Central velocity dispersion catalogue of LAMOST-DR7 galaxies

ABSTRACT The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) is a major facility to carry out spectroscopic surveys for cosmology and galaxy evolution studies. The seventh data release of the LAMOST ExtraGAlactic Survey (LEGAS) is currently available and including redshifts of 193 361 galaxies. These sources are spread over $\sim 11\, 500$ deg2 of the sky, largely overlapping with other imaging (SDSS and HSC) and spectroscopic (BOSS) surveys. The estimated depth of the galaxy sample, r ∼ 17.8, the high signal-to-noise ratio, and the spectral resolution R = 1800, make the LAMOST spectra suitable for galaxy velocity dispersion (VD) measurements, which are invaluable to study the structure and formation of galaxies and to determine their central dark matter content. We present the first estimates of central VD of $\sim 86\, 000$ galaxies in LAMOST footprint. We have used a wrap-up procedure to perform the spectral fitting using ppxf, and derive VD measurements. Statistical errors are also assessed by comparing LAMOST VD estimates with the ones of SDSS and BOSS over a common sample of $\sim 51\, 000$ galaxies. The two data sets show a good agreement, within the statistical errors, in particular when VD values are corrected to 1 effective radius aperture. We also present a preliminary mass–σ relation and find consistency with previous analyses based on local galaxy samples. These first results suggest that LAMOST spectra are suitable for galaxy VD measurements to complement the available catalogues of galaxy internal kinematics in the Northern hemisphere. We plan to expand this analysis to next LAMOST data releases.

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GALEX absolute calibration and extinction coefficients based on white dwarfs

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2506 ◽

2019 ◽

Vol 489 (4) ◽

pp. 5046-5052 ◽

Cited By ~ 1

Author(s):

Renae E Wall ◽

Mukremin Kilic ◽

P Bergeron ◽

B Rolland ◽

C Genest-Beaulieu ◽

...

Keyword(s):

Galaxy Evolution ◽

White Dwarfs ◽

Signal To Noise Ratio ◽

Model Atmosphere ◽

Absolute Calibration ◽

High Signal ◽

Extinction Coefficients ◽

Near Ultraviolet ◽

The Galaxy ◽

Far Ultraviolet

ABSTRACT We use 1837 DA white dwarfs with high signal-to-noise ratio spectra and Gaia parallaxes to verify the absolute calibration and extinction coefficients for the Galaxy Evolution Explorer (GALEX). We use white dwarfs within 100 pc to verify the linearity correction to the GALEX data. We find that the linearity correction is valid for magnitudes brighter than 15.95 and 16.95 for the far-ultraviolet (FUV) and near-ultraviolet (NUV) bands, respectively. We also use DA white dwarfs beyond 250 pc to calculate extinction coefficients in the FUV and NUV bands: RFUV = 8.01 ± 0.07 and RNUV = 6.72 ± 0.04. These are consistent with the predicted extinction coefficients for Milky Way-type dust in the FUV, but smaller than predictions in the NUV. With well understood optical spectra and state-of-the-art model atmosphere analysis, these white dwarfs currently provide the best constraints on the extinction coefficients for the GALEX data.

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Autonomous Gaussian decomposition of the Galactic Ring Survey

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936814 ◽

2019 ◽

Vol 633 ◽

pp. A14 ◽

Cited By ~ 5

Author(s):

M. Riener ◽

J. Kainulainen ◽

H. Beuther ◽

J. D. Henshaw ◽

J. H. Orkisz ◽

...

Keyword(s):

