Browsing by Author "Yang, G."

Now showing 1 - 15 of 15
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    Black Hole Growth Is Mainly Linked to Host-galaxy Stellar Mass Rather Than Star Formation Rate
    (2017) Wang, J.; Yang, G.; Chen, C.; Vito, F.; Brandt, W.; Alexander, D.; Luo, B.; Sun, M.; Xue, Y.; Bauer, Franz Erik; Koekemoer, A.; Lehmer, B.; Liu, T.; Schneider, D.; Shemmer, O.; Trump J.; Vignali, C.
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    Does black hole growth depend fundamentally on host-galaxy compactness?
    (2019) Ni, Q.; Yang, G.; Brandt, W. N.; Alexander, D. M.; Chen, C-T J.; Luo, B.; Vito, F.; Xue, Y. Q.
    Possible connections between central black hole (BH) growth and host-galaxy compactness have been found observationally, which may provide insight into BH-galaxy coevolution: compact galaxies might have large amounts of gas in their centres due to their high mass-to-size ratios, and simulations predict that high central gas density can boost BH accretion. However, it is not yet clear if BH growth is fundamentally related to the compactness of the host galaxy, due to observational degeneracies between compactness, stellar mass (M-star) and star formation rate (SFR). To break these degeneracies, we carry out systematic partial-correlation studies to investigate the dependence of sample-averaged BH accretion rate ((BHAR) over bar) on the compactness of host galaxies, represented by the surface-mass density, Sigma(e), or the projected central surface-mass density within 1 kpc, Sigma(1). We utilize 8842 galaxies with H < 24.5 in the five CANDELS fields at z = 0.5-3. We find that <(BHAR)over bar> does not significantly depend on compactness when controlling for SFR or M-star among bulge-dominated galaxies and galaxies that are not dominated by bulges, respectively. However, when testing is confined to star-forming galaxies at z = 0.5-1.5, we find that the (BHAR) over bar-Sigma(1) relation is not simply a secondary manifestation of a primary (BHAR) over bar -M-star relation, which may indicate a link between BH growth and the gas density within the central 1 kpc of galaxies.
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    Does black-hole growth depend on the cosmic environment?
    (2018) Yang, G.; Brandt, W.N.; Darvish, B.; Chen, C.T.; Vito, F.; Alexander, D.M.; Bauer, Franz Erik; Trump, J.R.
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    Evident black hole-bulge coevolution in the distant universe
    (2019) Yang, G.; Brandt, W. N.; Alexander, D. M.; Chen, C. -T. J.; Ni, Q.; Vito, F.; Zhu, F. -F.
    Observations in the local universe show a tight correlation between the masses of supermassive black holes (SMBHs; M-BH) and host-galaxy bulges (M-bulge), suggesting a strong connection between SMBH and bulge growth. However, direct evidence for such a connection in the distant universe remains elusive. We have studied sample-averaged SMBH accretion rate ((BHAR) over bar) for bulge-dominated galaxies at z = 0.5-3. While previous observations found (BHAR) over bar is strongly related to host-galaxy stellar mass (M-star) for the overall galaxy population, our analyses show that, for the bulge-dominated population, (BHAR) over bar is mainly related to SFR rather than M-star. This (BHAR) over bar -SFR relation is highly significant, e.g. 9.0 sigma (Pearson statistic) at z = 0.5-1.5. Such a (BHAR) over bar -SFR connection does not exist among our comparison sample of galaxies that are not bulge dominated, for which M-star appears to be the main determinant of SMBH accretion. This difference between the bulge-dominated and comparison samples indicates that SMBHs only coevolve with bulges rather than the entire galaxies, explaining the tightness of the local M-BH - M-bulge correlation. Our best-fitting (BHAR) over bar -SFR relation for the bulge-dominated sample is log (BHAR) over bar = log SFR - (2.48 +/- 0.05) (solar units). The best-fitting (BHAR) over bar /SFR ratio (10(-2.48)) for bulge-dominated galaxies is similar to the observed M-BH/M-bulge values in the local universe. Our results reveal that SMBH and bulge growth are in lockstep, and thus non-causal scenarios of merger averaging are unlikely the origin of the M-BH-M-bulge correlation. This lockstep growth also predicts that the M-BH-M-bulge relation should not have strong redshift dependence.
