scholarly journals THE HIGH A V Quasar Survey: Reddened Quasi-Stellar Objects selected from optical/near-infrared photometry. II.

2015 ◽  
Vol 217 (1) ◽  
pp. 5 ◽  
Author(s):  
J.-K. Krogager ◽  
S. Geier ◽  
J. P. U. Fynbo ◽  
B. P. Venemans ◽  
C. Ledoux ◽  
...  
Keyword(s):  
Near Infrared ◽  
Infrared Photometry ◽  
Stellar Objects ◽  
Quasi Stellar Objects

scholarly journals Quasi-stellar object redshift estimates from optical, near-infrared, and ultraviolet colours

2019 ◽  
Vol 629 ◽  
pp. A56 ◽  
Author(s):  
S. J. Curran ◽  
J. P. Moss
Keyword(s):  
Active Galactic Nuclei ◽  
Rest Frame ◽  
Near Infrared ◽  
Galactic Nuclei ◽  
Additional Contribution ◽  
Stellar Objects ◽  
Simple Estimate ◽  
Photometric Redshift ◽  
Wide Range ◽  
Quasi Stellar Objects

A simple estimate of the photometric redshift would prove invaluable to forthcoming continuum surveys on the next generation of large radio telescopes, as well as mitigating the existing bias towards the most optically bright sources. While there is a well-known correlation between the near-infrared K-band magnitude and redshift for galaxies, we find the K − z relation to break down for samples dominated by quasi-stellar objects. We hypothesise that this is due to the additional contribution to the near-infrared flux by the active galactic nucleus, and, as such, the K-band magnitude can only provide a lower limit to the redshift in the case of active galactic nuclei, which will dominate the radio surveys. From a large optical dataset, we find a tight relationship between the rest-frame (U − K)/(W2 − FUV) colour ratio and spectroscopic redshift over a sample of 17 000 sources, spanning z ≈ 0.1−5. Using the observed-frame ratios of (U − K)/(W2 − FUV) for redshifts of z ≲ 1, (I − W2)/(W3 − U) for 1 ≲ z ≲ 3, and (I − W2.5)/(W4 − R) for z ≳ 3, where W2.5 is the λ = 8.0 μm magnitude and the appropriate redshift ranges are estimated from the W2 (4.5 μm) magnitude, we find this to be a robust photometric redshift estimator for quasars. We suggest that the rest-frame U − K colour traces the excess flux from the AGN over this wide range of redshifts, although the W2 − FUV colour is required to break the degeneracy.

scholarly journals Detecting the highest redshift (z > 8) quasi-stellar objects in a wide, near-infrared slitless spectroscopic survey

2012 ◽  
Vol 420 (2) ◽  
pp. 1764-1778 ◽  
Author(s):  
Nathan Roche ◽  
Paolo Franzetti ◽  
Bianca Garilli ◽  
Giovanni Zamorani ◽  
Andrea Cimatti ◽  
...  
Keyword(s):  
Near Infrared ◽  
Stellar Objects ◽  
Quasi Stellar Objects

scholarly journals QSO photometric redshifts from SDSS, WISE, and GALEX colours

2020 ◽  
Vol 493 (1) ◽  
pp. L70-L75
Author(s):  
S J Curran
Keyword(s):  
Near Infrared ◽  
Empirical Method ◽  
Machine Learning Techniques ◽  
Radio Sources ◽  
Photometric Redshifts ◽  
Stellar Objects ◽  
Vast Number ◽  
Quasi Stellar Objects ◽  
Continuum Radio ◽  
Non Gaussian

ABSTRACT Machine learning techniques, specifically the k-nearest neighbour algorithm applied to optical band colours, have had some success in predicting photometric redshifts of quasi-stellar objects (QSOs): Although the mean of differences between the spectroscopic and photometric redshifts, Δ$z$, is close to zero, the distribution of these differences remains wide and distinctly non-Gaussian. As per our previous empirical estimate of photometric redshifts, we find that the predictions can be significantly improved by adding colours from other wavebands, namely the near-infrared and ultraviolet. Self-testing this, by using half of the 33 643 strong QSO sample to train the algorithm, results in a significantly narrower spread in Δ$z$ for the remaining half of the sample. Using the whole QSO sample to train the algorithm, the same set of magnitudes return a similar spread in Δ$z$ for a sample of radio sources (quasars). Although the matching coincidence is relatively low (739 of the 3663 sources having photometry in the relevant bands), this is still significantly larger than from the empirical method (2 per cent) and thus may provide a method with which to obtain redshifts for the vast number of continuum radio sources expected to be detected with the next generation of large radio telescopes.