Velocity Dispersion ◽

Velocity Structure ◽

Galactic Plane ◽

Emission Lines ◽

Data Sets ◽

Gas Kinematics ◽

The Galaxy ◽

First Results ◽

Physical Information ◽

Gaussian Decomposition

The analysis of large molecular line surveys of the Galactic plane is essential for our understanding of the gas kinematics on Galactic scales and, in particular, its link with the formation and evolution of dense structures in the interstellar medium. An approximation of the emission peaks with Gaussian functions allows for an efficient and straightforward extraction of useful physical information contained in the shape and Doppler-shifted frequency of the emission lines contained in these enormous data sets. In this work, we present an overview and the first results of a Gaussian decomposition of the entire Galactic Ring Survey (GRS) 13CO (1–0) data that consists of about 2.3 million spectra. We performed the decomposition with the fully automated GAUSSPY+ algorithm and fitted about 4.6 million Gaussian components to the GRS spectra. These decomposition results enable novel and unexplored ways to interpret and study the gas velocity structure. We discuss the statistics of the fit components and relations between the fitted intensities, velocity centroids, and velocity dispersions. We find that the magnitude of the velocity dispersion values increase towards the inner Galaxy and around the Galactic midplane, which we speculate is partly due to the influence of the Galactic bar and regions with higher non-thermal motions located in the midplane, respectively. We also used our decomposition results to infer global properties of the gas emission and find that the number of fit components used per spectrum is indicative of the amount of structure along the line of sight. We find that the emission lines from regions located on the far side of the Galaxy show increased velocity dispersion values, which are likely due to beam averaging effects. We demonstrate how this trend has the potential to aid in characterising Galactic structure by disentangling emission that belongs to the nearby Aquila Rift molecular cloud from emission that is more likely associated with the Perseus and Outer spiral arms. With this work, we also make our entire decomposition results available.

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Galaxy properties as revealed by MaNGA – III. Kinematic profiles and stellar population gradients in S0s

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1364 ◽

2020 ◽

Vol 495 (3) ◽

pp. 2894-2908 ◽

Cited By ~ 3

Author(s):

H Domínguez Sánchez ◽

M Bernardi ◽

F Nikakhtar ◽

B Margalef-Bentabol ◽

R K Sheth

Keyword(s):

Stellar Population ◽

Velocity Dispersion ◽

Signal To Noise Ratio ◽

Elliptical Galaxies ◽

Element Abundance ◽

High Signal ◽

Galactocentric Distance ◽

Massive Galaxies ◽

Nearby Galaxies ◽

Mass Functions

ABSTRACT This is the third paper of a series where we study the stellar population gradients (SP; ages, metallicities, α-element abundance ratios, and stellar initial mass functions) of early-type galaxies (ETGs) at $z$ ≤ 0.08 from the Mapping Nearby Galaxies at APO Data Release 15 (MaNGA-DR15) survey. In this work, we focus on the S0 population and quantify how the SP varies across the population as well as with galactocentric distance. We do this by measuring Lick indices and comparing them to SP synthesis models. This requires spectra with high signal-to-noise ratio which we achieve by stacking in bins of luminosity (Lr) and central velocity dispersion (σ0). We find that: (1) there is a bimodality in the S0 population: S0s more massive than $3\times 10^{10}\, \mathrm{M}_\odot$ show stronger velocity dispersion and age gradients (age and σr decrease outwards) but little or no metallicity gradient, while the less massive ones present relatively flat age and velocity dispersion profiles, but a significant metallicity gradient (i.e. [M/H] decreases outwards). Above $2\times 10^{11}\, \mathrm{M}_\odot$, the number of S0s drops sharply. These two mass scales are also where global scaling relations of ETGs change slope. (2) S0s have steeper velocity dispersion profiles than fast-rotating elliptical galaxies (E-FRs) of the same luminosity and velocity dispersion. The kinematic profiles and SP gradients of E-FRs are both more similar to those of slow-rotating ellipticals (E-SRs) than to S0s, suggesting that E-FRs are not simply S0s viewed face-on. (3) At fixed σ0, more luminous S0s and E-FRs are younger, more metal rich and less α-enhanced. Evidently for these galaxies, the usual statement that ‘massive galaxies are older’ is not true if σ0 is held fixed.

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Poor Groups Around Strong Gravitational Lenses

Proceedings of the International Astronomical Union ◽

10.1017/s174392130600634x ◽

2006 ◽

Vol 2 (S235) ◽

pp. 230-230

Author(s):

Ivelina Momcheva ◽

Kurtis Williams ◽

Ann Zabludoff ◽

Charles Keeton

Keyword(s):

Galaxy Evolution ◽

Velocity Dispersion ◽

Gravitational Lenses ◽

Local Universe ◽

Groups Of Galaxies ◽

Hot Gas ◽

Gas Kinematics ◽

The Galaxy ◽

Group Centroid ◽

Group Galaxy

AbstractPoor groups are common and interactive environments for galaxies, and thus are important laboratories for studying galaxy evolution. Unfortunately, little is known about groups at z ≥ 0.1, because of the difficulty in identifying them in the first place. Here we present results from our ongoing survey of the environments of strong gravitational lenses, in which we have so far discovered six distant (z ≥ 0.5) groups of galaxies. As in the local Universe, the highest velocity dispersion groups contain a brightest member spatially coincident with the group centroid, whereas lower-dispersion groups tend to have an offset brightest group galaxy. This suggests that higher-dispersion groups are more dynamically relaxed than lower-dispersion groups and that at least some evolved groups exist by z ~ 0.5. We also compare the galaxy and hot gas kinematics with those of similarly distant clusters and of nearby groups.

