16 results on '"de Jong, R. S."'
Search Results
2. Hot Gas Outflow Properties of the Starburst Galaxy NGC 4945.
- Author
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Barrera, Natalia Porraz, Lopez, Sebastian, Lopez, Laura A., Foord, Adi, Nguyen, Dustin D., Thompson, Todd A., Mathur, Smita, and Bolatto, Alberto D.
- Subjects
STARBURSTS ,CHARGE exchange ,X-ray spectra ,X-ray imaging ,GASES - Abstract
We analyze 330 ks of Chandra X-ray imaging and spectra of the nearby, edge-on starburst and Seyfert type 2 galaxy NGC 4945 to measure the hot gas properties along the galactic outflows. We extract and model spectra from 15 regions extending from −0.55 to +0.85 kpc above and below the galactic disk to determine the best-fit parameters and metal abundances. We find that the hot gas temperatures and number densities peak in the central regions and decrease along the outflows. These profiles are inconsistent with a spherical, adiabatically expanding wind model, suggesting the need to include mass loading and/or a nonspherical outflow geometry. We estimate the mass outflow rate of the hot wind to be 1.6 M
⊙ yr−1 . Emission from charge exchange is detected in the northern outflow, and we estimate it contributes 12% to the emitted, broadband (0.5–7 keV) X-ray flux. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
3. Subkiloparsec Scaling Relations between Hot Gas, Dense Gas, and Star Formation Rate in Five Nearby Star-forming Galaxies.
- Author
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Zhang, Chunyi, Wang, Junfeng, Tan, Qing-Hua, Gao, Yu, Lin, Shuting, and Xu, Xiaoyu
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- 2024
- Full Text
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4. Improving Photometric Redshift Estimates with Training Sample Augmentation.
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Moskowitz, Irene, Gawiser, Eric, Crenshaw, John Franklin, Andrews, Brett H., Malz, Alex I., and Schmidt, Samuel
- Published
- 2024
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- View/download PDF
5. An Empirical Calibration of the Tip of the Red Giant Branch Distance Method in the Near Infrared. I. Hubble Space Telescope WFC3/IR F110W and F160W Filters.
- Author
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Newman, Max J. B., McQuinn, Kristen B. W., Skillman, Evan D., Boyer, Martha L., Cohen, Roger E., Dolphin, Andrew E., and Telford, O. Grace
- Subjects
RED giants ,SPACE telescopes ,CALIBRATION ,STELLAR populations ,STARS ,DISTANCES - Abstract
The tip of the red giant branch (TRGB) based distance method in the I band is one of the most efficient and precise techniques for measuring distances to nearby galaxies (D ≲ 15 Mpc). The TRGB in the near-infrared (NIR) is 1–2 mag brighter relative to the I band, and has the potential to expand the range over which distance measurements to nearby galaxies are feasible. Using Hubble Space Telescope (HST) imaging of 12 fields in eight nearby galaxies, we determine color-based corrections and zero-points of the TRGB in the Wide Field Camera 3 IR (WFC3/IR) F110W and F160W filters. First, we measure TRGB distances in the I band equivalent Advanced Camera System (ACS) F814W filter from resolved stellar populations with the HST. The TRGB in the ACS F814W filter is used for our distance anchor and to place the WFC3/IR magnitudes on an absolute scale. We then determine the color dependence (a proxy for metallicity/age) and zero-point of the NIR TRGB from photometry of WFC3/IR fields that overlap with the ACS fields. The new calibration is accurate to ∼1% in distance relative to the F814W TRGB. Validating the accuracy of the calibrations, we find that the distance modulus for each field using the NIR TRGB calibration agrees with the distance modulus of the same field as determined from the F814W TRGB. This is a JWST preparatory program, and the work done here will directly inform our approach to calibrating the TRGB in JWST NIRCam and NIRISS photometric filters. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
6. Evolved Massive Stars at Low Metallicity. VII. The Lower Mass Limit of the Red Supergiant Population in the Large Magellanic Cloud.
