scholarly journals SDSS-IV MaNGA: the spectroscopic discovery of strongly lensed galaxies

2018 ◽  
Vol 477 (1) ◽  
pp. 195-209 ◽  
Author(s):  
Michael S Talbot ◽  
Joel R Brownstein ◽  
Adam S Bolton ◽  
Kevin Bundy ◽  
Brett H Andrews ◽  
...  
Keyword(s):  
Emission Line ◽  
Narrow Band ◽  
Signal To Noise Ratio ◽  
Gravitational Lens ◽  
Emission Lines ◽  
High Signal ◽  
Common Source ◽  
Narrow Band Image ◽  
Background Emission ◽  
Field Unit

Abstract We present a catalogue of 38 spectroscopically detected strong galaxy–galaxy gravitational lens candidates identified in the Sloan Digital Sky Survey IV (SDSS-IV). We were able to simulate narrow-band images for eight of them demonstrating evidence of multiple images. Two of our systems are compound lens candidates, each with two background source-planes. One of these compound systems shows clear lensing features in the narrow-band image. Our sample is based on 2812 galaxies observed by the Mapping Nearby Galaxies at APO (MaNGA) integral field unit (IFU). This Spectroscopic Identification of Lensing Objects (SILO) survey extends the methodology of the Sloan Lens ACS Survey (SLACS) and BOSS Emission-Line Survey (BELLS) to lower redshift and multiple IFU spectra. We searched ∼1.5 million spectra, of which 3065 contained multiple high signal-to-noise ratio background emission-lines or a resolved [O ii] doublet, that are included in this catalogue. Upon manual inspection, we discovered regions with multiple spectra containing background emission-lines at the same redshift, providing evidence of a common source-plane geometry which was not possible in previous SLACS and BELLS discovery programs. We estimate more than half of our candidates have an Einstein radius ≳ 1.7 arcsec, which is significantly greater than seen in SLACS and BELLS. These larger Einstein radii produce more extended images of the background galaxy increasing the probability that a background emission-line will enter one of the IFU spectroscopic fibres, making detection more likely.

Dissecting quasars with the J-PAS narrow-band photometric survey

2019 ◽  
Vol 15 (S356) ◽  
pp. 12-16
Author(s):  
Silvia Bonoli ◽  
Giorgio Calderone ◽  
Raul Abramo ◽  
Jailson Alcaniz ◽  
Narciso Benitez ◽  
...  
Keyword(s):  
Emission Line ◽  
Wavelength Range ◽  
Software Package ◽  
Narrow Band ◽  
Active Galaxies ◽  
Emission Lines ◽  
Low Resolution ◽  
Strong Emission ◽  
Optical Wavelength ◽  
Quasar Spectra

AbstractThe J-PAS survey will soon start observing thousands of square degrees of the Northern Sky with its unique set of 56 narrow band filters covering the entire optical wavelength range, providing, effectively, a low resolution spectra for every object detected. Active galaxies and quasars, thanks to their strong emission lines, can be easily identified and characterized with J-PAS data. A variety of studies can be performed, from IFU-like analysis of local AGN, to clustering of high-z quasars. We also expect to be able to extract intrinsic physical quasar properties from the J-PAS pseudo-spectra, including continuum slope and emission line luminosities. Here we show the first attempts of using the QSFit software package to derive the properties for 22 quasars at 0.8 < z < 2 observed by the miniJPAS survey, the first deg2 of J-PAS data obtained with an interim camera. Results are compared with the ones obtained by applying the same software to SDSS quasar spectra.

scholarly journals Emission-Line Asymmetries and the Kinematics of the Narrow-Line Region in AGNs

1989 ◽  
Vol 134 ◽  
pp. 347-348
Author(s):  
Richard A. Shaw ◽  
Michael M. De Robertis
Keyword(s):  
Emission Line ◽  
Fundamental Problem ◽  
Signal To Noise Ratio ◽  
Critical Density ◽  
High Signal ◽  
Symmetric Model ◽  
Narrow Line ◽  
Line Region ◽  
Wide Range ◽  
Narrow Line Region