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Assisted traveltime picking of crosshole GPR data

Geophysics ◽

10.1190/1.3141002 ◽

2009 ◽

Vol 74 (4) ◽

pp. J35-J48 ◽

Cited By ~ 9

Author(s):

Bernard Giroux ◽

Abderrezak Bouchedda ◽

Michel Chouteau

Keyword(s):

Time Window ◽

Signal To Noise Ratio ◽

Real Data ◽

Information Criterion ◽

High Signal ◽

Data Sets ◽

Signal To Noise ◽

Arrival Times ◽

Common Time ◽

Waveform Similarity

We introduce two new traveltime picking schemes developed specifically for crosshole ground-penetrating radar (GPR) applications. The main objective is to automate, at least partially, the traveltime picking procedure and to provide first-arrival times that are closer in quality to those of manual picking approaches. The first scheme is an adaptation of a method based on cross-correlation of radar traces collated in gathers according to their associated transmitter-receiver angle. A detector is added to isolate the first cycle of the radar wave and to suppress secon-dary arrivals that might be mistaken for first arrivals. To improve the accuracy of the arrival times obtained from the crosscorrelation lags, a time-rescaling scheme is implemented to resize the radar wavelets to a common time-window length. The second method is based on the Akaike information criterion(AIC) and continuous wavelet transform (CWT). It is not tied to the restrictive criterion of waveform similarity that underlies crosscorrelation approaches, which is not guaranteed for traces sorted in common ray-angle gathers. It has the advantage of being automated fully. Performances of the new algorithms are tested with synthetic and real data. In all tests, the approach that adds first-cycle isolation to the original crosscorrelation scheme improves the results. In contrast, the time-rescaling approach brings limited benefits, except when strong dispersion is present in the data. In addition, the performance of crosscorrelation picking schemes degrades for data sets with disparate waveforms despite the high signal-to-noise ratio of the data. In general, the AIC-CWT approach is more versatile and performs well on all data sets. Only with data showing low signal-to-noise ratios is the AIC-CWT superseded by the modified crosscorrelation picker.

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Clocking the formation of today’s largest galaxies: wide field integral spectroscopy of brightest cluster galaxies and their surroundings

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2706 ◽

2019 ◽

Vol 491 (2) ◽

pp. 2617-2638 ◽

Cited By ~ 1

Author(s):

Louise O V Edwards ◽

Matthew Salinas ◽

Steffanie Stanley ◽

Priscilla E Holguin West ◽

Isabella Trierweiler ◽

...

Keyword(s):

Velocity Dispersion ◽

Minor Component ◽

High Signal ◽

Wide Field ◽

Cluster Galaxies ◽

Brightest Cluster Galaxies ◽

The Galaxy ◽

Formation And Evolution ◽

Intracluster Light ◽

A Minor

ABSTRACT The formation and evolution of local brightest cluster galaxies (BCGs) is investigated by determining the stellar populations and dynamics from the galaxy core, through the outskirts and into the intracluster light (ICL). Integral spectroscopy of 23 BCGs observed out to $4\, r_{e}$ is collected and high signal-to-noise regions are identified. Stellar population synthesis codes are used to determine the age, metallicity, velocity, and velocity dispersion of stars within each region. The ICL spectra are best modelled with populations that are younger and less metal-rich than those of the BCG cores. The average BCG core age of the sample is $\rm 13.3\pm 2.8\, Gyr$ and the average metallicity is $\rm [Fe/H] = 0.30\pm 0.09$, whereas for the ICL the average age is $\rm 9.2\pm 3.5\, Gyr$ and the average metallicity is $\rm [Fe/H] = 0.18\pm 0.16$. The velocity dispersion profile is seen to be rising or flat in most of the sample (17/23), and those with rising values reach the value of the host cluster’s velocity dispersion in several cases. The most extended BCGs are closest to the peak of the cluster’s X-ray luminosity. The results are consistent with the idea that the BCG cores and inner regions formed quickly and long ago, with the outer regions and ICL forming more recently, and continuing to assemble through minor merging. Any recent star formation in the BCGs is a minor component, and is associated with the cluster cool core status.