- Author
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Yang, Ming, Zhang, Bo, Jiang, Biwei, Gao, Jian, Ren, Yi, Wang, Shu, Lam, Man I, Tian, Hao, Luo, Changqing, Chen, Bingqiu, and Wen, Jing
- Subjects
LARGE magellanic cloud ,ASYMPTOTIC giant branch stars ,SUPERGIANT stars ,RED giants ,STELLAR populations ,ASTROPHYSICS - Abstract
The precise definition of the lower mass limit of red supergiant stars (RSGs) is an open question in astrophysics and does not attract much attention. Here, we assemble a spectroscopic evolved cool star sample with 6602 targets, including RSGs, asymptotic giant branch stars, and red giant branch stars, in the Large Magellanic Cloud based on Gaia DR3 and Sloan Digital Sky Survey IV/APOGEE-2. The reference spectrum of each stellar population is built according to the quantile range of relative intensity (1% ∼ 99%). Five different methods, e.g., χ
2 , cosine similarity, machine learning (ML), equivalent width, and line ratio, are used in order to separate different stellar populations. ML and χ2 provide the best and relatively consistent prediction of a certain population. The derived lower limit of the RSG population is able to reach the Ks -band tip of the red giant branch (Ks ≈12.0 mag), indicating a luminosity as low as about 103.5 L⊙ , which corresponds to a stellar radius of only about 100 R⊙ . Given the mass–luminosity relation of L / L ⊙ = f (M / M ⊙) 3 with f ≈ 15.5 ± 3 and taking into account the mass loss of faint RSGs up to now, the minimal initial mass of the RSG population would be about 6.1 ± 0.4 M⊙ , which is much lower than the traditional threshold of 8 M⊙ for the massive stars. This is the first spectroscopic evidence, indicating that the lower mass limit of the RSG population is around 6 M⊙ . However, the destinies of such faint RSGs are still elusive and may have a large impact on stellar evolutionary and supernova models. [ABSTRACT FROM AUTHOR]- Published
- 2024
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7. Shiva and Shakti: Presumed Proto-Galactic Fragments in the Inner Milky Way.
- Author
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Malhan, Khyati and Rix, Hans-Walter
- Subjects
MILKY Way ,STELLAR mass ,ORBITS (Astronomy) ,DATA release ,ASTROMETRY ,STELLAR orbits - Abstract
Using Gaia Data Release 3 astrometry and spectroscopy, we study two new substructures in the orbit–metallicity space of the inner Milky Way: Shakti and Shiva. They were identified as two confined, high-contrast overdensities in the (L
z , E) distribution of bright (G < 16) and metal-poor (−2.5 < [M/H] < − 1.0) stars. Both have stellar masses of M⋆ ≳ 107 M⊙ , and are distributed on prograde orbits inside the solar circle in the Galaxy. Both structures have an orbit-space distribution that points toward an accreted origin; however, their abundance patterns—from APOGEE—are such that are conventionally attributed to an in situ population. These seemingly contradictory diagnostics could be reconciled if we interpret the abundances [Mg/Fe], [Al/Fe], [Mg/Mn] versus [Fe/H] distribution of their member stars merely as a sign of rapid enrichment. This would then suggest one of two scenarios. Either these prograde substructures were created by some form of resonant orbit trapping of the field stars by the rotating bar; a plausible scenario proposed by Dillamore et al. Or, Shakti and Shiva were protogalactic fragments that formed stars rapidly and coalesced early, akin to the constituents of the poor old heart of the Milky Way, just less deep in the Galactic potential and still discernible in orbit space. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
8. Infrared Radiometric Image Classification and Segmentation of Cloud Structure Using Deep-learning Framework for Ground-based Infrared Thermal Camera Observations.
