73 research outputs found
Introducing a real-time interactive GUI tool for visualization of galaxy spectra
To aid the understanding of the nonlinear relationship between galaxy properties and predicted spectral energy distributions (SED), we present a new interactive graphical user interface tool pipes_vis based on Bagpipes. It allows for real-time manipulation of a model galaxy's star formation history, dust and other relevant properties through sliders and text boxes, with each change's effect on the predicted SED reflected instantaneously. We hope the tool will assist in building intuition about what affects the SED of galaxies, potentially helping to speed up fitting stages such as prior construction, and aid in undergraduate and graduate teaching. pipes_vis is available online (pipes_vis is maintained and documented online at https://github.com/HinLeung622/pipes_vis, or version 0.4.1 is archived in Zenodo (Leung 2021) and also available for installation through pip install pipes_vis).PostprintNon peer reviewe
Graphical Engine for Android Application Development
Import 05/08/2014Bakalářská práce je zaměřena na problematiku vývoje knihovny určené k tvorbě graficky náročných aplikací pro Android platformu. Dále řeší využití hardwarové akcelerace při vykreslování scény. Animace a transformace mesh objektů. Práci s audio soubory, texturami a shadery. Nastavení a ovládání kamery, či možnost využití fyzikálního enginu. Hlavním cílem práce je tedy vytvoření komplexní knihovny poskytující prostředí pro rychlý a snadný vývoj aplikací.Bachelor thesis is focused on issue of development a library to creating high graphical applications for Android platform. Then solves usage of hardware accelelaration. Animation and transformation of mesh objects. Work with audio files, textures and shaders. Configuration and camera controls or the possibility of using physics engine. The main purpose of this thesis is creation of comprehensive library that provides interface for fast and easy development of aplications.460 - Katedra informatikyvýborn
Chemical evolution of local post-starburst galaxies: Implications for the mass-metallicity relation
We use the stellar fossil record to constrain the stellar metallicity
evolution and star-formation histories of the post-starburst regions within 45
local post-starburst galaxies from the MaNGA survey. The direct measurement of
the regions' stellar metallicity evolution is achieved by a new two-step
metallicity model that allows for stellar metallicity to change at the peak of
the starburst. We also employ a Gaussian process noise model that accounts for
correlated errors introduced by the observational data reduction or
inaccuracies in the models. We find that a majority of post-starburst regions
(69% at significance) increased in stellar metallicity during the
recent starburst, with an average increase of 0.8 dex and a standard deviation
of 0.4 dex. A much smaller fraction of PSBs are found to have remained constant
(22%) or declined in metallicity (9%, average decrease 0.4 dex, standard
deviation 0.3 dex). The pre-burst metallicities of the post-starburst galaxies
are in good agreement with the mass-metallicity relation of local star-forming
galaxies. These results are consistent with hydrodynamic simulations, which
suggest that mergers between gas-rich galaxies are the primary formation
mechanism of local PSBs, and rapid metal recycling during the starburst
outweighs the impact of dilution by any gas inflows. The final mass-weighted
metallicities of the post-starburst galaxies are consistent with the
mass-metallicity relation of local passive galaxies. Our results suggest that
rapid quenching following a merger-driven starburst is entirely consistent with
the observed gap between the stellar mass-metallicity relations of local
star-forming and passive galaxies.Comment: 18+4 pages, 8+2 figures, submitted to MNRA
Chemical evolution of local post-starburst galaxies : implications for the mass-metallicity relation
We use the stellar fossil record to constrain the stellar metallicity evolution and star-formation histories of the post-starburst (PSB) regions within 45 local PSB galaxies from the MaNGA survey. The direct measurement of the regions’ stellar metallicity evolution is achieved by a new two-step metallicity model that allows for stellar metallicity to change at the peak of the starburst. We also employ a Gaussian process noise model that accounts for correlated errors introduced by the observational data reduction or inaccuracies in the models. We find that a majority of PSB regions (69 per cent at >1σ significance) increased in stellar metallicity during the recent starburst, with an average increase of 0.8 dex and a standard deviation of 0.4 dex. A much smaller fraction of PSBs are found to have remained constant (22 per cent) or declined in metallicity (9 per cent, average decrease 0.4 dex, standard deviation 0.3 dex). The pre-burst metallicities of the PSB galaxies are in good agreement with the mass–metallicity (MZ) relation of local star-forming galaxies. These results are consistent with hydrodynamic simulations, which suggest that mergers between gas-rich galaxies are the primary formation mechanism of local PSBs, and rapid metal recycling during the starburst outweighs the impact of dilution by any gas inflows. The final mass-weighted metallicities of the PSB galaxies are consistent with the MZ relation of local passive galaxies. Our results suggest that rapid quenching following a merger-driven starburst is entirely consistent with the observed gap between the stellar mass–metallicity relations of local star-forming and passive galaxies.Peer reviewe