scholarly journals Developing a photometric estimate of quasar redshifts: An independent measurement of the distances to the most powerful objects in the Universe

2021 ◽  
Author(s):  
◽  
Jeremy Moss
Keyword(s):  
Near Infrared ◽  
Line Emission ◽  
Sloan Digital Sky Survey ◽  
Robust Estimator ◽  
Simple Method ◽  
Stellar Objects ◽  
Photometric Redshift ◽  
Quasi Stellar Objects ◽  
Computationally Intensive ◽  
Luminous Objects

<p>While spectroscopy is the standard method of measuring the redshift of luminous objects, it is a time-intensive technique, requiring, in some cases, hours of telescope time for a single source. Additionally, spectroscopy favours brighter objects, and therefore introduces an intrinsic bias towards luminous or closer sources. A simple method of estimating the redshift through photometry would prove invaluable to forthcoming surveys on the next generation of large radio telescopes, as well as alleviating the inherent bias towards the most optically bright sources. While there is a well-established correlation between the near-infrared K-band magnitude and redshift for galaxies, we find that the K-z relation breaks down for samples dominated by quasi-stellar objects (QSOs).  Current methods of estimating photometric redshift rely either on template spectra, which requires a high number of infrared photometry points, or computationally intensive machine learning methods.  Using photometric data from the Sloan Digital Sky Survey (SDSS) we investigate the relationship between combinations of magnitudes of a group of quasars, and their redshift. We find a high correlation between the colour relation (I-W2)/(W3-U) and redshift for a group of broad-line emission sources from the SDSS, and we conclude that this could be a robust estimator of the redshift.</p>

scholarly journals Modeling the Unresolved NIR–MIR SEDs of Local (z < 0.1) QSOs

2021 ◽  
Vol 922 (2) ◽  
pp. 157
Author(s):  
M. Martínez-Paredes ◽  
O. González-Martín ◽  
K. HyeongHan ◽  
S. Geier ◽  
I. García-Bernete ◽  
...  
Keyword(s):  
Accretion Disk ◽  
Near Infrared ◽  
Angular Resolution ◽  
High Angular Resolution ◽  
Two Phase ◽  
Stellar Objects ◽  
Mid Infrared ◽  
Disk Wind ◽  
Quasi Stellar Objects ◽  
Nir Emission

Abstract To study the nuclear (≲1 kpc) dust of nearby (z < 0.1) quasi-stellar objects (QSOs), we obtained new near-infrared (NIR) high angular resolution (∼0.″3) photometry in the H and Ks bands for 13 QSOs with available mid-infrared (MIR) high angular resolution spectroscopy (∼7.5–13.5 μm). We find that in most QSOs, the NIR emission is unresolved. We subtract the contribution from the accretion disk, which decreases from NIR (∼35%) to MIR (∼2.4%). We also estimate these percentages assuming a bluer accretion disk and find that the contribution in the MIR is nearly seven times larger. We find that the majority of objects (64%, 9/13) are better fitted by the disk+wind H17 model, while others can be fitted by the smooth F06 (14%, 2/13), clumpy N08 (7%, 1/13), clumpy H10 (7%, 1/13), and two-phase media S16 (7%, 1/13) models. However, if we assume the bluer accretion disk, the models fit only 2/13 objects. We measured two NIR-to-MIR spectral indexes, α NIR−MIR(1.6–8.7 μm) and α NIR−MIR(2.2–8.7 μm), and two MIR spectral indexes, α MIR(7.8–9.8 μm) and α MIR(9.8–11.7 μm), from models and observations. From observations, we find that the NIR-to-MIR spectral indexes are ∼−1.1, and the MIR spectral indexes are ∼−0.3. Comparing the synthetic and observed values, we find that none of the models simultaneously match the measured NIR-to-MIR and 7.8–9.8 μm slopes. However, we note that measuring α MIR(7.8–9.8 μm) on the starburst-subtracted Spitzer/IRS spectrum gives values of the slopes (∼−2) that are similar to the synthetic values obtained from the models.

scholarly journals The Optical Polarization of Near‐Infrared–selected Quasi‐Stellar Objects

2002 ◽  
Vol 569 (1) ◽  
pp. 23-35 ◽  
Author(s):  
Paul S. Smith ◽  
Gary D. Schmidt ◽  
Dean C. Hines ◽  
Roc M. Cutri ◽  
Brant O. Nelson
Keyword(s):  
Near Infrared ◽  
Optical Polarization ◽  
Stellar Objects ◽  
Quasi Stellar Objects

scholarly journals OPTICAL/NEAR-INFRARED SELECTION OF RED QUASI-STELLAR OBJECTS: EVIDENCE FOR STEEP EXTINCTION CURVES TOWARD GALACTIC CENTERS?