We have obtained high signal-to-noise ratio CCD spectra at ≤ 150 km/s resolution for 6 high-ionization Seyfert galaxies. We analyzed the profiles of the emission-lines over a wide range in both ionization potential (IP) and critical density (Ncr) in order to study the fundamental problem of cloud motion in the narrow-line region (NLR). Using the known correlations between FWHM and IP and/or Ncr for these galaxies, and assuming that the blueward profile asymmetries result from the combined effects of radially infalling or outflowing clouds and extinction within or between them, we deconvolve these effects by analyzing the correlation between emission-line asymmetries and both IP and Ncr. We find fair to good correlations in the sense that lines with high IP and Ncr also tend to have high asymmetry, while lines with low IP and Ncr have low but usually non-zero asymmetry. Simulated emission-line profiles generated with a spherically-symmetric model of a NLR suggest that the extinction arises primarily within radially infalling clouds.

scholarly journals The Timescales of Variations in Continuum and Hydrogen Lines During Stellar Flares

1983 ◽  
Vol 71 ◽  
pp. 239-243
Author(s):  
B.R. Pettersen
Keyword(s):  
Emission Line ◽  
Narrow Band ◽  
Light Curves ◽  
Emission Lines ◽  
Continuum Radiation ◽  
Stellar Flares ◽  
Hydrogen Lines ◽  
The Continuum

AbstractLight curves of major stellar flares have been used to study the behavior of U-B, B-V, and V-R. The majority of the flux transmitted through these filters is continuum radiation, but U and B are affected by emission lines. The variability of Ha and H$ emission lines were monitored through narrow band filters. The timescales of emission line variability are considerably longer than those for the continuum, and the emission line flare peak occurs a few minutes after the continuum flare maximum. No variability in lines at a timescale of seconds is detected in our data.

scholarly journals Quantitative classification of [WC] nuclei of Planetary Nebulae

1997 ◽  
Vol 180 ◽  
pp. 18-18 ◽  
Author(s):  
A. Acker ◽  
M. Parthasarathy ◽  
W. Leindecker ◽  
J. Koeppen ◽  
B. Stenholm
Keyword(s):  
Emission Line ◽  
Spectral Characteristics ◽  
Planetary Nebulae ◽  
Emission Lines ◽  
High Signal ◽  
Absorption Feature ◽  
Total Strength ◽  
Central Stars ◽  
Stellar Emission

We have carried out spectral classification of 65 [WC] stars, using spectra obtained at ESO in 1994-1995 with a spectral resolution of 1500 and high signal to noise ratio. We quantify the visual classification, by using the line ratios of CIII, CIV, OV, OVI in the 530-580 nm range, correlated with the blue CIII - IV lines. We measured the total strength of the above emission lines and derived the ratios of the emission line strengths. Using the stellar emission line ratios we classified about 32 CSPN as [WC] and about 30 as WELS which show only relatively weak CIV 5806 and CIV 4650 and He II 4686 stellar emission lines. The presence of CIV 5806 and the absence of CIII 5696 the WELS appear to belong to the [WC3] type. However the OV lines are very weak or absent. Some stars are reclassified, and 4 stars are found in the [WC5-7] gap. We classified 34 CSPN as [WC]. The [WC2] CSPN NGC 2867 and PB 6 show narrow and weak He II 5412 absorption feature. Based on the relative strengths of the stellar emission features NGC 2867 [WC 2], PB 6 [WC2] and M1-61 [WC4] appear to be related to WELS (Weak Emission Line Central Stars of Planetary Nebulae). The observed spectral characteristics of the central stars of these PN suggest that they are related to [WC] - PG 1159 type of objects.

scholarly journals Dichotomy of radio loud and radio quiet quasars in four dimensional eigenvector one (4DE1) parameter space

2019 ◽  
Vol 15 (S356) ◽  
pp. 351-354
Author(s):  
Shimeles Terefe ◽  
Ascensión del Olmo ◽  
Paola Marziani ◽  
Mirjana Pović
Keyword(s):  
Emission Line ◽  
Parameter Space ◽  
Signal To Noise Ratio ◽  
High Redshift ◽  
Emission Lines ◽  
Signal To Noise ◽  
Broad Emission ◽  
Broad Emission Line ◽  
Two Populations ◽  
Calar Alto

