12 research outputs found
A New Population of High-z, Dusty Lyα 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 ≾ z ≾ 4.6 dusty Lyα emitters (LAEs). Of these, at least 37% have emission extended on scales of 30-100 kpc and are considered Lyα "blobs" (LABs). The objects have a surface density of only ~0.1 deg^(–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 IR ≳ 10^(13)-10^(14) L_☉) and have warm colors. They are typically more luminous and warmer than other dusty, z ~ 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 Lyα, 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
Understanding the nature of the optically faint radio sources and their connection to the submillimeter population
We present a sample of 43 submillimeter sources detected (at >3 sigma), drawn
from our program to follow-up optically faint radio sources with SCUBA. These
sources already have associated radio and in many cases optical
identifications, and many are also detected at 450 microns. We compare these
with 12 submillimeter sources drawn from the literature, which were discovered
in blank field mapping campaigns, but also have radio detections. We then use
this total sample (55 sources) to study and model the evolution of dusty
galaxies. A correlation is observed in the sub-mm/radio color-magnitude
diagram, which can be modeled by strong luminosity evolution. The selection
effects of the radio/optical pre-selection technique are determined from the
models, and a corrected redshift distribution is constrained using a range of
model assumptions. The temperature/redshift effects on the 450 microns detected
subset of our sample are studied in relation to the models, and prospects for
improved measurements in the shorter sub-mm wavelength windows (450 microns and
350 microns) are explored.Comment: to appear in ApJ, 19 pages, 9 figure
First Constraints on Source Counts at 350 Microns
We have imaged a 6 arcminute region in the Bo\"otes Deep Field
using the 350 m-optimised second generation Submillimeter High Angular
Resolution Camera (SHARC II), achieving a peak 1 sensitivity of 5
mJy. We detect three sources above 3, and determine a spurious source
detection rate of 1.09 in our maps. In the absence of detections, we
rely on deep 24 m and 20 cm imaging to deduce which sources are most
likely to be genuine, giving two real sources. From this we derive an integral
source count of 0.84 sources arcmin at mJy,
which is consistent with 350 m source count models that have an
IR-luminous galaxy population evolving with redshift. We use these constraints
to consider the future for ground-based short-submillimetre surveys.Comment: accepted for publication in The Astrophysical Journa
A New Population of High Redshift, Dusty Lyman-Alpha Emitters and Blobs Discovered by WISE
We report a new technique to select 1.6<z<4.6 dusty Lyman-alpha emitters
(LAEs), over a third of which are `blobs' (LABs) with emission extended on
scales of 30-100kpc. Combining data from the NASA Wide-field Infrared Survey
Explorer (WISE) mission with optical spectroscopy from the W.M. Keck telescope,
we present a color criteria that yields a 78% success rate in identifying rare,
dusty LAEs of which at least 37% are LABs. The objects have a surface density
of only ~0.1 per square degree, making them rare enough that they have been
largely missed in narrow surveys. We measured spectroscopic redshifts for 92 of
these WISE-selected, typically radio-quiet galaxies and find that the LAEs
(LABs) have a median redshift of 2.3 (2.5). The WISE photometry coupled with
data from Herschel reveals that these galaxies have extreme far-infrared
luminosities (L_IR>10^{13-14}L_sun) and warm colors, typically larger than
submillimeter-selected galaxies (SMGs) and dust-obscured galaxies (DOGs). These
traits are commonly associated with the dust being energized by intense AGN
activity. We hypothesize that the combination of spatially extended
Lyman-alpha, large amounts of warm IR-luminous dust, and rarity (implying a
short-lived phase) can be explained if the galaxies are undergoing strong
`feedback' transforming them from an extreme dusty starburst to a QSO.Comment: Submitted to ApJ Letters, 6 pages, 4 figures. Comments welcom
A New Population of High-z, Dusty Lyman-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. 10(exp 13)-10(exp 14) Solar L) 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
Chemical constituents in the air and snow at Dye 3, Greenland—I. Seasonal variations
International audienc
Chemical constituents in the air and snow at Dye 3, Greenland—II. Analysis of episodes in April 1989
Detailed examination of a two-week period in April 1989 during the Dye 3 Gas and Aerosol Sampling Program shows that episodes of relatively high concentration of certain chemical constituents occur at this time of year. Airborne concentrations of crustal metals such as Al and Ca can exceed 100 ng m−3, while concentrations of SO42− can exceed 1000 ng m−3. Elevated concentrations of MSA, 7Be and 210Pb are also noted. Consideration of synoptic maps and backward air mass trajectories suggests that the episodes are due to transport from a variety of source regions, including Eurasia (transport over the Pole), North America and western Europe. In addition to elevated airborne concentrations, levels of these constituents in surface snow are high during April. However, it is difficult to develop quantitative relationships between concentrations in air and in snow due to the difficulty in measuring airborne concentrations at cloud-level; variations in scavenging by clouds may also be significant. It is concluded that the springtime maxima in airborne concentrations resulting from long-range transport from a variety of source regions are responsible for strong identifiable signals in ice cores and snowpits from this region