172 research outputs found
Light, medium-weight or heavy? The nature of the first supermassive black hole seeds
No full textObservations of hyper-luminous quasars at z>6 reveal the rapid growth of supermassive black holes (SMBHs >10^9 m M_{odot}) whose origin is still difficult to explain. Their progenitors may have formed as remnants of massive, metal free stars (light seeds), via stellar collisions (medium-weight seeds) and/or massive gas clouds direct collapse (heavy seeds). In this work we investigate for the first time the relative role of these three seed populations in the formation of z>6 SMBHs within an Eddington-limited gas accretion scenario. To this aim, we implement in our semi-analytical data-constrained model a statistical description of the spatial fluctuations of Lyman-Werner (LW) photo-dissociating radiation and of metal/dust enrichment. This allows us to set the physical conditions for BH seeds formation, exploring their relative birth rate in a highly biased region of the Universe at z>6. We find that the inclusion of medium-weight seeds does not qualitatively change the growth history of the first SMBHs: although less massive seeds (<10^3 m M_odot) form at a higher rate, the mass growth of a SMBH at z<15 is driven by efficient gas accretion (at a sub-Eddington rate) onto its heavy progenitors (). This conclusion holds independently of the critical level of LW radiation and even when medium-weight seeds are allowed to form in higher metallicity galaxies, via the so-called super-competitive accretion scenario. Our study suggests that the genealogy of SMBHs is characterized by a rich variety of BH progenitors, which represent only a small fraction (< 10 - 20%) of all the BHs that seed galaxies at z > 15
Graphium sarpedon subsp. sirkari Page & Treadaway 2013
No full textGraphium sarpedon sirkari Page & Treadaway, 2013 INDIA: 1♂, HOLOTYPE [illustration], Shillong, Khasi Hills, Assam, N. India, April–June 1968, leg. S. K. Sirkar. [SMF]. MYANMAR: 1♂, Hkasi (1,050 m), Tarung Hka River, N. Sagaing State, 2007-VII-14, Prasobsuk Sukkit leg. [AMC]; 1♂, same locality, 2007-VIII-4, Prasobsuk Sukkit leg. [AMC]; 1♂, same locality, 2008-VII-25, Prasobsuk Sukkit leg. [AMC]; 1♂, between Pangmandim & Gawai, Mayhka River, N. Kachin State, 1996-IX-14, Prasobsuk Sukkit leg. [AMC]; 1♂, Chudu Razi Hills, east of Kawnglanghpu, N.E. Kachin State, 2004-VI-24, Prasobsuk Sukkit leg. [AMC]; 2♂♂, same locality, 2005-VI-26, Prasobsuk Sukkit leg. [AMC]; 1♂, same locality, 2006-VII-17, Prasobsuk Sukkit leg. [AMC]; 2♂♂, same locality, 2007-VII-5, Prasobsuk Sukkit leg. [AMC]; 1♂, same locality, 2008-VI-24, Prasobsuk Sukkit leg. [AMC]. CHINA: 1♂, Fugong, N.W. Yunnan, 2012-VII-17, Prasobsuk Sukkit leg. [AMC].Published as part of Cotton, Adam M., Doleck, Tenzing, Zhang, Xin, Inayoshi, Yutaka, Lohman, David J. & Hu, Shao-Ji, 2022, Graphium septentrionicolus Page & Treadaway, 2013 (Lepidoptera: Papilionidae) is a distinct species, pp. 211-224 in Zootaxa 5154 (2) on page 223, DOI: 10.11646/zootaxa.5154.2.6, http://zenodo.org/record/664141
Graphium septentrionicolus Page & Treadaway 2013, stat. nov.
