| 1. |
- Ashcraft, Teresa A., et al.
(författare)
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Ultra-deep Large Binocular Camera U-band Imaging of the GOODS-North Field : Depth Versus Resolution
- 2018
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Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 130:988
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Tidskriftsartikel (refereegranskat)abstract
- We present a study of the trade-off between depth and resolution using a large number of U-band imaging observations in the GOODS-North field from the Large Binocular Camera (LBC) on the Large Binocular Telescope (LBT). Having acquired over 30 hr of data (315 images with 5-6 minutes exposures), we generated multiple image mosaics, starting with the best atmospheric seeing images (FWHM less than or similar to 0 ''.8), which constitute similar to 10% of the total data set. For subsequent mosaics, we added in data with larger seeing values until the final, deepest mosaic included all images with FWHM less than or similar to 1 ''.8 (similar to 94% of the total data set). From the mosaics, we made object catalogs to compare the optimal-resolution, yet shallower image to the lower-resolution but deeper image. We show that the number counts for both images are similar to 90% complete to U-AB less than or similar to 26 mag. Fainter than U-AB similar to 27 mag, the object counts from the optimal-resolution image start to drop-off dramatically (90% between U-AB = 27 and 28 mag), while the deepest image with better surface-brightness sensitivity (mu(AB)(U) less than or similar to 32 mag arcsec(-2)) show a more gradual drop (10% between U-AB similar or equal to 27 and 28 mag). For the brightest galaxies within the GOODS-N field, structure and clumpy features within the galaxies are more prominent in the optimal-resolution image compared to the deeper mosaics. We conclude that for studies of brighter galaxies and features within them, the optimal-resolution image should be used. However, to fully explore and understand the faintest objects, the deeper imaging with lower resolution are also required. Finally, we find-for 220 brighter galaxies with U-AB less than or similar to 23 mag-only marginal differences in total flux between the optimal-resolution and lower-resolution light-profiles to mu(AB)(U) less than or similar to 32 mag arcsec(-2). In only 10% of the cases are the total-flux differences larger than 0.5 mag. This helps constrain how much flux can be missed from galaxy outskirts, which is important for studies of the Extragalactic Background Light.
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| 2. |
- Diego, Jose M., et al.
(författare)
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JWST's PEARLS : Mothra, a new kaiju star at z=2.091 extremely magnified by MACS0416, and implications for dark matter models
- 2023
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 679
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Tidskriftsartikel (refereegranskat)abstract
- We report the discovery of Mothra, an extremely magnified monster star, likely a binary system of two supergiant stars, in one of the strongly lensed galaxies behind the galaxy cluster MACS J0416.1-2403. Mothra is in a galaxy with spectroscopic redshift z = 2.091 in a portion of the galaxy that is parsecs away from the cluster caustic. The binary star is observed only on the side of the critical curve with negative parity but has been detectable for at least eight years, implying the presence of a small lensing perturber. Microlenses alone cannot explain the earlier observations of this object made with the Hubble Space Telescope. A larger perturber with a mass of at least 10(4 )M(circle dot) offers a more satisfactory explanation. Based on the lack of perturbation on other nearby sources in the same arc, the maximum mass of the perturber is 2.5 x 10(6) M-circle dot, making this the smallest substructure constrained by lensing at z > 0.3. The existence of this millilens is fully consistent with expectations from standard cold dark matter cosmology. On the other hand, the existence of such a small substructure in a cluster environment has implications for other dark matter models. In particular, warm dark matter models with particle masses below 8.7 keV are excluded by our observations. Similarly, axion dark matter models are consistent with the observations only if the axion mass is in the range 0.5 x 10(-22) eV < m(a )< 5 x 10(-22) eV.
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| 3. |
- Ferreras, Ignacio, et al.
