Abstract
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 of them. We measure a projected cluster core mass of
M
(<250 kpc) =
2.93
−
0.02
+
0.01
×
10
14
M
⊙
. The two least magnified but complete images of the Sunburst Arc’s source galaxy are magnified by ∼13×, while the LyC clump is magnified by ∼4–80×. 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 1 × 2 kpc and that it is resolved in three distinct directions in the source plane, 0°, 40°, and 75° (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.
Our aim was to reveal ultrastructural differences in the endoplasmic reticulum (ER) among surgically removed human pituitary tumors. More than 2000 pituitary tumors were studied by electron ...microscopy. In growth hormone (GH) adenomas, the ER is well developed and consists mainly of rough surfaced endoplasmic reticulum (RER) and few ER membranes without ribosomes, called smooth surfaced endoplasmic reticulum (SER). In the sparsely granulated GH adenomas, the ER is less prominent and is seen in fibrous bodies containing keratin immunopositive microfilaments. In prolactin (PRL) adenomas, the RER is conspicuous, forming concentric whorls. In adenocorticotropin (ACTH) and thyroid stimulating hormone (TSH) adenomas, the ER and consists of RER and to a lesser extent, SER. In gonadotroph adenomas and null cell adenomas, the ER is poorly developed. In GH adenomas exposed to somatostatin analogs and in prolactin adenomas exposed to dopamine agonists, regression of ER is noted. In pituitary carcinomas, the ER is recognizable but it is less extensive than in the benign neoplasms. In conclusion, the ultrastructural investigation of ER provides valuable information on the cytogenesis and cellular composition of pituitary tumors. There is also a mild correlation between endocrine activity and extent of ER. However, no correlation exists between invasive and non‐invasive tumors and growth potential. Pituitary carcinomas cannot be distinguished from benign adenomas based on the ultrastructural features of ER.
Temozolomide, an alkylating imidazotetrazine derivative inhibits DNA replication and is used to treat aggressive brain tumors and other neoplasms including pituitary adenomas. The efficacy of ...temozolomide treatment is dependent on its ability to methylate the O6 position of guanine. The protein MGMT is able to repair this methylation, thus, temozolomide therapy is suggested in patients with little to no MGMT immunopositivity. Three surgically removed pituitary tumors were studied by electron microscopy before and after temozolomide treatment. An MGMT negative aggressive prolactinoma and an oncocytoma with partial MGMT immunopositivity showed tumor shrinkage after temozolomide therapy. A silent ACTH type, with MGMT immunopositivity showed no change in ultrastructure. Electron microscopy of the prolactinoma after temozolomide therapy showed marked destruction and little residual tumor showing no markers of prolactin differentiation. The oncocytoma with partial MGMT immunopositivity showed shrinkage after subsequent temozolomide treatment. The oncocytoma displayed foci of necrosis, likely due to the temozolomide treatment. Our findings suggest that temozolomide acts well on MGMT immunonegative tumor types causing necrosis in tumor tissue. Based on our findings, MGMT can be used as a biomarker for temozolomide therapy, with special attention to the ultrastructural changes in tumor tissue.
Ghrelin, a 28 amino acid‐containing orexigenic peptide, is an endogenous ligand of the GH secretagogue receptor. It was extracted from the rat stomach, but is present in other organs. The aim of this ...work was to localize ghrelin by immunohistochemistry in autopsy‐derived non‐tumorous human pituitaries. Immunohistochemistry was performed using the streptavidin‐biotin‐peroxidase complex method and the results were analyzed independently by 3 of the authors. Double Immunostaining was also undertaken to determine which cell type was expressing both the adenohypophysial hormone and ghrelin.
Results showed that ghrelin can be localized in the adenohypophysis. It's immunoexpression being cytoplasmic, weak to moderate, and present in only a subset of cells. The neurohypophysis is immunonegative. Double immunostaining showed that ghrelin is co‐localized with GH, ACTH and LH and is present to 51–90% of such cells. PRL, TSH and FSH cells are consistently non‐reactive. The role of ghrelin in adenohypophysial endocrine activity is not clear. It may well be that ghrelin exerts an autocrine‐paracrine effect and can modulate hormone synthesis and release.
PDF