2012 ◽  
Vol 204 (1) ◽  
pp. 6 ◽  
Author(s):  
J. P. U. Fynbo ◽  
J.-K. Krogager ◽  
B. Venemans ◽  
P. Noterdaeme ◽  
M. Vestergaard ◽  
...  
Keyword(s):  
Near Infrared ◽  
Stellar Objects ◽  
Galactic Centers ◽  
Quasi Stellar Objects ◽  
Selection Of

scholarly journals The intrinsic reddening of the Magellanic Clouds as traced by background galaxies – I. The bar and outskirts of the Small Magellanic Cloud

2019 ◽  
Vol 489 (3) ◽  
pp. 3200-3217
Author(s):  
Cameron P M Bell ◽  
Maria-Rosa L Cioni ◽  
A H Wright ◽  
Stefano Rubele ◽  
David L Nidever ◽  
...  
Keyword(s):  
Near Infrared ◽  
Broad Band ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
Spectral Energy ◽  
Small Magellanic Cloud ◽  
Energy Distributions ◽  
Stellar Objects ◽  
Quasi Stellar Objects ◽  
Low Levels

ABSTRACT We present a method to map the total intrinsic reddening of a foreground extinguishing medium via the analysis of spectral energy distributions (SEDs) of background galaxies. In this pilot study, we implement this technique in two distinct regions of the Small Magellanic Cloud (SMC) – the bar and the southern outskirts – using a combination of optical and near-infrared ugrizYJKs broad-band imaging. We adopt the lephare χ2-minimization SED-fitting routine and various samples of galaxies and/or quasi-stellar objects to investigate the intrinsic reddening. We find that only when we construct reddening maps using objects classified as galaxies with low levels of intrinsic reddening (i.e. ellipticals/lenticulars and early-type spirals), the resultant maps are consistent with previous literature determinations, i.e. the intrinsic reddening of the SMC bar is higher than that in the outer environs. We employ two sets of galaxy templates – one theoretical and one empirical – to test for template dependences in the resulting reddening maps and find that the theoretical templates imply systematically higher reddening values by up to 0.20 mag in E(B − V). A comparison with previous reddening maps, based on the stellar components of the SMC, typically shows reasonable agreement. There is, however, significant variation amongst the literature reddening maps as to the level of intrinsic reddening associated with the bar. Thus, it is difficult to unambiguously state that instances of significant discrepancies are the result of appreciable levels of dust not accounted for in some literature reddening maps or whether they reflect issues with our adopted methodology.

scholarly journals Developing a photometric estimate of quasar redshifts: An independent measurement of the distances to the most powerful objects in the Universe

2021 ◽  
Author(s):  
◽  
Jeremy Moss
Keyword(s):  
Near Infrared ◽  
Line Emission ◽  
Sloan Digital Sky Survey ◽  
Robust Estimator ◽  
Simple Method ◽  
Stellar Objects ◽  
Photometric Redshift ◽  
Quasi Stellar Objects ◽  
Computationally Intensive ◽  
Luminous Objects

<p>While spectroscopy is the standard method of measuring the redshift of luminous objects, it is a time-intensive technique, requiring, in some cases, hours of telescope time for a single source. Additionally, spectroscopy favours brighter objects, and therefore introduces an intrinsic bias towards luminous or closer sources. A simple method of estimating the redshift through photometry would prove invaluable to forthcoming surveys on the next generation of large radio telescopes, as well as alleviating the inherent bias towards the most optically bright sources. While there is a well-established correlation between the near-infrared K-band magnitude and redshift for galaxies, we find that the K-z relation breaks down for samples dominated by quasi-stellar objects (QSOs).  Current methods of estimating photometric redshift rely either on template spectra, which requires a high number of infrared photometry points, or computationally intensive machine learning methods.  Using photometric data from the Sloan Digital Sky Survey (SDSS) we investigate the relationship between combinations of magnitudes of a group of quasars, and their redshift. We find a high correlation between the colour relation (I-W2)/(W3-U) and redshift for a group of broad-line emission sources from the SDSS, and we conclude that this could be a robust estimator of the redshift.</p>

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