arXiv subjects

Huiyang Mao

Publications and source records attributed to Huiyang Mao.

5 recordsLinked to original sources

arXiv2026

A quiescent galaxy in a gas-rich cosmic web node at z~3

Recent JWST observations have unveiled a large number of quiescent galaxies at $z\gtrsim3$, bringing potential challenges to current galaxy formation models. Since star formation is expected to be fed by external gas accretion, the knowledge about the circumgalactic media (CGM) of these galaxies is essential to understanding how they quench. In this work, we present the discovery of a massive and passive galaxy ($M_\star\simeq10^{11}\,M_\odot$) within the MQN01 structure at z~3.25, containing one of the largest overdensities of galaxies and active galactic nuclei (AGN) found so far at $z\gtrsim3$. The passive galaxy has a star-formation rate of $4^{+6}_{-2}~M_\odot$/yr, placing it more than 1 dex below the star-forming main sequence, and has no detectable molecular gas ($M_\mathrm{H2}<7\times10^{9}\,M_\odot$). Surprisingly, it is located at the center of a large cool gas reservoir, as traced by bright Ly$α$ and H$α$ emission. By taking advantage of deep multi-wavelength information unique to this field, including deep Chandra X-ray data, we argue that the inefficient gas accretion from the CGM onto this galaxy over the last few hundreds of Myr, as suggested by the observations, could be caused by an AGN jet of a nearby star-forming galaxy located at a projected distance of 48 kpc. In particular, we argue that the jet feedback may have maintained a high level of CGM turbulence around the passive galaxy and thus caused a reduced gas accretion over the required time-scales. In addition, the elevated ionizing field provided by the AGN overdensity, including the nearby AGN, can illuminate the passive galaxy's cool CGM and make it visible through fluorescent emission. Our study demonstrates that the star formation rates of high-redshift galaxies could be substantially reduced and maintained at a low level even within gas-rich and overdense environments in particular situations.

astro-ph.GA↗

arXiv2025

Probing the \ion{He}{2} re-Ionization ERa via Absorbing \ion{C}{4} Historical Yield (HIERACHY) IV: A complex redshifted absorption system intrinsic to quasar

High-resolution spectra provide a powerful tool in studying the associated absorption lines (AALs) in quasars. We present a case study of the quasar J014741-030247 at $z \sim$ 4.75, which hosts complex intrinsic absorption lines revealed by the high-resolution Magellan/MIKE spectrum obtained from the HIERACHY program. We focus on one of the strongest absorption systems ($z$ $\sim$ 4.7804) and determine the column densities of multiple ionization species. We find that the Apparent Optical Depth method may significantly underestimate the column densities of high ions. Decomposing the absorption into multiple components yields a better fit and reveals clear evidence of partial coverage. The variation in covering fractions among different ions suggests that high ions are distributed more extensively in this system. We estimate electron densities of different components ($630 - 4070 \ \mathrm{cm}^{-3}$), these are based on the column densities of \ion{Si}{2}* and \ion{C}{2}*. By combining these with the hydrogen number density and ionization parameter derived from photoionization modeling, we infer that the different components are located at distances of 2.3 to 9.5 kpc from the quasar. The derived $N_{\mathrm H} / n_{\mathrm e}$ and the partial coverage observed in low ions all require cloud sizes smaller than 1 pc, even down to 0.01 pc. Finally, the low kinetic luminosity of the gas ($< 0.5\% L_\mathrm{bol}$) indicates that it is insufficient to drive significant AGN feedback and may only suppress star formation via `multistage' mechanism.

astro-ph.GA↗

arXiv2025

Probing the He II reionization ERa via Absorbing C IV Historical Yield (HIERACHY) III: The C IV absorber catalog and initial results on cosmic abundance evolution at $z\approx 3-5$