No full textGraphium septentrionicolus Page & Treadaway, 2013 stat. nov. INDIA: 1♂, HOLOTYPE [illustration], Nowgang, Assam, 1964-IV-14, C. G. Treadaway leg. [SMF]. MYANMAR: 1♂, Hkasi (1,050 m), Tarung Hka River, N. Sagaing State, 2007-VII-2, Prasobsuk Sukkit leg. [AMC]; 1♂, same locality, 2008-IV-22, Prasobsuk Sukkit leg. [AMC]; 1♂, same locality, 2008-IV-25, Prasobsuk Sukkit leg. [AMC]; 6♂♂, between Pangmandim & Gawai, Mayhka River, N. Kachin State, 1996-VII-20-27, Prasobsuk Sukkit leg. [AMC]; 1♂, Dasu Long, east of Renam, N.E. Kachin State, 1996-VI-21, Prasobsuk Sukkit leg. [AMC]; 1♂, same locality, 2005-V-23, Prasobsuk Sukkit leg. [AMC]; 1♂, same locality, 2006-V-1, Prasobsuk Sukkit leg. [AMC]; 1♂, Chudu Razi Hills, east of Kawnglanghpu, N.E. Kachin State, 2005-VII-27, Prasobsuk Sukkit leg. [AMC]; 1♂, same locality, 2006-VII-15, Prasobsuk Sukkit leg. [AMC]; 1♂, same locality, 2007-VI-3, Prasobsuk Sukkit leg. [AMC]; 1♂, same locality, 2008-IV-26, Prasobsuk Sukkit leg. [AMC]; 1♂, same locality, 2008-VI-10, Prasobsuk Sukkit leg. [AMC]; 1♂, Mairudam, N.E. Kachin State, 2005-VIII-1, Prasobsuk Sukkit leg. [AMC]. CHINA: 1♂, Duoxiongla valley, Metok, S. Tibet, 2012-VII–22-VIII-10, Yang Yang leg. [AMC]; 5♂♂, Beibeng, Metok, S. Tibet, 2016-IV–23-V-1, Lu Ji leg. [AMC]; 2♂♂, Tongbiguan (1,000 m), Yingjiang, Yunnan, 2017-III-26; Wei-Zong Yang leg. [SJH]; 1♂, Fugong, N.W. Yunnan, 2006-VIII-13, Prasobsuk Sukkit leg. [AMC]. LAOS: 1♂, Phou Phan, Sam Neua, Houaphanh Province, 2005-III-7, Khamboun Sengheuangsomphou leg. [AMC]. VIETNAM: 1♂, Sapa, Lao Cai Province, 2007-V, local catcher leg. [AMC]; 2♂♂, Ngoc Linh (2,400 m), Kon Tum Province, 2021-IV, local catcher leg. [KS].Published as part of Cotton, Adam M., Doleck, Tenzing, Zhang, Xin, Inayoshi, Yutaka, Lohman, David J. & Hu, Shao-Ji, 2022, Graphium septentrionicolus Page & Treadaway, 2013 (Lepidoptera: Papilionidae) is a distinct species, pp. 211-224 in Zootaxa 5154 (2) on page 223, DOI: 10.11646/zootaxa.5154.2.6, http://zenodo.org/record/664141
Systematic Broad-band X-ray Study of super-Eddington Accretion onto Supermassive Black Holes. I. X-ray Continuum
No full textWe present the first systematic broad-band X-ray study of super-Eddington
accretion onto SMBHs with simultaneous {\it NuSTAR} and {\it XMM-Newton} or
{\it Swift}/XRT observations of a sample of 8 super-Eddington accreting AGN
with Eddington ratio . We find that the SEAMBHs show a
steep primary continuum slope as expected for sources accreting in the super
Eddington regime, mostly dominated by relativistic reflection. The Iron
K emission lines of the sources of our sample show relativistic
broadening. In addition the equivalent widths of the narrow components of the
Iron K lines follow the 'X-ray Baldwin' effect, also known as the
'Iwasawa-Taniguchi' effect. We found a statistically significant correlation
between the photon-index of the primary power-law and the Eddington ratio,
consistent with past studies. Moreover, as expected for super-Eddington
sources, the median value of the reflection fraction of the sources we analysed
is a factor higher than the median reflection fraction value of the
type\,1 AGN from the BASS sample. We are able to estimate the coronal
temperature for three sources of our sample: Mrk\,382 (\,keV),
PG\,0026+129 (\,keV) and IRAS\,04416+1215 (\,keV). Looking at
the position of the SEAMBHs sources of our sample in the
compactness-temperature diagram it appears that in super-Eddington AGN, as for
lower Eddington ratio AGN, the X-ray corona is controlled by pair production
and annihilation.Comment: Accepted for publication in Monthly Notices of the Royal Astronomical
Societ
Extremely Dense Gas around Little Red Dots and High-redshift Active Galactic Nuclei: A Nonstellar Origin of the Balmer Break and Absorption Features
