942 research outputs found
The connection between star formation and supermassive Black Hole activity in the local Universe
We present a study of the active galactic nucleus (AGN) activity in the local
Universe (z < 0.33) and its correlation with the host galaxy properties,
derived from a Sloan Digital Sky Survey (SDSS DR8) sample with spectroscopic
star-formation rate (SFR) and stellar mass ()
determination. To quantify the level of AGN activity we used X-ray information
from the XMM-Newton Serendipitous Source Catalogue (3XMM DR8). Applying
multiwavelength AGN selection criteria (optical BPT-diagrams, X-ray/optical
ratio etc) we found that 24% of the detected sources are efficiently-accreting
AGN with moderate-to-high X-ray luminosity, which are twice as likely to be
hosted by star-forming galaxies than by quiescent ones. The distribution of the
specific Black Hole accretion rate (sBHAR, ) shows
that nuclear activity in local, non-AGN dominated galaxies peaks at very low
accretion rates () in all
stellar mass ranges. However, we observe systematically larger values of sBHAR
for galaxies with active star-formation than for quiescent ones, as well as an
increase of the mean with SFR for both star-forming
and quiescent galaxies. These findings confirm the decreased level of AGN
activity with cosmic time and are consistent with a scenario where both
star-formation and AGN activity are fuelled by a common gas reservoir.Comment: 20 pages, 20 figures, accepted for publication in MNRA
Evidence for a mass-dependent AGN Eddington ratio distribution via the flat relationship between SFR and AGN luminosity
The lack of a strong correlation between AGN X-ray luminosity (L X ; a proxy for AGN power) and the star formation rate (SFR) of their host galaxies has recently been attributed to stochastic AGNvariability. Studies using population synthesis models have incorporated this by assuming a broad, universal (i.e. does not depend on the host galaxy properties) probability distribution for AGN specific X-ray luminosities (i.e. the ratio of L X to host stellar mass; a common proxy for Eddington ratio). However, recent studies have demonstrated that this universal Eddington ratio distribution fails to reproduce the observed X-ray luminosity functions beyond z ~ 1.2. Furthermore, empirical studies have recently shown that the Eddington ratio distribution may instead depend upon host galaxy properties, such as SFR and/or stellarmass. To investigate this further, we develop a population synthesis model in which the Eddington ratio distribution is different for star-forming and quiescent host galaxies. We showthat, although this model is able to reproduce the observed X-ray luminosity functions out to z ~ 2, it fails to simultaneously reproduce the observed flat relationship between SFR and X-ray luminosity. We can solve this, however, by incorporating a mass dependency in the AGN Eddington ratio distribution for starforming host galaxies. Overall, our models indicate that a relative suppression of low Eddington ratios (λ Edd < ~0.1) in lower mass galaxies (M * < ~10 10-11 Mâ) is required to reproduce both the observed X-ray luminosity functions and the observed flat SFR/X-ray relationship
TRINITY II: The Luminosity-dependent Bias of the Supermassive Black Hole Mass--Galaxy Mass Relation for Bright Quasars at
Using recent empirical constraints on the dark matter
halo--galaxy--supermassive black hole (SMBH) connection from , we infer
how undermassive, typical, and overmassive SMBHs contribute to the quasar
luminosity function (QLF) at . We find that beyond erg/s, the QLF is dominated by SMBHs that are at least
0.3 dex above the median relation. The QLF is dominated
by typical SMBHs (i.e., within dex around the
relation) at erg/s. At , the
intrinsic relation for all SMBHs is slightly steeper than the
scaling, with a similar normalization at . We
also predict the relation for bright quasars selected by
different bolometric luminosity thresholds, finding very good agreement with
observations. For quasars with ()
erg/s, the scaling relation is shifted upwards by (1.0) dex for
galaxies. To accurately measure the intrinsic
relation, it is essential to include fainter quasars with erg/s. At high redshifts, low-luminosity quasars are thus the
best targets for understanding typical formation paths for SMBHs in galaxies.Comment: 5 pages, 3 figures. Submitted to MNRAS Letters. Comments welcome
The Nustar Extragalactic Surveys: Initial Results and Catalog from the Extended Chandra Deep Field South
We present initial results and the source catalog from the NuSTAR survey of the Extended Chandra Deep Field South (hereafter, ECDFS) - currently the deepest contiguous component of the NuSTAR extragalactic survey program. The survey covers the full ~30 arcmin x 30 arcmin area of this field to a maximum depth of ~360 ks (~220 ks when corrected for vignetting at 3-24 keV), reaching sensitivity limits of ~1.3 x 10^-14 erg/cm2/s (3-8 keV), ~3.4 x 10^-14 erg/cm2/s (8-24 keV) and ~3.0 x 10^-14 erg/cm2/s (3-24 keV). Fifty four (54) sources are detected over the full field, although five of these are found to lie below our significance threshold once contaminating flux from neighboring (i.e., blended) sources is taken into account. Of the remaining 49 that are significant, 19 are detected in the 8-24 keV band. The 8-24 keV to 3-8 keV band ratios of the twelve sources that are detected in both bands span the range 0.39-1.7, corresponding to a photon index range of Gamma ~ 0.5-2.3, with a median photon index of 1.70 +/- 0.52. The redshifts of the 49 sources in our main sample span the range z = 0.21-2.7, and their rest-frame 10-40 keV luminosities (derived from the observed 8-24 keV fluxes) span the range L(10-40 keV) ~ (0.7-300) x 10^43 erg/s, sampling below the knee of the X-ray luminosity function out to z ~ 0.8-1. Finally, we identify one NuSTAR source that has neither a Chandra nor an XMM-Newton counterpart, but that shows evidence of nuclear activity at infrared wavelengths, and thus may represent a genuine, new X-ray source detected by NuSTAR in the ECDFS