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A new technique for first-arrival picking of refracted seismic data based on digital image segmentation

Geophysics ◽

10.1190/geo2010-0322.1 ◽

2011 ◽

Vol 76 (5) ◽

pp. V79-V89 ◽

Cited By ~ 22

Author(s):

Wail A. Mousa ◽

Abdullatif A. Al-Shuhail ◽

Ayman Al-Lehyani

Keyword(s):

Image Segmentation ◽

Seismic Data ◽

Convex Sets ◽

Color Image ◽

Signal To Noise Ratio ◽

Real Data ◽

Color Image Segmentation ◽

High Signal ◽

Data Sets ◽

First Arrival

We introduce a new method for first-arrival picking based on digital color-image segmentation of energy ratios of refracted seismic data. The method uses a new color-image segmentation scheme based on projection onto convex sets (POCS). The POCS requires a reference color for the first break and one iteration to segment the first-break amplitudes from other arrivals. We tested the segmentation method on synthetic seismic data sets with various amounts of additive Gaussian noise. The proposed method gives similar performance to a modified version of Coppens’ method for traces with high signal-to-noise ratio and medium-to-large offsets. Finally, we applied our method and used as well the modified first-arrival picking method based on Coppens’ method to pick the first arrivals on four real data sets, where both were compared to the first breaks that were picked manually and then interpolated. Based on an assessment error of a 20-ms window with respect to manual picks that are interpolated, we find that our method gives comparable performance to Coppens’ method, depending on the data difficulty of picking first arrivals. Therefore, we believe that our proposed method is a good new addition to the existing methods of first-arrival picking.

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Comprehensive comparison between APOGEE and LAMOST

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833387 ◽

2018 ◽

Vol 620 ◽

pp. A76 ◽

Cited By ~ 10

Author(s):

B. Anguiano ◽

S. R. Majewski ◽

C. Allende-Prieto ◽

S. Meszaros ◽

H. Jönsson ◽

...

Keyword(s):

Galaxy Evolution ◽

Signal To Noise Ratio ◽

Chemical Species ◽

Stellar Atmosphere ◽

Radial Velocities ◽

High Signal ◽

Red Giants ◽

Stellar Parameter ◽

Comprehensive Comparison ◽

Red Giant

Context. In the era of massive spectroscopy surveys, automated stellar parameter pipelines and their validation are extremely important for an efficient scientific exploitation of the spectra. Aims. We undertake a critical and comprehensive comparison of the radial velocities and the main stellar atmosphere parameters for stars in common between the latest data releases from the Apache Point Observatory Galaxy Evolution Experiment (APOGEE) and the Large sky Area Multi-Object Spectroscopic Telescope (LAMOST) surveys. Methods. APOGEE is a high-resolution (R = 22 500) spectroscopic survey with high signal-to-noise ratio that is part of the Sloan Digital Sky Survey (SDSS). The latest data release, SDSS DR14, comprises APOGEE spectra for 263 444 stars, together with main stellar parameters and individual abundances for up to 20 chemical species. LAMOST is a low-resolution (R = 1800) optical spectroscopic survey also in the Northern Hemisphere, where 4000 fibers can be allocated simultaneously. LAMOST DR3 contains 3 177 995 stars. Results. A total of 42 420 dwarfs and giants stars are in common between the APOGEE DR14 – LAMOST DR3 stellar catalogs. A comparison between APOGEE and LAMOST RVs shows a clear offset of 4.54 ± 0.03 km s−1, with a dispersion of 5.8 km s−1, in the sense that APOGEE radial velocities are higher. We observe a small offset in the effective temperatures of about 13 K, with a scatter of 155 K. A small offset in [Fe/H] of about 0.06 dex together with a scatter of 0.13 dex is also observed. We note that the largest offset between the surveys occurs in the surface gravities. Using only surface gravities in calibrated red giants from APOGEE DR14, with which there are 24 074 stars in common, a deviation of 0.14 dex is found with substantial scatter (0.25 dex). There are 17 482 red giant stars in common between APOGEE DR14 and those in LAMOST tied to APOGEE DR12 via the code called the Cannon. There is generally good agreement between the two data-sets. However, we find that the differences in the stellar parameters depend on effective temperature. For metal-rich stars, a different trend for the [Fe/H] discrepancies is found. Surprisingly, we see no correlation between the internal APOGEE DR14 – DR12 differences in Teff and those in DR14 – LAMOST tied to DR12, where a correlation should be expected since LAMOST has been calibrated to APOGEE DR12. We find no correlation either between the [Fe/H] discrepancies, suggesting that LAMOST/Cannon is not well coupled to the APOGEE DR12 stellar parameter scale. An [Fe/H] dependence between the stellar parameters in APOGEE DR12 and those in DR14 is reported. We find a weak correlation in the differences between APOGEE DR14 – DR12 and LAMOST on DR12 surface gravity for stars hotter than 4800 K and in the log g range between 2.0 and 2.8 dex. We do not observe an [Fe/H] dependency in the gravity discrepancies.