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    Extragalactic fast X-ray transient candidates discovered by Chandra (2000-2014)
    (2022) Quirola-Vasquez, J.; Bauer, F. E.; Jonker, P. G.; Brandt, W. N.; Yang, G.; Levan, A. J.; Xue, Y. Q.; Eappachen, D.; Zheng, X. C.; Luo, B.
    Context. Extragalactic fast X-ray transients (FXRTs) are short flashes of X-ray photons of unknown origin that last a few seconds to hours.
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    Extragalactic fast X-ray transient candidates discovered by Chandra (2014-2022)
    (2023) Quirola-Vasquez, J.; Bauer, F. E.; Jonker, P. G.; Brandt, W. N.; Yang, G.; Levan, A. J.; Xue, Y. Q.; Eappachen, D.; Camacho, E.; Ravasio, M. E.; Zheng, X. C.; Luo, B.
    Context. Extragalactic fast X-ray transients (FXTs) are short flashes of X-ray photons of unknown origin that last a few minutes to hours.
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    Long-term x-ray variability of typical active galactic nuclei in the distant universe.
    (2016) Yang, G.; Kim, Sam; Brandt, W N.; Bauer, Franz Erik; Schulze, Steve.; Luo, B.; Xue, Y. Q.; Sun, M. Y.; Zheng, X. C.; Paolillo, M.; Shemmer, O.
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    PHOTOMETRIC REDSHIFTS IN THE HAWAII-HUBBLE DEEP FIELD-NORTH (H-HDF-N)
    (2014) Bauer, Franz Erik; Yang, G.; Xue, Y.; Luo, B.; Brandt, W.; Alexander, D.; Cui, W.; Kong, X.
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    Probing a magnetar origin for the population of extragalactic fast X-ray transients detected by Chandra
    (2024) Quirola-Vasquez, J.; Bauer, F. E.; Jonker, P. G.; Brandt, W. N.; Eappachen, D.; Levan, A. J.; Lopez, E.; Luo, B.; Ravasio, M. E.; Sun, H.; Xue, Y. Q.; Yang, G.; Zheng, X. C.
    Context. Twenty-two extragalactic fast X-ray transients (FXTs) have now been discovered from two decades of Chandra data (analyzing similar to 259 Ms of data), with 17 associated with distant galaxies (greater than or similar to 100 Mpc). Different mechanisms and progenitors have been proposed to explain their properties; nevertheless, after analyzing their timing, spectral parameters, host -galaxy properties, luminosity function, and volumetric rates, their nature remains uncertain. Aims. We interpret a sub -sample of nine FXTs that show a plateau or a fast -rise light curve within the framework of a binary neutron star (BNS) merger magnetar model. Methods. We fit their light curves and derive magnetar (magnetic field and initial rotational period) and ejecta (ejecta mass and opacity) parameters. This model predicts two zones: an orientation -dependent free zone (where the magnetar spin -down X-ray photons escape freely to the observer) and a trapped zone (where the X-ray photons are initially obscured and only escape freely once the ejecta material becomes optically thin). We argue that six FXTs show properties consistent with the free zone and three FXTs with the trapped zone. Results. This sub -sample of FXTs has a similar distribution of magnetic fields and initial rotation periods to those inferred for short gamma -ray bursts, suggesting a possible association. We compare the predicted ejecta emission fed by the magnetar emission (called merger -nova) to the optical and near -infrared upper limits of two FXTs, XRT 141001 and XRT 210423 where contemporaneous optical observations are available. The non -detections place lower limits on the redshifts of XRT 141001 and XRT 210423 of z greater than or similar to 1.5 and greater than or similar to 0.1, respectively. Conclusions. If the magnetar remnants lose energy via gravitational waves (GWs), it should be possible to detect similar objects with the current advanced LIGO detectors out to a redshift z less than or similar to 0.03, while future GW detectors will be able to detect them out to z approximate to 0.5.