- Author
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Sommer, Kélian, Kabalan, Wassim, and Brunet, Romain
- Subjects
IMAGE recognition (Computer vision) ,INFRARED imaging ,IMAGE segmentation ,INFRARED cameras ,CONVOLUTIONAL neural networks ,WEATHER ,CLOUDINESS - Abstract
Infrared thermal cameras offer reliable means of assessing atmospheric conditions by measuring the downward radiance from the sky, facilitating their usage in cloud monitoring endeavors. Precise identification and detection of clouds in images pose great challenges stemming from the indistinct boundaries inherent to cloud formations. Various methodologies for segmentation have been previously suggested. Most of them rely on color as the distinguishing criterion for cloud identification in the visible spectral domain and thus lack the ability to detect cloud structure on gray-scaled images with satisfying accuracy. In this work, we propose a new complete deep-learning framework to perform image classification and segmentation with Convolutional Neural Networks. We demonstrate the effectiveness of this technique by conducting a series of tests and validations on self-captured infrared sky images. Our findings reveal that the models can effectively differentiate between image types and accurately capture detailed cloud structure information at the pixel level, even when trained with a single binary ground-truth mask per input sample. The classifier model achieves an excellent accuracy of 99 % in image type distinction, while the segmentation model attains a mean pixel accuracy of 94 % on our dataset. We emphasize that our framework exhibits strong viability and can be used for infrared thermal ground-based cloud monitoring operations over extended durations. We expect to take advantage of this framework for astronomical applications by providing cloud cover selection criteria for ground-based photometric observations within the StarDICE experiment. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
9. ALMA-LEGUS. II. The Influence of Subgalactic Environments on Molecular Cloud Properties.
- Author
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Finn, Molly K., Johnson, Kelsey E., Indebetouw, Remy, Costa, Allison H., Adamo, Angela, Aloisi, Alessandra, Bittle, Lauren, Calzetti, Daniela, Dale, Daniel A., Dobbs, Clare L., Donovan Meyer, Jennifer, Elmegreen, Bruce G., Elmegreen, Debra M., Fumagalli, Michele, Gallagher, J. S., Grasha, Kathryn, Grebel, Eva K., Kennicutt, Robert C., Krumholz, Mark R., and Lee, Janice C.
- Subjects
STAR formation ,GRAVITATIONAL collapse ,INTERSTELLAR medium ,KINETIC energy ,GALAXIES ,MOLECULAR clouds - Abstract
We compare the molecular cloud properties in subgalactic regions of two galaxies, barred spiral NGC 1313, which is forming many massive clusters, and flocculent spiral NGC 7793, which is forming significantly fewer massive clusters despite having a similar star formation rate to NGC 1313. We find that there are larger variations in cloud properties between different regions within each galaxy than there are between the galaxies on a global scale, especially for NGC 1313. There are higher masses, line widths, pressures, and virial parameters in the arms of NGC 1313 and the center of NGC 7793 than in the interarm and outer regions of the galaxies. The massive cluster formation of NGC 1313 may be driven by its greater variation in environment, allowing more clouds with the necessary conditions to emerge, although no one parameter seems primarily responsible for the difference in star formation. Meanwhile NGC 7793 has clouds that are as massive and have as much kinetic energy as the clouds in the arms of NGC 1313, but have densities and pressures more similar to those in the interarm regions and so are less inclined to collapse and form stars. The cloud properties in NGC 1313 and NGC 7793 suggest that spiral arms, bars, interarm regions, and flocculent spirals each represent distinct environments with regard to molecular cloud populations. We see surprisingly little difference in surface density between the regions, suggesting that the differences in surface densities frequently seen between arm and interarm regions in lower-resolution studies are indicative of the sparsity of molecular clouds, rather than differences in their true surface density. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
10. ALMA-LEGUS. I. The Influence of Galaxy Morphology on Molecular Cloud Properties.
- Author
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Finn, Molly K., Johnson, Kelsey E., Indebetouw, Remy, Costa, Allison H., Adamo, Angela, Aloisi, Alessandra, Bittle, Lauren, Calzetti, Daniela, Dale, Daniel A., Dobbs, Clare L., Donovan Meyer, Jennifer, Elmegreen, Bruce G., Elmegreen, Debra M., Fumagalli, Michele, Gallagher, J. S., Grasha, Kathryn, Grebel, Eva K., Kennicutt, Robert C., Krumholz, Mark R., and Lee, Janice C.