(författare)
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FIGS : spectral fitting constraints on the star formation history of massive galaxies since the cosmic noon
- 2019
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 486:1, s. 1358-1376
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Tidskriftsartikel (refereegranskat)abstract
- We constrain the stellar population properties of a sample of 52 massive galaxies - with stellar mass log (M-s/M-circle dot) greater than or similar to 10.5 - over the redshift range 0.5 < z < 2 by use of observer-frame optical and near-infrared slitless spectra from Hubble Space Telescope's ACS and WFC3 grisms. The deep exposures (similar to 100 ks) allow us to target individual spectra of massive galaxies to F160W = 22.5AB. Our spectral fitting approach uses a set of six base models adapted to the redshift and spectral resolution of each observation, and fits the weights of the base models, including potential dust attenuation, via a Markov Chain Monte Carlo method. Our sample comprises a mixed distribution of quiescent (19) and star-forming galaxies (33). We quantify the width of the age distribution (Delta t) that is found to dominate the variance of the retrieved parameters according to principal component analysis. The population parameters follow the expected trend towards older ages with increasing mass, and Delta t appears to weakly anticorrelate with stellar mass, suggesting a more efficient star formation at the massive end. As expected, the redshift dependence of the relative stellar age (measured in units of the age of the Universe at the source) in the quiescent sample rejects the hypothesis of a single burst (aka monolithic collapse). Radial colour gradients within each galaxy are also explored, finding a wider scatter in the star-forming subsample, but no conclusive trend with respect to the population parameters.
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| 4. |
- Fudamoto, Yoshinobu, et al.
(författare)
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The Extended [C II] under Construction? : Observation of the Brightest High-z Lensed Star-forming Galaxy at z=6.2
- 2024
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Ingår i: Astrophysical Journal. - : Institute of Physics Publishing (IOPP). - 0004-637X .- 1538-4357. ; 961:1
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Tidskriftsartikel (refereegranskat)abstract
- We present results of [C ii] 158 μm emission line observations, and report the spectroscopic redshift confirmation of a strongly lensed (μ ∼ 20) star-forming galaxy, MACS0308-zD1 at z = 6.2078 ± 0.0002. The [C ii] emission line is detected with a signal-to-noise ratio >6 within the rest-frame UV-bright clump of the lensed galaxy (zD1.1) and exhibits multiple velocity components; the narrow [C ii] has a velocity full width half maximum (FWHM) of 110 ± 20 km s−1, while broader [C ii] is seen with an FWHM of 230 ± 50 km s−1. The broader [C ii] component is blueshifted (−80 ± 20 km s−1) with respect to the narrow [C ii] component, and has a morphology that extends beyond the UV-bright clump. We find that, while the narrow [C ii] emission is most likely associated with zD1.1, the broader component is possibly associated with a physically distinct gas component from zD1.1 (e.g., outflowing or inflowing gas). Based on the nondetection of λ158μm dust continuum, we find that MACS0308-zD1's star formation activity occurs in a dust-free environment indicated by a strong upper limit of infrared luminosity ≲9 × 108L⊙. Targeting this strongly lensed faint galaxy for follow-up Atacama Large Millimeter/submillimeter Array and JWST observations will be crucial to characterize the details of typical galaxy growth in the early Universe.
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| 5. |
- Hsiao, Tiger Yu-Yang, et al.
(författare)
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JWST Reveals a Possible z similar to 11 Galaxy Merger in Triply Lensed MACS0647-JD
- 2023
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8205 .- 2041-8213. ; 949:2
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Tidskriftsartikel (refereegranskat)abstract
- MACS0647-JD is a triply lensed z similar to 11 galaxy originally discovered with the Hubble Space Telescope. The three lensed images are magnified by factors of similar to 8, 5, and 2 to AB mag 25.1, 25.6, and 26.6 at 3.5 mu m. The brightest is over a magnitude brighter than other galaxies recently discovered at similar redshifts z > 10 with JWST. Here, we report new JWST imaging that clearly resolves MACS0647-JD as having two components that are either merging galaxies or stellar complexes within a single galaxy. The brighter larger component "A" is intrinsically very blue (ss similar to-2.6 +/- 0.1), likely due to very recent star formation and no dust, and is spatially extended with an effective radius similar to 70 +/- 24 pc. The smaller component "B" (r similar to 20-+ 58 pc) appears redder (ss similar to-2 +/- 0.2), likely because it is older (100-200 Myr) with mild dust extinction (AV similar to 0.1 mag). With an estimated stellar mass ratio of roughly 2:1 and physical projected separation similar to 400 pc, we may be witnessing a galaxy merger 430 million years after the Big Bang. We identify galaxies with similar colors in a high-redshift simulation, finding their star formation histories to be dissimilar, which is also suggested by the spectral energy distribution fitting, suggesting they formed further apart. We also identify a candidate companion galaxy "C" similar to 3 kpc away, likely destined to merge with A and B. Upcoming JWST Near Infrared Spectrograph observations planned for 2023 January will deliver spectroscopic redshifts and more physical properties for these tiny magnified distant galaxies observed in the early universe.
