Statistical methods for astronomical data with upper limits. II - Correlation and regression

Isobe, Takashi; Feigelson, E. D.; Nelson, Paul I.

doi:10.1086/164359

Cited by 672 publications

(697 citation statements)

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“…12 shows that the two Lx/M⋆ distributions appear very different, with RQ AGN having much larger values. Given the substantial fraction of upper limits (all on Lx) we used ASURV (Lavalley, Isobe, & Feigelson 1992), the Survival Analysis package which employs the routines described in Feigelson & Nelson (1985) and Isobe et al (1986), which evaluate mean values by dealing properly with non-detections and also compute the probability that two samples are drawn from the same parent population. RQ and RL AGN have totally different (pvalues < 0.001) distributions, according to all two-sample tests in ASURV.…”

Section: Astrophysics Of Micro-jy Sourcesmentioning

confidence: 99%

Radio-faint AGN: a tale of two populations

Padovani

Bonzini

Kellermann

et al. 2015

Mon. Not. R. Astron. Soc.

130

167

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We study the Extended Chandra Deep Field South (E-CDFS) Very Large Array sample, which reaches a flux density limit at 1.4 GHz of 32.5 µJy at the field centre and redshift ∼ 4, and covers ∼ 0.3 deg 2 . Number counts are presented for the whole sample while the evolutionary properties and luminosity functions are derived for active galactic nuclei (AGN). The faint radio sky contains two totally distinct AGN populations, characterised by very different evolutions, luminosity functions, and Eddington ratios: radio-quiet (RQ)/radiative-mode, and radioloud/jet-mode AGN. The radio power of RQ AGN evolves ∼ ∝ (1 + z) 2.5 , similarly to star-forming galaxies, while the number density of radio-loud ones has a peak at z ∼ 0.5 and then declines at higher redshifts. The number density of radioselected RQ AGN is consistent with that of X-ray selected AGN, which shows that we are sampling the same population. The unbiased fraction of radiativemode RL AGN, derived from our own and previously published data, is a strong function of radio power, decreasing from ∼ 0.5 at P 1.4GHz ∼ 10 24 W Hz −1 to ∼ 0.04 at P 1.4GHz ∼ 10 22 W Hz −1 . Thanks to our enlarged sample, which now includes ∼ 700 radio sources, we also confirm and strengthen our previous results on the source population of the faint radio sky: star-forming galaxies start to dominate the radio sky only below ∼ 0.1 mJy, which is also where radio-quiet AGN overtake radio-loud ones.

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Section: Astrophysics Of Micro-jy Sourcesmentioning

confidence: 99%

Radio-faint AGN: a tale of two populations

Padovani

Bonzini

Kellermann

et al. 2015

Mon. Not. R. Astron. Soc.

130

167

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“…As per usual (e.g. Curran et al 2016c), we include the H I 21-cm non-detected 3σ limits as censored points via the Astronomy SURVival Analysis (ASURV) package (Isobe et al 1986). A generalised non-parametric Kendall-tau test gives a probability of P (τ ) = 2.53 × 10 −4 of the correlation occuring by chance, which is significant at S(τ ) = 3.66σ, assuming Gaussian statistics.…”

Section: Dust Reddeningmentioning

confidence: 99%

“…GALEX is operated for NASA by the California Institute of Technology under NASA contract NAS5-98034. This research has also made use of NASA's Astrophysics Data System Bibliographic Services and ASURV Rev 1.2 (Lavalley et al 1992), which implements the methods presented in Isobe et al (1986).…”

Section: Acknowledgementsmentioning

confidence: 99%

Atomic and molecular absorption in redshifted radio sources

Curran

Whiting

Allison

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We report on a survey for associated H I 21-cm and OH 18-cm absorption with the Giant Metrewave Radio Telescope at redshifts z ≈ 0.2 − 0.4. Although the low redshift selection ensures that our targets are below the critical ultra-violet luminosity (L UV ∼ 10 23 W Hz −1 ), which is hypothesised to ionise all of the neutral gas in the host galaxy, we do not obtain any detections in the six sources searched. Analysing these in context of the previous surveys, in addition to the anti-correlation with the ultra-violet luminosity (ionising photon rate), we find a correlation between the strength of the absorption and the blue -near-infrared colour, as well as the radio-band turnover frequency. We believe that these are due to the photo-ionisation of the neutral gas, an obscured sight-line being more conducive to the presence of cold gas and the compact radio emission being better intercepted by the absorbing gas, maximising the flux coverage, respectively. Regarding the photo-ionisation, the compilation of the previous surveys increases the significance of the critical ionising photon rate, above which all of the gas in the host galaxy is hypothesised to be ionised (Q H I ≈ 3 × 10 56 sec −1 ), to > 5σ. This reaffirms that this is an ubiquitous effect, which has profound implications for the detection of neutral gas in these objects with the Square Kilometre Array.

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“…a and b are the fitting parameters of log(Y )=a·log(X)+b. Note that we used the Bucley-James least squares linear regression method implemented in the ASURV survival analysis package (Feigelson & Nelson 1985;Isobe, Feigelson, & Nelson 1986). ⋆ and † correspond to the BCS 40 sample, but excluding NGC 4395 and the AGN-dominated sources, respectively.…”

Section: Mir Correlations With Agn and Sf Indicatorsmentioning

confidence: 99%

The nuclear and extended mid-infrared emission of Seyfert galaxies

García-Bernete¹,

Almeida²,

Acosta–Pulido³

et al. 2016

Mon. Not. R. Astron. Soc.

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We present subarcsecond resolution mid-infrared (MIR) images obtained with 8-10 m-class ground-based telescopes of a complete volume-limited (D L <40 Mpc) sample of 24 Seyfert galaxies selected from the Swift/BAT nine month catalog. We use those MIR images to study the nuclear and circumnuclear emission of the galaxies. Using different methods to classify the MIR morphologies on scales of ∼400 pc, we find that the majority of the galaxies (75-83%) are extended or possibly extended and 17-25% are point-like. This extended emission is compact and it has low surface brightness compared with the nuclear emission, and it represents, on average, ∼30% of the total MIR emission of the galaxies in the sample. We find that the galaxies whose circumnuclear MIR emission is dominated by star formation show more extended emission (650±700 pc) than AGN-dominated systems (300±100 pc). In general, the galaxies with point-like MIR morphologies are face-on or moderately inclined (b/a∼0.4-1.0), and we do not find significant differences between the morphologies of Sy1 and Sy2. We used the nuclear and circumnuclear fluxes to investigate their correlation with different AGN and SF activity indicators. We find that the nuclear MIR emission (the inner ∼70 pc) is strongly correlated with the X-ray emission (the harder the X-rays the better the correlation) and with the [O IV] λ25.89 µm emission line, indicating that it is AGN-dominated. We find the same results, although with more scatter, for the circumnuclear emission, which indicates that the AGN dominates the MIR emission in the inner ∼400 pc of the galaxies, with some contribution from star formation.

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Statistical methods for astronomical data with upper limits. II - Correlation and regression

Cited by 672 publications

References 0 publications

Radio-faint AGN: a tale of two populations

Radio-faint AGN: a tale of two populations

Atomic and molecular absorption in redshifted radio sources

The nuclear and extended mid-infrared emission of Seyfert galaxies

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