No full textThe James Webb Space Telescope (JWST) has uncovered low-luminosity active galactic nuclei (AGNs) at high redshifts of z ≳ 4–7, powered by accreting black holes with masses of ∼10 ^6−8 M _⊙ . One remarkable distinction of these JWST-identified AGNs, compared to their low-redshift counterparts, is that at least ∼20% of them present H α and/or H β absorption, which must be associated with extremely dense (≳10 ^9 cm ^−3 ) gas in the broad-line region or its immediate surroundings. These Balmer absorption features unavoidably imply the presence of a Balmer break caused by the same dense gas. In this Letter, we quantitatively demonstrate that a Balmer break can form in AGN spectra without stellar components, when the accretion disk is heavily embedded in dense neutral gas clumps with densities of ∼10 ^9−11 cm ^−3 , where hydrogen atoms are collisionally excited to the n = 2 states and effectively absorb the AGN continuum at the bluer side of the Balmer limit. The nonstellar origin of a Balmer break offers a potential solution to the large stellar masses and densities inferred for little red dots (LRDs) when assuming that their continuum is primarily due to stellar light. Our calculations indicate that the observed Balmer absorption blueshifted by a few hundred km s ^−1 , which suggests the presence of dense outflows in the nucleus at rates exceeding the Eddington value. Other spectral features such as higher equivalent widths of broad H α emission and presence of O i lines observed in high-redshift AGNs including LRDs align with the predicted signatures of a dense super-Eddington accretion disk
Redox characteristics variations in the cation-ordered perovskite oxides BaLnMn(2)O(5+delta) (Ln = Y, Gd, Nd, and La) and Ca2Al1-xGaxMnO5+delta (0 <= x <= 1)
No full textTwo series of manganese-based oxygen storage materials, BaLnMn(2)O(5+delta) (Ln = Y, Gd, Nd, and La) and Ca2Al1-xGaxMnO5+delta (0 <= x <= 1), were synthesized and characterized to clarify cationic substitution effects on the oxygen intake/release behaviors of these materials. The thermogravimetric data revealed that the isovalent substitutions neighboring the active sites for oxygen intake/release are very effective. For BaLnMn(2)O(5+)delta, fully-reduced delta approximate to 0 products with larger Ln ions showed oxygen intake starting at lower temperatures in flowing O-2 gas, resulting in a systematic relationship between the onset temperature and the ionic radius of Ln(3+). Furthermore, the delta vs. P(O-2) plots at 700 degrees C indicated a systematic trend: the larger the ionic size of Ln(3+) is, the larger oxygen contents the Ln-products exhibit. For Ca2Al1-x-GaxMnO5+delta , on the other hand, the temperature-induced oxygen intake/release characteristics appeared to be influenced by Ga-for-Al substitution, where the onset temperatures of oxygen release (upon heating) and oxygen intake (upon cooling) are decreased with the increasing Ga content (x)
LASER-MICROWAVE DOUBLE RESONANCE SPECTROSCOPY AND STARK LAMB-DIP SPECTROSCOPY OF THE BAND OF
No full text(1) W.L. Meerts and I. Ozier. J. Chem. Phys. 75, 596 - 603 (1981).Author Institution: Department of Chemistry, Faculty of ScienceThe laser-microwave double resonance (LMDR) spectroscopy with intense electric field was applied to the band of . The dipole moments and polarizability anisotropies in the ground and states were determined as follows, where three times of standard deviations are in parentheses. The dipole moment in the ground state agrees with the result by molecular beam electric resonance, ). The polarizability anisotropies agree with the sum of the electronic polarizability anisotropy obtained from Kerr effect and the contribution of the vibrational Stark effect. The (2,-1) interaction in the state was found to give remarkable perturbations to some rotational levels under the electric field. A new electric field dependent interaction of the (2,-1) type was found to give observable effects. The constants for this interaction as well as for the ordinary (2,-1) interaction were determined. The sign of the l-type doubling constant was determined by means of double resonance experiment. Other molecular constants were also well determined by LMDR and Stark Lamb-dip spectroscopy
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