Trinity I: self-consistently modelling the dark matter haloâgalaxyâsupermassive black hole connection from z = 0â10
TRINITY IV: Predictions for Supermassive Black Holes at
We present predictions for the high-redshift halo-galaxy-supermassive black
hole (SMBH) connection from the TRINITY model. Constrained by a comprehensive
compilation of galaxy () and SMBH datasets (), TRINITY finds: 1) The number of SMBHs with in
the observable Universe increases by six orders of magnitude from to
, and by another factor of from to ; 2) The
SMBHs at live in haloes with ; 3) the new JWST AGNs at are broadly consistent with the median SMBH mass-galaxy mass
relation for AGNs from TRINITY; 4) Seeds from runaway mergers in nuclear star
clusters are viable progenitors for the SMBHs in GN-z11 () and
CEERS_1019 (); 5) quasar luminosity functions from wide area
surveys by, e.g., Roman and Euclid, will reduce uncertainties in the
SMBH mass-galaxy mass relation by up to dex.Comment: 15 pages, 12 figures, submitted to MNRAS. Questions and comments are
welcome
Acupuncture Point Localization Varies Among Acupuncturists
Background: Studies assessing the point-specific effect of acupuncture or the characteristics of acupuncture points (APs) tend to yield inconclusive results. In order to identify a possible confounding factor, we aimed to examine the variability in AP localization by means of a survey. Material and Methods: Attendees of the 14th ICMART (International Council of Medical Acupuncture and Related Techniques) congress as well as DAGfA (German Medical Society of Acupuncture) lecturers and students were asked to locate and mark the APs LI 10 and TH 5 on a research assistant's arm. Identified points were transferred into a coordinate system, and the respective bivariate distribution function was calculated. Additionally, participants filled out a questionnaire about their acupuncture education and experience, the acupuncture style and point localization techniques used most frequently, and their estimation of the size of an AP. Results: The areas of the ellipses, theoretically containing 95% of AP localizations, varied between 44.49 and 5.18 cm(2). The largest distance between 2 identified points was 8.45 cm for LI 10 and 5.3 cm for TH 5. Apart from being trained at the same school, no other factor could be identified that determined the variability in AP localization. Conclusion: Our results indicate that congruity of AP localization among experienced acupuncturists might be low. Although there are some limitations to our results, this possible bias should be taken into account when conducting acupuncture trials and interpreting results of previous acupuncture studies
Hypoxia-driven metabolic reprogramming of adipocytes fuels cancer cell proliferation
OBJECTIVE: Obesity increases the risk of certain cancers, especially tumours that reside close to adipose tissue (breast and ovarian metastasis in the omentum). The obesogenic and tumour micro-environment share a common pathogenic feature, oxygen deprivation (hypoxia). Here we test how hypoxia changes the metabolome of adipocytes to assist cancer cell growth. METHODS: Human and mouse breast and ovarian cancer cell lines were co-cultured with human and mouse adipocytes respectively under normoxia or hypoxia. Proliferation and lipid uptake in cancer cells were measured by commercial assays. Metabolite changes under normoxia or hypoxia were measured in the media of human adipocytes by targeted LC/MS. RESULTS: Hypoxic cancer-conditioned media increased lipolysis in both human and mouse adipocytes. This led to increased transfer of lipids to cancer cells and consequent increased proliferation under hypoxia. These effects were dependent on HIF1α expression in adipocytes, as mouse adipocytes lacking HIF1α showed blunted responses under hypoxic conditions. Targeted metabolomics of the human Simpson-Golabi-Behmel syndrome (SGBS) adipocytes media revealed that culture with hypoxic-conditioned media from non-malignant mammary epithelial cells (MCF10A) can alter the adipocyte metabolome and drive proliferation of the non-malignant cells. CONCLUSION: Here, we show that hypoxia in the adipose-tumour microenvironment is the driving force of the lipid uptake in both mammary and ovarian cancer cells. Hypoxia can modify the adipocyte metabolome towards accelerated lipolysis, glucose deprivation and reduced ketosis. These metabolic shifts in adipocytes could assist both mammary epithelial and cancer cells to bypass the inhibitory effects of hypoxia on proliferation and thrive
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