Engineering topics

Jingwen, Wu

Publications and source records attributed to Jingwen, Wu.

6 records

DOE OSTI2013

A NEW POPULATION OF HIGH-z, DUSTY Ly{alpha} EMITTERS AND BLOBS DISCOVERED BY WISE: FEEDBACK CAUGHT IN THE ACT?

By combining data from the NASA Wide-field Infrared Survey Explorer (WISE) mission with optical spectroscopy from the W. M. Keck telescope, we discover a mid-IR color criterion that yields a 78% success rate in identifying rare, typically radio-quiet, 1.6 {approx}< z {approx}< 4.6 dusty Ly{alpha} emitters (LAEs). Of these, at least 37% have emission extended on scales of 30-100 kpc and are considered Ly{alpha} ''blobs'' (LABs). The objects have a surface density of only {approx}0.1 deg{sup -2}, making them rare enough that they have been largely missed in deep, small area surveys. We measured spectroscopic redshifts for 92 of these galaxies, and find that the LAEs (LABs) have a median redshift of 2.3 (2.5). The WISE photometry coupled with data from Herschel (Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA) reveals that these galaxies are in the Hyper Luminous IR galaxy regime (L{sub IR} {approx}> 10{sup 13}-10{sup 14} L{sub Sun }) and have warm colors. They are typically more luminous and warmer than other dusty, z {approx} 2 populations such as submillimeter-selected galaxies and dust-obscured galaxies. These traits are commonly associated with the dust being illuminated by intense active galactic nucleus activity. We hypothesize that the combination of spatially extended Ly{alpha}, large amounts of warm IR-luminous dust, and rarity (implying a short-lived phase) can be explained if the galaxies are undergoing brief, intense ''feedback'' transforming them from an extreme dusty starburst/QSO into a mature galaxy.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2012

SUBMILLIMETER FOLLOW-UP OF WISE-SELECTED HYPERLUMINOUS GALAXIES

We have used the Caltech Submillimeter Observatory (CSO) to follow-up a sample of Wide-field Infrared Survey Explorer (WISE) selected, hyperluminous galaxies, the so-called W1W2-dropout galaxies. This is a rare ({approx}1000 all-sky) population of galaxies at high redshift (peaks at z = 2-3), which are faint or undetected by WISE at 3.4 and 4.6 {mu}m, yet are clearly detected at 12 and 22 {mu}m. The optical spectra of most of these galaxies show significant active galactic nucleus activity. We observed 14 high-redshift (z > 1.7) W1W2-dropout galaxies with SHARC-II at 350-850 {mu}m, with nine detections, and observed 18 with Bolocam at 1.1 mm, with five detections. Warm Spitzer follow-up of 25 targets at 3.6 and 4.5 {mu}m, as well as optical spectra of 12 targets, are also presented in the paper. Combining WISE data with observations from warm Spitzer and CSO, we constructed their mid-IR to millimeter spectral energy distributions (SEDs). These SEDs have a consistent shape, showing significantly higher mid-IR to submillimeter ratios than other galaxy templates, suggesting a hotter dust temperature. We estimate their dust temperatures to be 60-120 K using a single-temperature model. Their infrared luminosities are well over 10{sup 13} L{sub Sun }. These SEDs are not well fitted with existing galaxy templates, suggesting they are a new population with very high luminosity and hot dust. They are likely among the most luminous galaxies in the universe. We argue that they are extreme cases of luminous, hot dust-obscured galaxies (DOGs), possibly representing a short evolutionary phase during galaxy merging and evolution. A better understanding of their long-wavelength properties needs ALMA as well as Herschel data.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2011

EVIDENCE FOR INFLOW IN HIGH-MASS STAR-FORMING CLUMPS

We analyze the HCO{sup +} 3-2 and H{sup 13}CO{sup +} 3-2 line profiles of 27 high-mass star-forming regions to identify asymmetries that are suggestive of mass inflow. Three quantitative measures of line asymmetry are used to indicate whether a line profile is blue, red, or neither-the ratio of the temperature of the blue and red peaks, the line skew, and the dimensionless parameter {delta}v. We find nine HCO{sup +} 3-2 line profiles with a significant blue asymmetry and four with significant red asymmetric profiles. Comparing our HCO{sup +} 3-2 results to HCN 3-2 observations from Wu et al., we find that eight of the blue and three of the red have profiles with the same asymmetry in HCN. The eight sources with blue asymmetries in both tracers are considered strong candidates for inflow. Quantitative measures of the asymmetry (e.g., {delta}v) tend to be larger for HCN. This, combined with possible HCO{sup +} abundance enhancements in outflows, suggests that HCN may be a better tracer of inflow. Understanding the behavior of common molecular tracers like HCO{sup +} in clumps of different masses is important for properly analyzing the line profiles seen in a sample of sources representing a broad range of clump masses. Such studies will soon be possible with the large number of sources with possible self-absorption seen in spectroscopic follow-up observations of clumps identified in the Bolocam Galactic Plane Survey.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2011

