Xianzhong Zheng - PMO

Xianzhong Zheng
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Xianzhong Zheng
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PMO
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Astrophysics of Galaxies (9)
 
Astrophysics (5)
 
Cosmology and Nongalactic Astrophysics (4)

Publications Authored By Xianzhong Zheng

We present the first results from the ongoing LAGER project (Lyman Alpha Galaxies in the Epoch of Reionization), which is the largest narrowband survey for $z\sim$ 7 galaxies to date. Using a specially built narrowband filter NB964 for the superb large-area Dark-Energy Camera (DECam) on the NOAO/CTIO 4m Blanco telescope, LAGER has collected 34 hours NB964 narrowband imaging data in the 3 deg$^2$ COSMOS field. We have identified 27 Lyman Alpha Emitter (LAE) candidates at $z=$ 6. Read More

We present our deep $Y$-band imaging data of a two square degree field within the F22 region of the VIMOS VLT Deep Survey. The observations were conducted using the WIRCam instrument mounted at the Canada--France--Hawaii Telescope (CFHT). The total on-sky time was 9 hours, distributed uniformly over 18 tiles. Read More

The Ly$\alpha$ escape fraction is a key measure to constrain the neutral state of the intergalactic medium and then to understand how the universe was fully reionized. We combine deep narrowband imaging data from the custom-made filter NB393 and the $H_{2}S$1 filter centered at 2.14 $\mu$m to examine the Ly$\alpha$ emitters and H$\alpha$ emitters at the same redshift $z=2. Read More

It remains challenging to detect the low surface brightness structures of faint high-z galaxies, which is key to understanding the structural evolution of galaxies. The technique of image stacking allows us to measure the averaged light profile beneath the detection limit and probe the extended structure of a group of galaxies. We carry out simulations to examine the recovery of the averaged surface brightness profile through stacking model HST/ACS images of a set of galaxies as functions of Sersic index (n), effective radius (Re) and axis ratio (AR). Read More

The rest-frame UV-optical (i.e., NUV-B) color index is sensitive to the low-level recent star formation and dust extinction, but it is insensitive to the metallicity. Read More

We examine the evolution of dust attenuation curve using a sample of 9504 disk star-forming galaxies (SFGs) selected from the CANDELS and 3D-HST surveys and a new technique relying on the fact that disk SFGs of similar stellar masses at the same cosmic epoch are statistically identical in stellar populations. We attribute the discrepancy in median magnitude between face-on (b/a>0.7) and edge-on (b/a<=0. Read More

Using a sample of ~6,000 local face-on star-forming galaxies (SFGs), we examine the correlations between the NUV-r colors both inside and outside the half-light radius, stellar mass M* and S\'{e}rsic index n in order to understand how the quenching of star formation is linked to galaxy structure. For these less dust-attenuated galaxies, NUV-r is found to be linearly correlated with Dn4000, supporting that NUV-r is a good photometric indicator of stellar age (or specific star formation rate). We find that: (1) At M*<10^{10. Read More

It is unclear whether bulge growth is responsible for the flattening of the star formation main sequence (MS) at the high mass end. To investigate the role of bulges in shaping the MS, we compare the NUV$-r$ color between the central ($rRead More

We perform a quantitative morphological comparison between the hosts of Active Galactic Nuclei (AGN) and quiescent galaxies at intermediate redshifts (z~0.7). The imaging data are taken from the large HST/ACS mosaics of the GEMS and STAGES surveys. Read More

Both observations and simulations show that major tidal interactions or mergers between gas-rich galaxies can lead to intense bursts of starformation. Yet, the average enhancement in star formation rate (SFR) in major mergers and the contribution of such events to the cosmic SFR are not well estimated. Here we use photometric redshifts, stellar masses and UV SFRs from COMBO-17, 24 micron SFRs from Spitzer and morphologies from two deep HST cosmological survey fields (ECDFS/GEMS and A901/STAGES) to study the enhancement in SFR as a function of projected galaxy separation. Read More

Galaxies migrate from the blue cloud to the red sequence when their star formation is quenched. Here, we report on galaxies quenched by environmental effects and not by mergers or strong AGN as often invoked: They form stars at a reduced rate which is optically even less conspicuous, and manifest a transition population of blue spirals evolving into S0 galaxies. These 'optically passive' or 'red spirals' are found in large numbers in the STAGES project (and by Galaxy Zoo) in the infall region of clusters and groups. Read More

We investigate the properties of optically passive spirals and dusty red galaxies in the A901/2 cluster complex at redshift ~0.17 using restframe near-UV-optical SEDs, 24 micron IR data and HST morphologies from the STAGES dataset. The cluster sample is based on COMBO-17 redshifts with an rms precision of sigma_cz~2000 km/sec. Read More

2008Nov
Affiliations: 1Nottingham, 2Oxford, 3Innsbruck, 4HIA, 5Nottingham, 6MPIA, 7UMass, 8UMass, 9McDonald Observatory, 10Portsmouth, 11Waterloo, 12EPFL, 13AIP, 14UBC, 15MPIA, 16UT Austin, 17Innsbruck, 18Nottingham, 19MPIA, 20Calar Alto, 21PMO, 22UBC, 23PMO, 24Cambridge, 25Manchester, 26NCRA, 27ESO-Santiago, 28IoA Cambridge, 29Texas A&M
Category: Astrophysics

We present an overview of the Space Telescope A901/2 Galaxy Evolution Survey (STAGES). STAGES is a multiwavelength project designed to probe physical drivers of galaxy evolution across a wide range of environments and luminosity. A complex multi-cluster system at z~0. Read More

We present a high resolution dark matter reconstruction of the z=0.165 Abell 901/902 supercluster from a weak lensing analysis of the HST STAGES survey. We detect the four main structures of the supercluster at high significance, resolving substructure within and between the clusters. Read More

We present a brief discussion of the evolution of disk galaxy stellar masses, sizes, rotation velocities, and star formation rates over the last eight billion years. Recent observations have failed to detect significant evolution in the stellar mass Tully-Fisher relation, stellar mass-size relation, and the stellar mass function of disk galaxies. Yet, most z<1 star formation is in disks, and this star formation would be expected to drive a rapid growth of the total stellar mass (and therefore mass function) of disks in the last eight billion years. Read More

2004Jan
Affiliations: 1GEPI, Observatoire de Paris-Meudon, France;, 2GEPI, Observatoire de Paris-Meudon, France;, 3GEPI, Observatoire de Paris-Meudon, France;, 4GEPI, Observatoire de Paris-Meudon, France;, 5CEA-Saclay, France;, 6ESO, Gemany
Category: Astrophysics

Determination of the star formation rate can be done using mid-IR photometry or Balmer line luminosity after a proper correction for extinction effects. Both methods show convergent results while those based on UV or on [OII]3727 luminosities underestimate the SFR by factors ranging from 5 to 40 for starbursts and for luminous IR galaxies, respectively. Most of the evolution of the cosmic star formation density is related to the evolution of luminous compact galaxies and to luminous IR galaxies. Read More