AbstractRecent work has shown that it is possible to systematize quasars (QSOs) spectral diversity in 4DE1 parameter space. The spectra contained in most of the surveys have low signal to noise ratio which fed the impression that all QSO’s are spectroscopically similar. Exploration of 4DE1 parameter space gave rise to the concept of two populations of QSOs that present important spectroscopic differences. We aim to quantify broad emission line differences between radio quiet and radio loud sources by exploiting more complete samples of QSO with spectral coverage in Hβ, MgII and CIV emission lines. We used a high redshift sample (0.35 < z < 1) of strong radio emitter QSOs observations from Calar Alto Observatory in Spain.

scholarly journals The GALAH survey: characterization of emission-line stars with spectral modelling using autoencoders

2020 ◽  
Vol 500 (4) ◽  
pp. 4849-4865
Author(s):  
Klemen Čotar ◽  
Tomaž Zwitter ◽  
Gregor Traven ◽  
Joss Bland-Hawthorn ◽  
Sven Buder ◽  
...  
Keyword(s):  
Emission Line ◽  
Rarefied Gas ◽  
Signal To Noise Ratio ◽  
Emission Spectra ◽  
High Signal ◽  
Physical Mechanisms ◽  
Repeated Observation ◽  
Hα Emission ◽  
The Continuum

ABSTRACT We present a neural network autoencoder structure that is able to extract essential latent spectral features from observed spectra and then reconstruct a spectrum from those features. Because of the training with a set of unpeculiar spectra, the network is able to reproduce a spectrum of high signal-to-noise ratio that does not show any spectral peculiarities, even if they are present in an observed spectrum. Spectra generated in this manner were used to identify various emission features among spectra acquired by multiple surveys using the HERMES spectrograph at the Anglo-Australian telescope. Emission features were identified by a direct comparison of the observed and generated spectra. Using the described comparison procedure, we discovered 10 364 candidate spectra with varying intensities (from partially filled-in to well above the continuum) of the Hα/Hβ emission component, produced by different physical mechanisms. A fraction of these spectra belong to the repeated observation that shows temporal variability in their emission profile. Among the emission spectra, we find objects that feature contributions from a nearby rarefied gas (identified through the emission of [N ii] and [S ii] lines) that was identified in 4004 spectra, which were not all identified as having Hα emission. The positions of identified emission-line objects coincide with multiple known regions that harbour young stars. Similarly, detected nebular emission spectra coincide with visually prominent nebular clouds observable in the red all-sky photographic composites.

scholarly journals The effect of emission lines on the performance of photometric redshift estimation algorithms

2021 ◽  
Author(s):  
Géza Csörnyei ◽  
László Dobos ◽  
István Csabai
Keyword(s):  
Emission Line ◽  
Signal To Noise Ratio ◽  
Emission Lines ◽  
Estimation Methods ◽  
Physical Parameters ◽  
Model Parameters ◽  
Colour Space ◽  
Strong Emission ◽  
Photometric Redshift ◽  
Photometric Error

Abstract We investigate the effect of strong emission line galaxies on the performance of empirical photometric redshift estimation methods. In order to artificially control the contribution of photometric error and emission lines to total flux, we develop a PCA-based stochastic mock catalogue generation technique that allows for generating infinite signal-to-noise ratio model spectra with realistic emission lines on top of theoretical stellar continua. Instead of running the computationally expensive stellar population synthesis and nebular emission codes, our algorithm generates realistic spectra with a statistical approach, and – as an alternative to attempting to constrain the priors on input model parameters – works by matching output observational parameters. Hence, it can be used to match the luminosity, colour, emission line and photometric error distribution of any photometric sample with sufficient flux-calibrated spectroscopic follow-up. We test three simple empirical photometric estimation methods and compare the results with and without photometric noise and strong emission lines. While photometric noise clearly dominates the uncertainty of photometric redshift estimates, the key findings are that emission lines play a significant role in resolving colour space degeneracies and good spectroscopic coverage of the entire colour space is necessary to achieve good results with empirical photo-z methods. Template fitting methods, on the other hand, must use a template set with sufficient variation in emission line strengths and ratios, or even better, first estimate the redshift empirically and fit the colours with templates at the best-fit redshift to calculate the K-correction and various physical parameters.