Galaxy mergers can rapidly shut down star formation
Galaxy mergers trigger both star formation and accretion onto the central supermassive black hole. As a result of subsequent energetic feedback processes, it has long been proposed that star formation may be promptly extinguished in galaxy merger remnants. However, this prediction of widespread, rapid quenching in late stage mergers has been recently called into question with modern simulations and has never been tested observationally. Here we perform the first empirical assessment of the long-predicted end phase in the merger sequence. Based on a sample of ~500 post-mergers identified from the Ultraviolet Near Infrared Optical Northern Survey (UNIONS), we show that the frequency of post-merger galaxies that have rapidly shutdown their star formation following a previous starburst is 30-60 times higher than expected from a control sample of non-merging galaxies. No such excess is found in a sample of close galaxy pairs, demonstrating that mergers can indeed lead to a rapid halt to star formation, but that this process only manifests after coalescence.PostprintPeer reviewe
Prognostic impact of TP53 mutations and tumor mutational load in colorectal cancer
The DNA damage response (DDR) is critical for maintaining genome stability, and abnormal DDR—resulting from mutations in DNA damage-sensing and repair proteins—is a hallmark of cancer. Here, we aimed to investigate the predictive power of DDR gene mutations and the tumor mutational load (TML) for survival outcomes in a cohort of 22 rectal cancer patients who received pre-operative neoadjuvant therapy. Univariate analysis revealed that TML-high and TP53 mutations were significantly associated with worse overall survival (OS) with TML-high retaining significance in multivariate analyses. Kaplan–Meier survival analyses further showed TML-high was associated with worse disease-free (p = 0.036) and OS (p = 0.024) results in our patient cohort. A total of 53 somatic mutations were identified in 22 samples with eight (36%) containing mutations in DDR genes, including ATM, ATR, CHEK2, MRE11A, RAD50, NBN, ERCC2 and TP53. TP53 was the most frequently mutated gene, and TP53 mutations were significantly associated with worse OS (p = 0.023) in Kaplan–Meier survival analyses. Thus, our data indicate that TML and TP53 mutations have prognostic value for rectal cancer patients and may be important independent biomarkers for patient management. This suggests that prognostic determination for rectal cancer patients receiving pre-operative neoadjuvant therapy should include consideration of the initial TML and tumor genetic status
Optical vs. infrared studies of dusty galaxies and AGN: (I) Nebular emission lines
Optical nebular emission lines are commonly used to estimate the star
formation rate of galaxies and the black hole accretion rate of their central
active nucleus. The accuracy of the conversion from line strengths to physical
properties depends upon the accuracy to which the lines can be corrected for
dust attenuation. For studies of single galaxies with normal amounts of dust,
most dust corrections result in the same derived properties within the errors.
However, for statistical studies of populations of galaxies, or for studies of
galaxies with higher dust contents such as might be found in some classes of
"transition" galaxies, significant uncertainty arises from the dust attenuation
correction. We compare the strength of the predominantly unobscured mid-IR
[NeII]15.5um + [NeIII]12.8um emission lines to the optical H alpha emission
lines in four samples of galaxies: (i) ordinary star forming galaxies, (ii)
optically selected dusty galaxies, (iii) ULIRGs, (iv) Seyfert 2 galaxies. We
show that a single dust attenuation curve applied to all samples can correct H
alpha emission for dust attenuation to a factor better than 2. Similarly, we
compare mid-IR [OIV] and optical [OIII] luminosities to find that [OIII] can be
corrected to a factor better than 3. This shows that the total dust attenuation
suffered by the AGN narrow line region is not significantly different to that
suffered by the starforming HII regions in the galaxy. We provide explicit dust
attenuation corrections, together with errors, for [OII], [OIII] and H alpha.
