Abstracts of general addresses [Dr. Michael E. Sadler]

Sadler, Michael

doi:10.1037/e533602009-219

Cited by 8 publications

(10 citation statements)

References 0 publications

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“…The summed radio luminosity function of all radio sources, together with its separation into starforming galaxies and radio-loud AGN, is provided in Table 2 and shown in Fig. 3, and these are in excellent agreement with previous determinations (Machalski & Godlowski 2000;Sadler et al 2002;Best et al 2005a;Mauch & Sadler 2007). Uncertainties quoted are the statistical Poissonian errors only; at some luminosities these are so small that they will be underestimates, with systematic errors dominating.…”

Section: Local Radio Luminosity Functions Of Hergs and Lergssupporting

confidence: 86%

“…3 shows the radio luminosity functions derived for starforming galaxies and radio-loud AGN. The smooth nature of the derived luminosity functions, especially at low and high luminosities where small numbers of misclassifications would have pronounced effects, offers broad support to the success of the classification scheme, as does the comparison with previous determinations from Machalski & Godlowski (2000), Sadler et al (2002) and Mauch & Sadler (2007). The slight offset of the AGN line from previous determinations below a radio luminosity of L ≈ 10 23 W Hz −1 may be caused by the different classification of radio-quiet AGN, which here are classified along with the star-forming galaxies.…”

Section: A2 Combination Into a Final Classificationsupporting

confidence: 56%

“…Filled points connected by solid lines indicate the data derived in this paper. For comparison, the results of Machalski & Godlowski (2000) using the Las Campanas Redshift Survey, Sadler et al (2002) using the 2‐degree field Galaxy Redshift Survey and Mauch & Sadler (2007) using the 6‐degree field Galaxy Survey are shown.…”

Section: Fundamental Properties Of the Radio Sourcesmentioning

confidence: 99%

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On the fundamental dichotomy in the local radio-AGN population: accretion, evolution and host galaxy properties

Best

Heckman

2012

Monthly Notices of the Royal Astronomical Society

690

123

1,193

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A sample of 18 286 radio‐loud active galactic nuclei (AGN) is presented, constructed by combining the seventh data release of the Sloan Digital Sky Survey with the NRAO (National Radio Astronomy Observatory) VLA (Very Large Array) Sky Survey (NVSS) and the Faint Images of the Radio Sky at Twenty centimetres (FIRST) survey. Using this sample, the differences between radio galaxies of ‘high‐excitation’ (‘quasar‐mode’; hereafer HERG) and ‘low‐excitation’ (‘radio‐mode’; LERG) are investigated. A primary difference between the two radio source classes is the distinct nature of the Eddington‐scaled accretion rate on to their central black holes: HERGs typically have accretion rates between one per cent and 10 per cent of their Eddington rate, whereas LERGs predominately accrete at a rate below one per cent Eddington. This is consistent with models whereby the population dichotomy is caused by a switch between radiatively efficient and radiatively inefficient accretion modes at low accretion rates. Local radio luminosity functions are derived separately for the two populations, for the first time, showing that although LERGs dominate at low radio luminosity and HERGs begin to take over at L1.4 GHz∼ 1026 W Hz−1, examples of both classes are found at all radio luminosities. Using the V/Vmax test it is shown that the two populations show differential cosmic evolution at fixed radio luminosity: HERGs evolve strongly at all radio luminosities, while LERGs show weak or no evolution. This suggests that the luminosity dependence of the evolution previously seen in the radio luminosity function is driven, at least in part, by the changing relative contributions of these two populations with luminosity. The host galaxies of the radio sources are also distinct: HERGs are typically of lower stellar mass, with lower black hole masses, bluer colours, lower concentration indices and less pronounced 4000 Å breaks indicating younger stellar populations. Even if samples are matched in radio luminosity and stellar and black hole masses, significant differences still remain between the accretion rates, stellar populations and structural properties of the host galaxies of the two radio source classes. These results offer strong support to the developing picture of radio‐loud AGN in which HERGs are fuelled at high rates through radiatively efficient standard accretion discs by cold gas, perhaps brought in through mergers and interactions, while LERGs are fuelled via radiatively inefficient flows at low accretion rates. In this picture, the gas supplying the LERGs is frequently associated with the hot X‐ray haloes surrounding massive galaxies, groups and clusters, as part of a radio‐AGN feedback loop.