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| 6. |
- Kuschel, Maxwell, et al.
(författare)
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Investigating the Dominant Environmental Quenching Process in UVCANDELS/COSMOS Groups
- 2023
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 947:1
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Tidskriftsartikel (refereegranskat)abstract
- We explore how the fraction of quenched galaxies changes in groups of galaxies with respect to the distance to the center of the group, redshift, and stellar mass to determine the dominant process of environmental quenching in 0.2 < z < 0.8 groups. We use new UV data from the UVCANDELS project in addition to existing multiband photometry to derive new galaxy physical properties of the group galaxies from the zCOSMOS 20 k group catalog. Limiting our analysis to a complete sample of log (M*/M⊙) > 10.56 group galaxies, we find that the probability of being quenched increases slowly with decreasing redshift, diverging from the stagnant field galaxy population. A corresponding analysis on how the probability of being quenched increases with time within groups suggests that the dominant environmental quenching process is characterized by slow (∼Gyr) timescales. We find a quenching time of approximately Gyr, consistent with the slow processes of strangulation and delayed-then-rapid quenching although more data are needed to confirm this result.
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| 7. |
- Larson, Rebecca L., et al.
(författare)
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Discovery of a z=7.452 High Equivalent Width Ly alpha Emitter from the Hubble Space Telescope Faint Infrared Grism Survey
- 2018
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 858:2
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Tidskriftsartikel (refereegranskat)abstract
- We present the results of an unbiased search for Ly alpha emission from continuum-selected 5.6 < z < 8.7 galaxies. Our data set consists of 160 orbits of G102 slitless grism spectroscopy obtained with the Hubble Space Telescope (HST)/WFC3 as part of the Faint Infrared Grism Survey (FIGS; PI: Malhotra), which obtains deep slitless spectra of all sources in four fields, and was designed to minimize contamination in observations of previously identified high-redshift galaxy candidates. The FIGS data can potentially spectroscopically confirm the redshifts of galaxies, and as Ly alpha emission is resonantly scattered by neutral gas, FIGS can also constrain the ionization state of the intergalactic medium during the epoch of reionization. These data have sufficient depth to detect Ly alpha emission in this epoch, as Tilvi et al. have published the FIGS detection of previously known Ly alpha emission at z = 7.51. The FIGS data use five separate roll angles of HST to mitigate the contamination by nearby galaxies. We created a method that accounts for and removes the contamination from surrounding galaxies and also removes any dispersed continuum light from each individual spectrum. We searched for significant (>4 sigma) emission lines using two different automated detection methods, free of any visual inspection biases. Applying these methods on photometrically selected high-redshift candidates between 5.6 < z < 8.7, we find two emission lines, one previously published by Tilvi et al., (2016) and a new line at 1.028 mu m, which we identify as Ly alpha at z = 7.452 +/- 0.003. This newly spectroscopically confirmed galaxy has the highest Ly alpha rest-frame equivalent width (EWLy alpha) yet published at z > 7 (140.3 +/- 19.0 ångström).
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| 8. |
- Martin, Alec, et al.
(författare)
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UV-bright Star-forming Clumps and Their Host Galaxies in UVCANDELS at 0.5 ≤ z ≤ 1
- 2023
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 955:2
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Tidskriftsartikel (refereegranskat)abstract
- Giant star-forming clumps are a prominent feature of star-forming galaxies (SFGs) and contain important clues on galaxy formation and evolution. However, the basic demographics of clumps and their host galaxies remain uncertain. Using the Hubble Space Telescope/Wide Field Camera 3 F275W images from the Ultraviolet Imaging of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, we detect and analyze giant star-forming clumps in galaxies at 0.5 ≤ z ≤ 1, connecting two epochs when clumps are common (at cosmic high noon, z ∼ 2) and rare (in the local Universe). We construct a clump sample whose rest-frame 1600 Å luminosity is 3 times higher than the most luminous local H ii regions (MUV ≤ −16 AB). In our sample, 35% ± 3% of low-mass galaxies (log[M∗/M⊙] < 10) are clumpy (i.e., containing at least one off-center clump). This fraction changes to 22% ± 3% and 22% ± 4% for intermediate (10 ≤ log[M∗/M⊙] ≤ 10.5) and high-mass (log[M∗/M⊙] > 10.5) galaxies, in agreement with previous studies. When compared to similar-mass nonclumpy SFGs, low- and intermediate-mass clumpy SFGs tend to have higher star formation rates (SFRs) and bluer rest-frame U − V colors, while high-mass clumpy SFGs tend to be larger than nonclumpy SFGs. However, clumpy and nonclumpy SFGs have similar Sérsic index, indicating a similar underlying density profile. Furthermore, we investigate how the UV luminosity of star-forming regions correlates with the physical properties of host galaxies. On average, more luminous star-forming regions reside in more luminous, smaller, and/or higher specific SFR galaxies and are found closer to their hosts' galactic centers.