The best-fit average attenuation curve is slightly greyer than the Milky-Way
extinction law, indicating either that external galaxies have slightly
different typical dust properties to the Milky Way, or that there is a
significant contribution from scattering. Finally, we uncover an intriguing
correlation between Silicate absorption and Balmer decrement.Comment: 19 pages, 9 figures, accepted for publication in MNRA
The Fourteenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the extended Baryon Oscillation Spectroscopic Survey and from the second phase of the Apache Point Observatory Galactic Evolution Experiment
The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) has been in
operation since July 2014. This paper describes the second data release from
this phase, and the fourteenth from SDSS overall (making this, Data Release
Fourteen or DR14). This release makes public data taken by SDSS-IV in its first
two years of operation (July 2014-2016). Like all previous SDSS releases, DR14
is cumulative, including the most recent reductions and calibrations of all
data taken by SDSS since the first phase began operations in 2000. New in DR14
is the first public release of data from the extended Baryon Oscillation
Spectroscopic Survey (eBOSS); the first data from the second phase of the
Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE-2),
including stellar parameter estimates from an innovative data driven machine
learning algorithm known as "The Cannon"; and almost twice as many data cubes
from the Mapping Nearby Galaxies at APO (MaNGA) survey as were in the previous
release (N = 2812 in total). This paper describes the location and format of
the publicly available data from SDSS-IV surveys. We provide references to the
important technical papers describing how these data have been taken (both
targeting and observation details) and processed for scientific use. The SDSS
website (www.sdss.org) has been updated for this release, and provides links to
data downloads, as well as tutorials and examples of data use. SDSS-IV is
planning to continue to collect astronomical data until 2020, and will be
followed by SDSS-V.Comment: SDSS-IV collaboration alphabetical author data release paper. DR14
happened on 31st July 2017. 19 pages, 5 figures. Accepted by ApJS on 28th Nov
2017 (this is the "post-print" and "post-proofs" version; minor corrections
only from v1, and most of errors found in proofs corrected
The 13th Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-IV Survey Mapping Nearby Galaxies at Apache Point Observatory
The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) began observations in July 2014. It pursues three core programs: APOGEE-2,MaNGA, and eBOSS. In addition, eBOSS contains two major subprograms: TDSS and SPIDERS. This paper describes the first data release from SDSS-IV, Data Release 13 (DR13), which contains new data, reanalysis of existing data sets and, like all SDSS data releases, is inclusive of previously released data. DR13 makes publicly available 1390 spatially resolved integral field unit observations of nearby galaxies from MaNGA,the first data released from this survey. It includes new observations from eBOSS, completing SEQUELS. In addition to targeting galaxies and quasars, SEQUELS also targeted variability-selected objects from TDSS and X-ray selected objects from SPIDERS. DR13 includes new reductions ofthe SDSS-III BOSS data, improving the spectrophotometric calibration and redshift classification. DR13 releases new reductions of the APOGEE-1data from SDSS-III, with abundances of elements not previously included and improved stellar parameters for dwarf stars and cooler stars. For the SDSS imaging data, DR13 provides new, more robust and precise photometric calibrations. Several value-added catalogs are being released in tandem with DR13, in particular target catalogs relevant for eBOSS, TDSS, and SPIDERS, and an updated red-clump catalog for APOGEE.This paper describes the location and format of the data now publicly available, as well as providing references to the important technical papers that describe the targeting, observing, and data reduction. The SDSS website, http://www.sdss.org, provides links to the data, tutorials and examples of data access, and extensive documentation of the reduction and analysis procedures. DR13 is the first of a scheduled set that will contain new data and analyses from the planned ~6-year operations of SDSS-IV.PostprintPeer reviewe
Sloan Digital Sky Survey IV: mapping the Milky Way, nearby galaxies, and the distant universe
We describe the Sloan Digital Sky Survey IV (SDSS-IV), a project encompassing three major spectroscopic programs. The Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2) is observing hundreds of thousands of Milky Way stars at high resolution and high signal-to-noise ratios in the near-infrared. The Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey is obtaining spatially resolved spectroscopy for thousands of nearby galaxies (median ). The extended Baryon Oscillation Spectroscopic Survey (eBOSS) is mapping the galaxy, quasar, and neutral gas distributions between and 3.5 to constrain cosmology using baryon acoustic oscillations, redshift space distortions, and the shape of the power spectrum. Within eBOSS, we are conducting two major subprograms: the SPectroscopic IDentification of eROSITA Sources (SPIDERS), investigating X-ray AGNs and galaxies in X-ray clusters, and the Time Domain Spectroscopic Survey (TDSS), obtaining spectra of variable sources. All programs use the 2.5 m Sloan Foundation Telescope at the Apache Point Observatory; observations there began in Summer 2014. APOGEE-2 also operates a second near-infrared spectrograph at the 2.5 m du Pont Telescope at Las Campanas Observatory, with observations beginning in early 2017. Observations at both facilities are scheduled to continue through 2020. In keeping with previous SDSS policy, SDSS-IV provides regularly scheduled public data releases; the first one, Data Release 13, was made available in 2016 July
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