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Section: Local Radio Luminosity Functions Of Hergs and Lergssupporting

confidence: 86%

Section: A2 Combination Into a Final Classificationsupporting

confidence: 56%

Section: Fundamental Properties Of the Radio Sourcesmentioning

confidence: 99%

See 1 more Smart Citation

On the fundamental dichotomy in the local radio-AGN population: accretion, evolution and host galaxy properties

Best

Heckman

2012

Monthly Notices of the Royal Astronomical Society

690

123

1,193

View full text Add to dashboard Cite

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“…This suggests that hotter, perhaps more AGN‐rich galaxies, are represented in this more luminous, partially radio‐selected sample. A similar sample of approximately 40 luminous southern galaxies, with radio images from the Molonglo telescope and redshifts from the 2dF multi‐object spectrograph has recently been compiled by Sadler et al (2002), and could be analysed in a similar way. Our understanding of the LT relation would be much improved if submm fluxes could be determined for these galaxies with known moderate redshifts and radio and far‐IR flux densities.…”

Section: Photometric Redshiftsmentioning

confidence: 99%

Submillimetre and far-infrared spectral energy distributions of galaxies: the luminosity-temperature relation and consequences for photometric redshifts

Blain

Barnard²,

Chapman

2003

Monthly Notices of the Royal Astronomical Society

215

250

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The spectral energy distributions (SEDs) of dusty high‐redshift galaxies are poorly sampled in frequency and spatially unresolved. Their form is crucially important for estimating the large luminosities of these galaxies accurately, for providing circumstantial evidence concerning their power sources, and for estimating their redshifts in the absence of spectroscopic information. We discuss the suite of parameters necessary to describe their SEDs adequately without introducing unnecessary complexity. We compare directly four popular descriptions, explain the key degeneracies between the parameters in each when confronted with data, and highlight the differences in their best‐fitting values. Using one representative SED model, we show that fitting to even a large number of radio, submillimetre and far‐infrared (far‐IR) continuum colours provides almost no power to discriminate between the redshift and dust temperature of an observed galaxy, unless an accurate relationship with a tight scatter exists between luminosity and temperature for the whole galaxy population. We review our knowledge of this luminosity–dust temperature relation derived from three galaxy samples, to better understand the size of these uncertainties. Contrary to recent claims, we stress that far‐IR‐based photometric redshifts are unlikely to be sufficiently accurate to impose useful constraints on models of galaxy evolution: finding spectroscopic redshifts for distant dusty galaxies will remain essential.

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“…For the dusty sub‐sample, the observed mean radio emission is likely associated with starburst activity (e.g. LIGs; Sadler et al 2002). Assuming this is the case, the mean radio luminosity of the dusty sub‐population corresponds to an average SFR (0.1–100 M ⊙ ) ≈ 25 M ⊙ yr −1 , adopting the calibration of Bell (2003).…”

Section: Radio Stackingmentioning

confidence: 99%

The Phoenix Deep Survey: the star formation rates and the stellar masses of extremely red objects

Georgakakis¹,

Hopkins²,

Afonso³

et al. 2006

Monthly Notices of the Royal Astronomical Society

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We estimate the star formation rates and the stellar masses of the extremely red objects (EROs) detected in a ≈180 arcmin2Ks‐band survey (Ks ≈ 20 mag). This sample is complemented by sensitive 1.4‐GHz radio observations (12 μJy 1σ rms) and multiwaveband photometric data (UBVRIJ) as part of the Phoenix Deep Survey. For bright K < 19.5 mag EROs in this sample (I−K > 4 mag; total of 177), we use photometric methods to discriminate dust‐enshrouded active systems from early‐type galaxies and to constrain their redshifts. Radio stacking is then employed to estimate mean radio flux densities of ≈8.6 (3σ) and 6.4 μJy (2.4σ) for the dusty and early‐type sub‐samples, respectively. Assuming that dust‐enshrouded active EROs are powered by star formation, the above radio flux density at the median redshift of z = 1 translates to a radio luminosity of L1.4 = 4.5 × 1022 W Hz‐1 and a star formation rate of SFR = 25 M⊙ yr−1. Combining this result with photometric redshift estimates, we find a lower limit to the star formation rate density of 0.02 ± 0.01 M⊙ yr−1 Mpc−3 for the K < 19.5 mag dusty EROs in the range z = 0.85–1.35. Comparison with the star formation rate density estimated for previous ERO samples (with similar selection criteria) using optical emission lines, suffering dust attenuation, suggests a mean dust reddening of at least E(B−V) ≈ 0.5 for this population. We further use the Ks‐band luminosity as proxy to stellar mass and argue that the dust‐enshrouded starburst EROs in our sample are massive systems, M ≳ 5 × 1010 M⊙. We also find that EROs represent a sizable fraction (about 50 per cent) of the number density of galaxies more massive than M = 5 × 1010 M⊙ at z ≈ 1, with almost equal contributions from dusty and early‐type systems. Similarly, we find that EROs contribute about half of the mass density of the Universe at z ≈ 1 (with almost equal contributions from dusty and early types), after taking into account incompleteness because of the magnitude limit K = 19.5 mag.

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Abstracts of general addresses [Dr. Michael E. Sadler]

Cited by 8 publications

References 0 publications

On the fundamental dichotomy in the local radio-AGN population: accretion, evolution and host galaxy properties

On the fundamental dichotomy in the local radio-AGN population: accretion, evolution and host galaxy properties

Submillimetre and far-infrared spectral energy distributions of galaxies: the luminosity-temperature relation and consequences for photometric redshifts

The Phoenix Deep Survey: the star formation rates and the stellar masses of extremely red objects

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