As part of the HIERACHY program, we collect the high-SN and high-spectral resolution optical spectra of 25 quasars at $z\approx4-5$ to constrain the C IV evolution at $z\approx 3-5$. In this paper, we report a catalog of 626 (1263) C IV absorption systems (components) at $z\approx3-5$ with a 50% completeness column density of log$(N_{\rm CIV}/\rm cm^{-2}) \approx 12.3$. The HIERACHY/MIKE C IV sample is one of the best C IV absorber samples optimized to study the IGM during the He II reionization epoch. Using 557 (1090) intervening absorption systems (components), we found the column density distribution function of C IV absorption systems with log$(N_{\rm CIV}/\rm cm^{-2})\gtrsim 12.3$ has a broken power-law shape, with the turn-over column density log$(N_{\rm crit}/\rm cm^{-2}) = 13.35^{+0.20}_{-0.19}$, which is close to or smaller than the detection limit of most literature samples. We also found that both comoving path length number density $dn/dX$ and cosmic abundance $Ω$ for C IV absorption systems with log$(N_{\rm CIV}/\rm cm^{-2})> 13.2$ show an increase (at the 2.2$σ$ and 1.4$σ$ levels, respectively) from redshift $z\approx5$ to 3, while absorption systems with log$(N_{\rm CIV}/\rm cm^{-2})= 12.3-13.2$ exhibit a constant $dn/dX$ and $Ω_{\rm CIV}$.

astro-ph.GA↗

arXiv2024

Probing the He II re-Ionization ERa via Absorbing C IV Historical Yield (HIERACHY) II: Project Design, Current Status, and Examples of Initial Data Products

The He II reionization epoch is expected to take place at $z\sim3-5$. In this stage, the helium and metals in the inter-galactic medium (IGM) are further ionized with additional contributions from harder non-stellar sources, and some large-scale gravitationally bound systems approach virialization. The "Probing the He II re-Ionization ERa via Absorbing C IV Historical Yield (HIERACHY)" program utilizes high- and medium-resolution spectra of bright background quasars at $z\approx3.9-5.2$ to investigate Ly$α$, C IV, and other metal absorption lines during this epoch. Additionally, we employ narrow-band imaging to search for Ly$α$ emitters associated with C IV absorbers, alongside multi-wavelength observations to identify and study particularly intriguing cases. In this paper, we present the design of the HIERACHY program, its current status, major scientific goals, and examples of initial data products from completed Magellan/MIKE, MagE spectroscopy, and MDM imaging observations. We also provide a brief outlook on future multi-wavelength observations that may significantly impact the related science.

astro-ph.GA↗

arXiv2024

Optical observations of the Galactic SNR HB9 and H II region G159.2+3.3

Context. We present multi-wavelength observations of the Galactic SNR HB9 and the H II region G159.2+3.3 apparently projected nearby, in order to study their properties and potential physical connections. Results. HB9 is bright in $γ$-rays, but the $γ$-ray morphology is centrally filled and most of it is not clearly associated with the surrounding molecular clouds. There is a weak apparent connection of HB9 to the IR bright enclosing shell of G159.2+3.3 in $γ$-ray. The diffuse Balmer line has almost identical morphology as the radio emission in G159.2+3.3, indicating they two are thermal in origin. Using medium-band high-resolution optical spectra from selected regions of the southeast (SE) shell of HB9 and G159.2+3.3, we found the radial velocity dispersion of HB9 along the slit is significantly higher than the FWHM of the lines. In contrast, these two values are both smaller and comparable to each other in G159.2+3.3. This indicates that the gas in HB9 may have additional global motion triggered by the SNR shock. The [N II] $λ$6583A/H$α$ line ratio of both objects can be interpreted with photo-ionisation by hot stars or low velocity shocks, except for the post-shock region in the SE shell of HB9, where the elevated [N II]/H$α$ line ratio suggests contribution from shock ionisation. The measured electron density from the [S II] 6716/6730 line ratio is significantly lower in the brighter G159.2+3.3 compared to the SE shell of HB9. Conclusions. Our density estimate suggests that G159.2+3.3, although appearing brighter and more compact, is likely located at a much larger distance than HB9, so the two objects have no physical connections, unless the shock compressed gas in HB9 has a significantly lower filling factor.

astro-ph.HE↗