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Unveiling the gravitational universe at μ-Hz frequencies

Experimental Astronomy ◽

10.1007/s10686-021-09709-9 ◽

2021 ◽

Author(s):

Alberto Sesana ◽

Natalia Korsakova ◽

Manuel Arca Sedda ◽

Vishal Baibhav ◽

Enrico Barausse ◽

...

Keyword(s):

Signal To Noise Ratio ◽

High Redshift ◽

Low Frequency ◽

High Signal ◽

Massive Black Hole ◽

Black Hole Binaries ◽

Pulsar Timing ◽

Laser Interferometer Space Antenna ◽

The Galaxy ◽

High Redshift Universe

AbstractWe propose a space-based interferometer surveying the gravitational wave (GW) sky in the milli-Hz to μ-Hz frequency range. By the 2040s, the μ-Hz frequency band, bracketed in between the Laser Interferometer Space Antenna (LISA) and pulsar timing arrays, will constitute the largest gap in the coverage of the astrophysically relevant GW spectrum. Yet many outstanding questions related to astrophysics and cosmology are best answered by GW observations in this band. We show that a μ-Hz GW detector will be a truly overarching observatory for the scientific community at large, greatly extending the potential of LISA. Conceived to detect massive black hole binaries from their early inspiral with high signal-to-noise ratio, and low-frequency stellar binaries in the Galaxy, this instrument will be a cornerstone for multimessenger astronomy from the solar neighbourhood to the high-redshift Universe.

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The VANDELS ESO public spectroscopic survey: Observations and first data release

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833047 ◽

2018 ◽

Vol 616 ◽

pp. A174 ◽

Cited By ~ 28

Author(s):

L. Pentericci ◽

R. J. McLure ◽

B. Garilli ◽

O. Cucciati ◽

P. Franzetti ◽

...

Keyword(s):

Galaxy Evolution ◽

Spectroscopic Data ◽

Signal To Noise Ratio ◽

High Redshift ◽

Measurement Procedure ◽

Integration Time ◽

High Signal ◽

Redshift Distribution ◽

Data Set ◽

Data Release

This paper describes the observations and the first data release (DR1) of the ESO public spectroscopic survey “VANDELS, a deep VIMOS survey of the CANDELS CDFS and UDS fields”. The main targets of VANDELS are star-forming galaxies at redshift 2.4 < z < 5.5, an epoch when the Universe had not yet reached 20% of its current age, and massive passive galaxies in the range 1 < z < 2.5. By adopting a strategy of ultra-long exposure times, ranging from a minimum of 20 h to a maximum of 80 h per source, VANDELS is specifically designed to be the deepest-ever spectroscopic survey of the high-redshift Universe. Exploiting the red sensitivity of the refurbished VIMOS spectrograph, the survey is obtaining ultra-deep optical spectroscopy covering the wavelength range 4800–10 000 Å with a sufficiently high signal-to-noise ratio to investigate the astrophysics of high-redshift galaxy evolution via detailed absorption line studies of well-defined samples of high-redshift galaxies. VANDELS-DR1 is the release of all medium-resolution spectroscopic data obtained during the first season of observations, on a 0.2 square degree area centered around the CANDELS-CDFS (Chandra deep-field south) and CANDELS-UDS (ultra-deep survey) areas. It includes data for all galaxies for which the total (or half of the total) scheduled integration time was completed. The DR1 contains 879 individual objects, approximately half in each of the two fields, that have a measured redshift, with the highest reliable redshifts reaching zspec ~ 6. In DR1 we include fully wavelength-calibrated and flux-calibrated 1D spectra, the associated error spectrum and sky spectrum, and the associated wavelength-calibrated 2D spectra. We also provide a catalog with the essential galaxy parameters, including spectroscopic redshifts and redshift quality flags measured by the collaboration. We present the survey layout and observations, the data reduction and redshift measurement procedure, and the general properties of the VANDELS-DR1 sample. In particular, we discuss the spectroscopic redshift distribution and the accuracy of the photometricredshifts for each individual target category, and we provide some examples of data products for the various target typesand the different quality flags. All VANDELS-DR1 data are publicly available and can be retrieved from the ESO archive. Two further data releases are foreseen in the next two years, and a final data release is currently scheduled for June 2020, which will include an improved rereduction of the entire spectroscopic data set.

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