Fe<scp>ii</scp>/Mg<scp>ii</scp>Emission‐Line Ratios of QSOs. II.<i>z</i>&gt; 6 Objects

Iwamuro, Fumihide; Kimura, Masahiko; Eto, Shigeru; Maihara, Toshinori; Motohara, Kentaro; Yoshii, Yuzuru; Doi, Mamoru

doi:10.1086/423610

Cited by 59 publications

(74 citation statements)

References 20 publications

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“…1, solar or super-solar metallicities are common in quasars up to high redshifts. This does not only refer to so-called "α-elements" being rapidly synthesized in short-lived massive stars but also to iron (e.g., Iwamuro et al 2004;Kurk et al 2007;Sameshima et al 2009), carbon (e.g., Jiang et al 2007;Juarez et al 2009), and, even more importantly, nitrogen (Hamann & Ferland 1999;De Breuck et al 2000;Vernet et al 2001;Hamann et al 2002;Nagao et al 2006;Matsuoka et al 2009), with 14 N being mainly a secondary nucleus produced by CNO burning just like 13 C. A possible explanation for the contradictory results obtained at or near optical wavelengths and the microwave data presented here may be different locations. It is well possible that mainly secondary nuclei like 13 C and 14 N are enriched close to the quasar, in the Broad and Narrow Line Regions and in outflows originating from the active galactic nucleus (AGN).…”

Section: 3mentioning

confidence: 99%

Weak¹³CO in the Cloverleaf quasar: evidence for a young, early generation starburst

Henkel¹,

Downes

Weiß³

et al. 2010

A&A

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Observations of 12 CO at high redshift indicate rapid metal enrichment in the nuclear regions of at least some galaxies in the early universe. However, the enrichment may be limited to nuclei that are synthesized by short-lived massive stars, excluding classical "secondary" nuclei like 13 C. Testing this idea, we used the IRAM Interferometer to tentatively detect the 13 CO J = 3 → 2 line at a level of 0.3 Jy km s −1 toward the Cloverleaf quasar at z = 2.5. This is the first observational evidence for 13 C at high redshift. The 12 CO/ 13 CO J = 3 → 2 luminosity ratio is with 40 +25 −8 much higher than ratios observed in molecular clouds of the Milky Way and in the ultraluminous galaxy Arp 220, but may be similar to that observed toward NGC 6240. Large Velocity Gradient models simulating seven 12 CO transitions and the 13 CO line yield 12 CO/ 13 CO abundance ratios in excess of 100. It is possible that the measured ratio is affected by a strong submillimeter radiation field, which reduces the contrast between the 13 CO line and the background. It is more likely, however, that the ratio is caused by a real deficiency of 13 CO. This is already apparent in local ultraluminous galaxies and may be even more severe in the Cloverleaf because of its young age ( < ∼ 2.5 Gyr). A potential conflict with optical data, indicating high abundances also for secondary nuclei in quasars of high redshift, may be settled if the bulk of the CO emission is originating sufficiently far from the active galactic nucleus of the Cloverleaf.

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Section: 3mentioning

confidence: 99%

Weak¹³CO in the Cloverleaf quasar: evidence for a young, early generation starburst

Henkel¹,

Downes

Weiß³

et al. 2010

A&A

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“…Among the most surprising discoveries in this field are the detection of BH masses > 10 9 M (e.g., Barth et al 2003;Willott et al 2003) and the apparent constancy of the observed QSO BLR properties with redshift, even up to z = 6.4 (e.g., Pentericci et al 2002), corresponding to an age of 870 Myr. For example, the Fe ii/Mg ii (Freudling et al 2003;Maiolino et al 2003;Iwamuro et al 2004;Kurk et al 2007, hereafter K07) and N v/C iv (Jiang et al 2007) emission-line ratios observed in the BLR of z > 6 QSOs are as high as that observed in low-redshift objects. Thus, nearsolar metallicity in the centers of some of the earliest systems and accretion of > 10 9 solar masses in a central BH can be attained in less than 1 Gyr.…”

Section: Introductionmentioning

confidence: 99%

NEAR-INFRARED SPECTROSCOPY OF SDSS J0303 – 0019: A LOW-LUMINOSITY, HIGH-EDDINGTON-RATIO QUASAR ATz∼ 6

Kurk

Walter

Fan³

et al. 2009

ApJ

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We present sensitive near-infrared (NIR) VLT ISAAC spectroscopic observations of the z = 6.08 quasar SDSS J030331.40-001912.9. This quasi-stellar object (QSO) is more than a magnitude fainter than other QSOs at z ∼ 6 for which NIR spectroscopy has been obtained to date and is therefore presumably more representative of the QSO population at the end of cosmic reionization. Combining rest-frame UV continuum luminosity with the width measurements of the Mg ii and C iv lines, we derive a black hole mass of 2 +1.0 −0.5 × 10 8 M , the lowest mass observed for z ∼ 6 QSOs to date, and derive an Eddington ratio of 1.6 +0.4 −0.6 , among the highest value derived for QSOs at any redshift. The Spitzer 24 μm nondetection of this QSO does not leave space for a significant hot dust component in its optical/NIR spectral energy distribution, in common with one other faint QSO at z = 6, but in contrast to more than 20 more z = 6 QSOs and all known lower redshift QSOs with sufficiently deep multiwavelength photometry. We conclude that we have found evidence for differences in the intrinsic properties of at least one z ∼ 6 QSO as compared to the lower redshift population.