scholarly journals [C II] 158 μm self-absorption and optical depth effects

2020 ◽  
Vol 636 ◽  
pp. A16 ◽  
Author(s):  
C. Guevara ◽  
J. Stutzki ◽  
V. Ossenkopf-Okada ◽  
R. Simon ◽  
J. P. Pérez-Beaupuits ◽  
...  
Keyword(s):  
Optical Depth ◽  
Column Density ◽  
Signal To Noise Ratio ◽  
Far Infrared ◽  
Emission Lines ◽  
High Spectral Resolution ◽  
Line Of Sight ◽  
High Signal ◽  
Line Profiles ◽  
Star Forming

Context. The [C II] 158 μm far-infrared fine-structure line is one of the most important cooling lines of the star-forming interstellar medium (ISM). It is used as a tracer of star formation efficiency in external galaxies and to study feedback effects in parental clouds. High spectral resolution observations have shown complex structures in the line profiles of the [C II] emission. Aims. Our aim is to determine whether the complex profiles observed in [12C II] are due to individual velocity components along the line-of-sight or to self-absorption based on a comparison of the [12C II] and isotopic [13C II] line profiles. Methods. Deep integrations with the SOFIA/upGREAT 7-pixel array receiver in the sources of M43, Horsehead PDR, Monoceros R2, and M17 SW allow for the detection of optically thin [13C II] emission lines, along with the [12C II] emission lines, with a high signal-to-noise ratio. We first derived the [12C II] optical depth and the [C II] column density from a single component model. However, the complex line profiles observed require a double layer model with an emitting background and an absorbing foreground. A multi-component velocity fit allows us to derive the physical conditions of the [C II] gas: column density and excitation temperature. Results. We find moderate to high [12C II] optical depths in all four sources and self-absorption of [12C II] in Mon R2 and M17 SW. The high column density of the warm background emission corresponds to an equivalent Av of up to 41 mag. The foreground absorption requires substantial column densities of cold and dense [C II] gas, with an equivalent Av ranging up to about 13 mag. Conclusions. The column density of the warm background material requires multiple photon-dominated region surfaces stacked along the line of sight and in velocity. The substantial column density of dense and cold foreground [C II] gas detected in absorption cannot be explained with any known scenario and we can only speculate on its origins.

scholarly journals A 2μm narrow-band survey for emission-line stars in the inner Galaxy

1999 ◽  
Vol 193 ◽  
pp. 472-473
Author(s):  
Robert D. Blum ◽  
Augusto Damineli
Keyword(s):  
Emission Line ◽  
Near Infrared ◽  
Narrow Band ◽  
Emission Lines ◽  
Evolved Stars ◽  
The Galaxy ◽  
Band Survey

We have begun a search for emission-line stars toward the inner Galaxy using narrow-band photometry centered on the emission lines of He I 2.06μm, C IV 2.08μm, H I Brγ 2.166μm and He II 2.189μm. The census of Wolf-Rayet and other emission-line stars in the Galaxy is incomplete, owing to the large extinction at optical and shorter wavelengths toward the inner Galaxy. However, these massive, evolved stars are bright and can be detected at large distances in the near infrared.

scholarly journals Helium Abundance in the Most Metal-Deficient Dwarf Galaxies

1999 ◽  
Vol 171 ◽  
pp. 390-392
Author(s):  
Y.I. Izotov
Keyword(s):  
Mass Fraction ◽  
Dwarf Galaxies ◽  
Signal To Noise Ratio ◽  
Emission Lines ◽  
High Signal ◽  
Weighted Mean ◽  
Ratio Spectrum ◽  
Abundance Determination ◽  
Better Than ◽  
The Continuum

AbstractThe high-quality long-exposure spectroscopic observations of the two most-metal deficient blue compact galaxies I Zw 18 and SBS 0335–052 are discussed. We confirm previous findings that underlying stellar absorption strongly influences the observed intensities of He I emission lines in the brightest NW component of I Zw 18, and hence this component should not be used for primordial He abundance determination. The effect of underlying stellar absorption, though present, is much smaller in the SE component. The extremely high signal-to-noise ratio spectrum (≥ 100 in the continuum) of the BCG SBS 0335–052 allows us to measure the helium mass fraction with precision better than 2% in nine different regions along the slit. The weighted mean of helium mass fraction in two most metal-deficient BCGs I Zw 18 and SBS 0335–052, Y=0.2462±0.0009, after correction for the He production in massive stars results in primordial He mass fraction Yp = 0.2452±0.0009.

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