- Subjects
MOLECULAR clouds ,GALAXIES ,SUPERGIANT stars ,STAR formation ,STAR clusters ,INTERSTELLAR medium - Abstract
We present a comparative study of the molecular gas in two galaxies from the Legacy ExtraGalactic UV Survey (LEGUS) sample: barred spiral NGC 1313 and flocculent spiral NGC 7793. These two galaxies have similar masses, metallicities, and star formation rates, but NGC 1313 is forming significantly more massive star clusters than NGC 7793, especially young massive clusters (<10 Myr, >10
4 M⊙ ). Using Atacama Large Millimeter/submillimeter Array (ALMA) CO(2–1) observations of the two galaxies with the same sensitivity and resolution (13 pc), we directly compare the molecular gas in these two similar galaxies to determine the physical conditions responsible for their large disparity in cluster formation. By fitting size–line width relations for the clouds in each galaxy, we find that NGC 1313 has a higher intercept than NGC 7793, implying that its clouds have higher kinetic energies at a given size scale. NGC 1313 also has more clouds near virial equilibrium than NGC 7793, which may be connected to its higher rate of massive cluster formation. However, these virially bound clouds do not show a stronger correlation with young clusters than with the general cloud population. We find surprisingly small differences between the distributions of molecular cloud populations in the two galaxies, though the largest of those differences is that NGC 1313 has higher surface densities and lower freefall times. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
11. Comparing the Structural Parameters of the Milky Way to Other Spiral Galaxies.
- Author
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Guerrette, Jacob A., Mosenkov, Aleksandr V., Spencer, Dallin, and Shakespear, Zacory D.
- Published
- 2024
- Full Text
- View/download PDF
12. The Thickness of Galaxy Disks from z = 5 to 0 Probed by JWST.
- Author
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Lian, Jianhui and Luo, Li
- Published
- 2024
- Full Text
- View/download PDF
13. DIISC-III. Signatures of Stellar Disk Growth in Nearby Galaxies.
- Author
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Padave, Mansi, Borthakur, Sanchayeeta, Gim, Hansung B., Thilker, David, Jansen, Rolf A., Monkiewicz, Jacqueline, Kennicutt, Robert C., Kauffmann, Guinevere, Fox, Andrew J., Momjian, Emmanuel, and Heckman, Timothy
- Subjects
INTERSTELLAR medium ,GALAXIES ,GALAXY clusters ,STAR formation ,COLD gases ,DISKS (Astrophysics) ,SPIRAL galaxies - Abstract
We explore the growth of the stellar disks in 14 nearby spiral galaxies as part of the Deciphering the Interplay between the Interstellar medium, Stars, and the Circumgalactic medium (DIISC) survey. We study the radial distribution of specific star formation rates (sSFRs) and investigate the ratio of the difference in the outer and inner sSFRs (Δ
sSFR = sSFRout – sSFRin ) of the disk and the total sSFR, ΔsSFR /sSFR, to quantify disk growth. We find ΔsSFR /sSFR and the H i gas fraction to show a mild correlation of Spearman's ρ = 0.30, indicating that star formation and disk growth are likely to proceed outward in galactic disks with high H i gas fractions. The H i gas fractions and ΔsSFR /sSFR of the galaxies also increase with the distance to the nearest L⋆ neighbor, suggesting that galaxies are likely to sustain the cold gas in their interstellar medium and exhibit inside-out growth in isolated environments. However, the H i content in their circumgalactic medium (CGM), probed by the Ly α equivalent width (WLy α ) excess, is observed to be suppressed in isolated environments, as is apparent from the strong anticorrelation between the WLy α excess and the distance to the fifth nearest L⋆ neighbor (Spearman's ρ = −0.62). As expected, WLy α is also found to be suppressed in cluster galaxies. We find no relation between the WLy α excess of the detected CGM absorber and ΔsSFR /sSFR, implying that the enhancement and suppression of the circumgalactic H i gas does not affect the direction in which star formation proceeds in a galactic disk or vice versa. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
14. Insights into star formation and dispersal from the synchronization of stellar clocks
- Author
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Miret-Roig, Núria, Alves, João, Barrado, David, Burkert, Andreas, Ratzenböck, Sebastian, and Konietzka, Ralf
- Published