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    Revealing the relation between black hole growth and host-galaxy compactness among star-forming galaxies
    (2021) Ni, Q.; Brandt, W. N.; Yang, G.; Leja, J.; Chen, C-T J.; Luo, B.; Matharu, J.; Sun, M.; Vito, F.; Xue, Y. Q.; Zhang, K.
    Recent studies show that a universal relation between black hole (BH) growth and stellar mass (M-*) or star formation rate (SFR) is an oversimplification of BH-galaxy coevolution, and that morphological and structural properties of host galaxies must also be considered. Particularly, a possible connection between BH growth and host-galaxy compactness was identified among star-forming (SF) galaxies. Utilizing approximate to 6300 massive galaxies with I-814W < 24 at z < 1.2 in the Cosmic Evolution Survey (COSMOS) field, we perform systematic partial correlation analyses to investigate how sample-averaged BH accretion rate (BHAR) depends on host-galaxy compactness among SF galaxies, when controlling for morphology and M-* (or SFR). The projected central surface mass density within 1 kpc, Sigma(1), is utilized to represent host-galaxy compactness in our study. We find that the BHAR-Sigma(1) relation is stronger than either the BHAR-M-* or BHAR-SFR relation among SF galaxies, and this BHAR-Sigma(1) relation applies to both bulge-dominated galaxies and galaxies that are not dominated by bulges. This BHAR-Sigma(1) relation among SF galaxies suggests a link between BH growth and the central gas density of host galaxies on the kpc scale, which may further imply a common origin of the gas in the vicinity of the BH and in the central similar to kpc of the galaxy. This BHAR-Sigma(1) relation can also be interpreted as the relation between BH growth and the central velocity dispersion of host galaxies at a given gas content (i.e. gas mass fraction), indicating the role of the host-galaxy potential well in regulating accretion on to the BH.
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    Searching for fast extragalactic X-ray transients in Chandra surveys
    (2019) Yang, G.; Brandt, W. N.; Zhu, S. F.; Bauer, Franz Erik; Luo, B.; Xue, Y. Q.; Zheng, X. C.
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    The 2 Ms Chandra Deep Field-North Survey and the 250 ks Extended Chandra Deep Field-South Survey : Improved Point-Source Catalogs
    (2016) Xue, Y. Q.; Luo, B.; Brandt, W. N.; Alexander, D. M.; Bauer, Franz Erik; Lehmer, B. D.; Yang, G.
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    THE CHANDRA DEEP FIELD-SOUTH SURVEY: 7 MS SOURCE CATALOGS
    (2017) Luo, B.; Brandt, W. N.; Xue, Y. Q.; Lehmer, B.; Alexander, D. M.; Bauer, Franz Erik; Vito, F.; Yang, G.; Basu-Zych, A. R.; Comastri, A.
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    The deepest X-ray view of high-redshift galaxies : constraints on low-rate black hole accretion
    (2016) Vito, F.; Gilli, R.; Vignali, C.; Brandt, W. N.; Comastri, A.; Yang, G.; Lehmer, B. D.; Luo, B.; Basu-Zych, A.; Bauer, Franz Erik
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    The XMM-SERVS survey: new XMM-Newton point-source catalogue for the XMM-LSS field
    (2018) Chen, C-T J.; Brandt, W. N.; Luo, B.; Ranalli, P.; Yang, G.; Alexander, D. M.; Bauer, Franz Erik; Kelson, D. D.; Lacy, M.; Nyland, K.; Tozzi, P.; Vito, F.; Cirasuolo, M.; Gilli, R.; Jarvis, M. J.; Lehmer, B. D.; Paolillo, M.; Schneider, D. P.|