WISE DISCOVERY OF LOW-METALLICITY BLUE COMPACT DWARF GALAXIES

We report two new low-metallicity blue compact dwarf galaxies (BCDs), WISEP J080103.93+264053.9 (hereafter W0801+26) and WISEP J170233.53+180306.4 (hereafter W1702+18), discovered using the Wide-field Infrared Survey Explorer (WISE). We identified these two BCDs from their extremely red colors at mid-infrared wavelengths and obtained follow-up optical spectroscopy using the Low Resolution Imaging Spectrometer on Keck I. The mid-infrared properties of these two sources are similar to the well-studied, extremely low metallicity galaxy SBS 0335-052E. We determine metallicities of 12 + log (O/H) = 7.75 and 7.63 for W0801+26 and W1702+18, respectively, placing them among a very small group of very metal deficient galaxies (Z {<=} 1/10 Z{sub sun}). Their >300 A H{beta} equivalent widths, similar to SBS 0335-052E, imply the existence of young (<5 Myr) star-forming regions. We measure star formation rates of 2.6 and 10.9 M{sub sun} yr{sup -1} for W0801+26 and W1702+18, respectively. These BCDs, showing recent star formation activity in extremely low metallicity environments, provide new laboratories for studying star formation in extreme conditions and are low-redshift analogs of the first generation of galaxies to form in the universe. Using the all-sky WISE survey, we discuss a new method to identify similar star-forming, low-metallicity BCDs.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2011

THE PHYSICAL PROPERTIES OF HIGH-MASS STAR-FORMING CLUMPS: A SYSTEMATIC COMPARISON OF MOLECULAR TRACERS

We present observations of HCO{sup +} and H{sup 13}CO{sup +}, N{sub 2}H{sup +}, HCS{sup +}, HNC and HN{sup 13}C, SO and {sup 34}SO, CCH, SO{sub 2}, and CH{sub 3}OH-E toward a sample of 27 high-mass clumps coincident with water maser emission. All transitions are observed with or convolved to nearly identical resolution (30''), allowing for inter-comparison of the clump properties derived from the mapped transitions. We find that N{sub 2}H{sup +} emission is spatially differentiated compared with the dust and the other molecules toward a few very luminous cores (10 of 27) and the N{sub 2}H{sup +} integrated intensity does not correlate well with dust continuum flux. We calculate the effective excitation density, n{sub eff}, the density required to excite a 1 K line in T{sub kin} = 20 K gas for each molecular tracer. The intensity of molecular tracers with larger effective excitation densities (n{sub eff} {>=} 10{sup 5} cm{sup -3}) appears to correlate more strongly with the submillimeter dust continuum intensity. The median sizes of the clumps are anti-correlated with the n{sub eff} of the tracers (which span more than three orders of magnitude). Virial mass is not correlated with n{sub eff}, especially where the lines are optically thick as the linewidths may be broadened significantly by non-virial motions. The median mass surface density and median volume density of the clumps are correlated with n{sub eff} indicating the importance of understanding the excitation conditions of the molecular tracer when deriving the average properties of an ensemble of cores.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2010

THE DECREASE OF SPECIFIC ANGULAR MOMENTUM AND THE HOT TOROID FORMATION: THE MASSIVE CLUMP G10.6-0.4

This is the first paper of our series of high-resolution (1'') studies of the massive star-forming region G10.6-0.4. We present the emission line observations of the hot core type tracers (O{sup 13}CS, OCS, SO{sub 2}) with {approx}0.''5 resolution. By comparing the results to the high-resolution NH{sub 3} absorption line observation, we confirm for the first time the rotationally flattened hot toroid in the central <0.1 pc region, which has a rotational axis perpendicular to its geometrical major axis. In addition, we present the observations of NH{sub 3}, {sup 13}CS, and CH{sub 3}CN with {approx}1'' resolution, and follow the dynamics of the molecular accretion flow from the 0.3 pc radius to the inner 0.03 pc radius. With reference to the rotational axis of the hot toroid, we measure the rotational velocity from the molecular emission in the region. The results are consistent with an envelope with a rapid decrease of the specific angular momentum from the outer to the inner region. These new results improve the current understanding of the molecular accretion flow in an ultracompact H II region created by the embedded O-type cluster.

79 ASTRONOMY AND ASTROPHYSICS↗