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“…Their results show an increase in the scatter of the measured Fe ii/Mg ii line ratios as a function of the redshift. One possible way to interpret the increase in the scatter is that some objects are observed such a short time after the initial starburst that the BLR is not yet fully enriched with Fe (Iwamuro et al 2004). Nonetheless, several possible systematics related to the adopted fitting procedure could potentially be the cause of the observed discrepancies between different authors: the iron template employed, the wavelength limits over which the template is integrated, the wavelength range over which the template is actually fitted, and the wavelength coverage and signal-to-noise ratio (S/N) of the spectra used.…”

Section: Introductionmentioning

confidence: 99%

EVIDENCE FOR NON-EVOLVING Fe II/Mg II RATIOS IN RAPIDLY ACCRETINGz∼ 6 QSOs

Rosa

Decarli

Walter

et al. 2011

ApJ

224

265

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Quasars (QSOs) at the highest known redshift (z ∼ 6) are unique probes of the early growth of supermassive black holes (BHs). Until now, only the most luminous QSOs have been studied, often one object at a time. Here we present the most extensive consistent analysis to date of 4 < z < 6.5 QSOs with observed near-infrared spectra, combining three new z ∼ 6 objects from our ongoing Very Large Telescope-Infrared Spectrometer And Array Camera program with nineteen sources from the literature. The new sources extend the existing Sloan Digital Sky Survey (SDSS) sample toward the faint end of the QSO luminosity function. Using a maximum likelihood fitting routine optimized for our spectral decomposition, we estimate the BH mass (M BH ), the Eddington ratio (defined as L bol /L Edd ), and the Fe ii/Mg ii line ratio, a proxy for the chemical abundance, to characterize both the central object and the broad-line region gas. The QSOs in our sample host BHs with masses of ∼10 9 M that are accreting close to the Eddington luminosity, consistent with earlier results. We find that the distribution of observed Eddington ratios is significantly different than that of a luminosity-matched comparison sample of SDSS QSOs at lower redshift (0.35 < z < 2.25): the average log(L bol /L Edd ) = −0.37 (L bol /L Edd ∼ 0.43) with a scatter of 0.20 dex for the z > 4 sample and the log(L bol /L Edd ) = −0.80 (L bol /L Edd ∼ 0.16) with a scatter of 0.24 dex for the 0.35 < z < 2.25 sample. This implies that, at a given luminosity, the M BH at high-z is typically lower than the average M BH of the lower-redshift population, i.e., the z > 4 sources are accreting significantly faster than the lower-redshift ones. We show that the derived Fe ii/Mg ii ratios depend sensitively on the analysis performed: our self-consistent, homogeneous analysis significantly reduces the Fe ii/Mg ii scatter found in previous studies. The measured Fe ii/Mg ii line ratios show no sign of evolution with cosmic time in the redshift range 4 < z < 6.5. If the Fe ii/Mg ii line ratio is used as a secondary proxy of the Fe/Mg abundance ratio, this implies that the QSOs in our sample have undergone a major episode of Fe enrichment in the few 100 Myr preceding the cosmic age at which they are observed.

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Feii/MgiiEmission‐Line Ratios of QSOs. II.z> 6 Objects

Cited by 59 publications

References 20 publications

Weak¹³CO in the Cloverleaf quasar: evidence for a young, early generation starburst

Weak¹³CO in the Cloverleaf quasar: evidence for a young, early generation starburst

NEAR-INFRARED SPECTROSCOPY OF SDSS J0303 – 0019: A LOW-LUMINOSITY, HIGH-EDDINGTON-RATIO QUASAR ATz∼ 6

EVIDENCE FOR NON-EVOLVING Fe II/Mg II RATIOS IN RAPIDLY ACCRETINGz∼ 6 QSOs

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Feii/MgiiEmission‐Line Ratios of QSOs. II.z> 6 Objects

Cited by 59 publications

References 20 publications

Weak13CO in the Cloverleaf quasar: evidence for a young, early generation starburst

Weak13CO in the Cloverleaf quasar: evidence for a young, early generation starburst

NEAR-INFRARED SPECTROSCOPY OF SDSS J0303 – 0019: A LOW-LUMINOSITY, HIGH-EDDINGTON-RATIO QUASAR ATz∼ 6

EVIDENCE FOR NON-EVOLVING Fe II/Mg II RATIOS IN RAPIDLY ACCRETINGz∼ 6 QSOs

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Weak¹³CO in the Cloverleaf quasar: evidence for a young, early generation starburst

Weak¹³CO in the Cloverleaf quasar: evidence for a young, early generation starburst