W. W. Liu

National Astronomical Observatories

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Explanation of high redshift luminous galaxies from JWST by an early dark energy model

Physical review. D/Physical review. D. (2025)

Jun-Qian Jiang W. W. Liu Hu Zhan Bin Hu

10.1103/physrevd.111.023519

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Photometric monitoring of three BL Lacertae objects in 1993-1998

Astronomy and Astrophysics Supplement Series (1999)

J. M. Bai Gaogang Xie K. H. Li X. Zhang W. W. Liu

The results of optical photometric monitoring of three BL Lac objects over a time interval of about four years are presented. The sources are three classical radio-selected BL Lac objects, BL Lac, OJ 287 and PKS 0735+178. During our observation OJ 287 was in the stage of a large periodic outburst which consisted of at least two peaks. Almost all the observations obtained over consecutive nights detected intranight variations. In 1995 and 1996 BL Lac kept in faint states, with fewer and smaller rapid flares and fluctuations. On the contrary, in late 1997 BL Lac was at the stage of a large outburst, accompanied with much more large amplitude rapid flares and fluctuations. PKS 0735+178 was almost at its faint end from 1994 to early 1998. Over this time interval, the intraday variations and microvariations in PKS 0735+178 were rare and the amplitude was very small, except a rapid darkening of mag on 24 January 1995. Previous work by Webb et al. (1988); Wagner et al. (1996); Pian et al. (1997) also showed the same behaviour of variability as BL Lac and PKS 0735+178 in BL Lac, S5 0716+714, PKS 2155-304, respectively. We propose that the motion of orientation of the relativistic jet in a BL Lac object be responsible for these variability behaviours.

BL Lac object

10.1051/aas:1999227

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Citations (40)

Rapid Optical Variability of Gamma-Ray–loud Blazars

The Astronomical Journal (2001)

B. Z. Dai Gaogang Xie K. H. Li Shaobing Zhou W. W. Liu

We present the optical (B, V, and R) photometry for nine GeV and/or TeV γ-ray blazars, which were observed from 2000 through 2001 with the 1 m telescope at Yunnan Astronomical Observatory. The GeV γ-ray–loud source PKS 1510-089 was very active during our observation period, showing an apparent variation of 2.0 mag within 41 minutes in the R band. This is the most violently rapid variability in our optical monitoring program since 1982. Some physics parameters are calculated for this source, namely, the emission size, Doppler factor δ, the efficiency (η) for conversion of accreted matter into energy, and luminosity. An η = 62.2 was obtained, strongly implying that relativistic beaming is responsible for the rapid variability of the γ-ray–loud source. The influence of variable seeing conditions on the observations was investigated. There is a weak correlation between the observed variability and the local seeing conditions for the object 1ES 2344+51.4.

BL Lac object

10.1086/324450

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Citations (45)

Can early dark energy be probed by the high-redshift galaxy abundance?

Monthly Notices of the Royal Astronomical Society (2024)

W. W. Liu Hu Zhan Yan Gong Xin Wang

ABSTRACT The analysis of the cosmic microwave background data acquired by the Atacama Cosmology Telescope and the large-scale ($\ell \lesssim 1300$) Planck Telescope show a preference for the early dark energy (EDE) theory, which was set to alleviate the Hubble tension of the $\Lambda$ cold dark matter ($\Lambda$CDM) model by decreasing the sound horizon $r_{s}$, and gives $H_{0} \approx 72$ km s$^{-1}$ Mpc$^{-1}$. However, the EDE model is commonly questioned for exacerbating the $\sigma _8$ tension on top of the $\Lambda$CDM model, and its lack of preference from the late-time matter power spectrum observations, e.g. Baryon Oscillation Spectroscopic Survey. In light of the current obscurities, we inspect if the high redshift galaxy abundance, i.e. stellar mass function/density and luminosity function, can independently probe the EDE model. Our result shows that, compared to $\Lambda$CDM, the EDE model prediction at $z\gt 10$ displays better consistency with the unexpectedly high results observed by the JWST. At lower redshift, the EDE model only fits the most luminous/massive end, with the majority of the data presenting better consistency with $\Lambda$CDM, implying that adding an extra luminosity/mass-sensitive suppression mechanism of the galaxy formation is required for EDE to explain all data around $z\sim 7-10$.

Baryon Acoustic Oscillations

Cold dark matter

10.1093/mnras/stae1871

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Citations (1)

The intraday variability in the radio-selected and X-ray-selected BL Lacertae objects

Astronomy and Astrophysics Supplement Series (1998)

J. M. Bai Gaogang Xie K. H. Li X. Zhang W. W. Liu

Seven BL Lac objects have been photometrically observed in an effort to study the difference of optical intraday variability between the radio-selected BL Lac objects (RBLs) and X-ray-selected BL Lac objects (XBLs). The objects we observed are selected arbitrarily. They are four RBLs, PKS 0735+178, PKS 0754+101, OJ 287 and BL Lac, and three XBLs, H 0323+022, H 0548-322 and H 2154-304. During the observation all of them exhibited microvariation, and H 0323+022 and H 0548-322 sometimes showed brightness oscillation. PKS 0735+178 and BL Lac were in their faint states and not very active. It seems that RBLs do not show microvariability more frequently than XBLs.

BL Lac object

10.1051/aas:1998360

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Citations (62)