- 2024
- Full Text
- View/download PDF
15. Dark Matter And Cosmic Web Story (Second Edition)
- Author
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Jaan Einasto and Jaan Einasto
- Subjects
- Cosmology, Inflationary universe, Astronomers--Estonia--Social conditions--20th century, Dark matter (Astronomy)
- Abstract
The concepts of dark matter and the cosmic web are some of the most significant developments in cosmology in the past century. They have decisively changed the classical cosmological paradigm, which was first elaborated upon during the first half of the 20th century but ran into serious problems in the second half. Today, they are integral parts of modern cosmology, which explains everything from the Big Bang to inflation to the large-scale structure of the Universe.Dark Matter and Cosmic Web Story describes the contributions that led to a paradigm shift from the Eastern point of view. It describes the problems with the classical view, the attempts to solve them, the difficulties encountered by those solutions, and the conferences where the merits of the new concepts were debated. Amidst the science, the story of scientific work in a small country occupied by the Soviet Union and the tumultuous events that led to its breakup are detailed as well.The development of cosmology has often treated as a West-East conflict between the American school led by Jim Peebles in Princeton and the Soviet team led by Yakov Zeldovich in Moscow. Actually, the development of ideas was broader, and a certain role played the Tartu team. The Tartu cosmology school was founded by Ernst Öpik and has its own traditions and attitude to science. In the new edition of the book the interplay between three cosmology schools is written in more detail. The recent development of dark matter and cosmic web studies is described, as well as the evolution of global properties of the cosmic web.This book is accompanied by a website which contains additional material: copies of the originals of some crucial papers, astronomical movies, and movies which showcase the private life of the author. In this second edition, two chapters on the statistical description of the cosmic web and its development were added, as well as chapter on the sociology of science. To keep the length of this book reasonable, a lot of reorganisation of the text has been done as well.
- Published
- 2024
16. Eco-Restoration of Polluted Environment : A Biological Perspective
- Author
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Sandip V. Rathod and Sandip V. Rathod
- Abstract
The book Eco-Restoration of the Polluted Environment: A Biological Perspective explores recent advances in biological strategies for the remediation of polluted environments, including soil, water, and air. It covers bioremediation of heavy metals, radioactive waste, and waste gases, which are believed to be bottleneck problems for researchers working in this field. The book contains separate chapters on genetic engineering technology for enhancement of the bioremediation potential of bioresources and the role of biosurfactants, enzymes, and exo-polysaccharides for bioremediation of polluted environments, along with basic aspects of eco-restoration by microorganisms. It summarizes the significant developments of many years of research in bioremediation technology and discusses them critically by presenting selected examples, while also considering future research directions in the area. Features: Deep insight into the modes of action of various bioremediation strategies, as well as the status and progress of bioremediation technology for sustainable developmental practices A research overview of bioremediation strategies using engineered biological resources for remediation of contaminants. The book will also accelerate the application of suitable engineered microbes and plants for field applications A survey of interdisciplinary findings and insights on the impact of pollution on the ecosystem and human health, climate, and other global changes, with individual solutions to the pollution issue Comprehensive information for relevant stakeholders such as global leaders, agriculturists, investors, innovators, farmers, policymakers, extension workers, agro-industrialists, environmentalists, and the education and health sectors, as well as students and researchers in the field
- Published
- 2024
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