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| 9. |
- Meena, Ashish Kumar, et al.
(författare)
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Two Lensed Star Candidates at z similar or equal to 4.8 behind the Galaxy Cluster MACS J0647.7+7015
- 2023
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Ingår i: Astrophysical Journal Letters. - : Institute of Physics (IOP). - 2041-8205 .- 2041-8213. ; 944:1
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Tidskriftsartikel (refereegranskat)abstract
- We report the discovery of two extremely magnified lensed star candidates behind the galaxy cluster MACS J0647.7+015 using recent multiband James Webb Space Telescope (JWST) NIRCam observations. The star candidates are seen in a previously known, z (phot) similar or equal to 4.8 dropout giant arc that straddles the critical curve. The candidates lie near the expected critical curve position, but lack clear counter-images on the other side of it, suggesting these are possibly stars undergoing caustic crossings. We present revised lensing models for the cluster, including multiply imaged galaxies newly identified in the JWST data, and use them to estimate background macro-magnifications of at least greater than or similar to 90 and greater than or similar to 50 at the positions of the two candidates, respectively. With these values, we expect effective, caustic-crossing magnifications of similar to[10(3)-10(5)] for the two star candidates. The spectral energy distributions of the two candidates match well the spectra of B-type stars with best-fit surface temperatures of similar to 10,000 K, and similar to 12,000 K, respectively, and we show that such stars with masses greater than or similar to 20 M (circle dot) and greater than or similar to 50 M (circle dot), respectively, can become sufficiently magnified to be observable. We briefly discuss other alternative explanations and conclude that these objects are likely lensed stars, but also acknowledge that the less-magnified candidate may alternatively reside in a star cluster. These star candidates constitute the second highest-redshift examples to date after Earendel at z (phot) similar or equal to 6.2, establishing further the potential of studying extremely magnified stars at high redshifts with JWST. Planned future observations, including with NIRSpec, will enable a more detailed view of these candidates in the near future.
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| 10. |
- Meena, Ashish Kumar, et al.
(författare)
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Two Lensed Star Candidates at z ≃ 4.8 behind the Galaxy Cluster MACS J0647.7+7015
- 2023
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8205 .- 2041-8213. ; 944:1
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Tidskriftsartikel (refereegranskat)abstract
- We report the discovery of two extremely magnified lensed star candidates behind the galaxy cluster MACS J0647.7+015 using recent multiband James Webb Space Telescope (JWST) NIRCam observations. The star candidates are seen in a previously known, zphot ≃ 4.8 dropout giant arc that straddles the critical curve. The candidates lie near the expected critical curve position, but lack clear counter-images on the other side of it, suggesting these are possibly stars undergoing caustic crossings. We present revised lensing models for the cluster, including multiply imaged galaxies newly identified in the JWST data, and use them to estimate background macro-magnifications of at least ≳90 and ≳50 at the positions of the two candidates, respectively. With these values, we expect effective, caustic-crossing magnifications of ∼[103–105] for the two star candidates. The spectral energy distributions of the two candidates match well the spectra of B-type stars with best-fit surface temperatures of ∼10,000 K, and ∼12,000 K, respectively, and we show that such stars with masses ≳20 M⊙ and ≳50 M⊙, respectively, can become sufficiently magnified to be observable. We briefly discuss other alternative explanations and conclude that these objects are likely lensed stars, but also acknowledge that the less-magnified candidate may alternatively reside in a star cluster. These star candidates constitute the second highest-redshift examples to date after Earendel at zphot ≃ 6.2, establishing further the potential of studying extremely magnified stars at high redshifts with JWST. Planned future observations, including with NIRSpec, will enable a more detailed view of these candidates in the near future.
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