25 research outputs found
Lyα view around a z = 2.84 hyperluminous QSO at a node of the cosmic web
We report on the results of deep and wide-field (1.1 deg²) narrow-band observations with Subaru/Hyper Suprime-Cam (HSC) of a field around a hyperluminous QSO (HLQSO), HS1549+1549+1919, residing in a protocluster at z = 2.84, to map the large-scale structure of Lyα emitters (LAEs). One HSC pointing enables us to detect 3490 LAEs and 76 extended Lyα blobs (LABs), probing diverse environments from voids to protoclusters. The HLQSO is found to be near the center of the protocluster, which corresponds to the intersection of ∼100 comoving Mpc-scale structures of LAEs. LABs are basically distributed along the large-scale structure, with larger ones particularly clustering around the HLQSO, confirming a previously noted tendency of LABs to prefer denser environments. Moreover, the shapes of LABs near the HLQSO appear to be aligned with the large-scale structure. Finally, a deep Lyα image reveals a diffuse Lyα nebula along a filamentary structure with no luminous UV/sub-mm counterpart. We suggest that the diffuse nebula is due to a cold filament with high clumping factor illuminated by the QSO, with the required high clumpiness provided by unresolved residing halos of mass ≤10⁹⁻¹⁰ M_⊙
A Keck/DEIMOS Spectroscopy of Lyman Alpha Blobs at Redshift z=3.1
We present the results of an intermediate resolution (~2 angstrom)
spectroscopy of a sample of 37 candidate Lyman alpha blobs and emitters at
redshift z=3.1 using the DEIMOS spectrograph on the 10 m Keck telescope. The
emission lines are detected for all the 37 objects and have variety in their
line profiles. The Lyman alpha velocity widths (FWHM) of the 28 objects with
higher quality spectra, measured by fitting a single Gaussian profile, are in
the range of 150 - 1700 km/s and correlate with the Lyman alpha spatial
extents. All the 12 Lyman alpha blobs (>16 arcsec^2) have large velocity widths
of > 500 km/s. While there are several possible physical interpretations of the
Lyman alpha velocity widths (motion of gravitationally-bound gas clouds,
inflows, merging of clumps, or outflows from superwinds), the large velocity
widths of the Lyman alpha blobs suggest that they are the sites of massive
galaxy formation. If we assume gravitationally-bound gas clouds, the dynamical
masses of the Lyman alpha blobs are estimated to be ~10^12 - 10^13 Msun. Even
for the case of outflows, the outflow velocities are likely to be the same
order of the rotation velocities as inferred from the observational evidence
for local starburst galaxies.Comment: Accepted for publication in ApJ
Large-scale Filamentary Structure around the Protocluster at Redshift z=3.1
We report the discovery of a large-scale coherent filamentary structure of
Lyman alpha emitters in a redshift space at z=3.1. We carried out spectroscopic
observations to map the three dimensional structure of the belt-like feature of
the Lyman alpha emitters discovered by our previous narrow-band imaging
observations centered on the protocluster at z=3.1. The feature was found to
consist of at least three physical filaments connecting with each other. The
result is in qualitative agreement with the prediction of the 'biased'
galaxy-formation theories that galaxies preferentially formed in large-scale
filamentary or sheet-like mass overdensities in the early Universe. We also
found that the two known giant Lyman alpha emission-line nebulae showing high
star-formation activities are located near the intersection of these filaments,
which presumably evolves into a massive cluster of galaxies in the local
Universe. This may suggest that massive galaxy formation occurs at the
characteristic place in the surrounding large-scale structure at high redshift.Comment: 11 pages, 3 figures, accepted for publication in ApJ Letter
Assembly of Massive Galaxies in a High-z Protocluster
We present the results of wide-field deep JHK imaging of the SSA22 field
using MOIRCS instrument equipped with Subaru telescope. The observed field is
112 arcmin^2 in area, which covers the z=3.1 protocluster characterized by the
overdensities of Ly Alpha emitters (LAEs) and Ly Alpha Blobs (LABs). The 5
sigma limiting magnitude is K_{AB} = 24.3. We extract the potential
protocluster members from the K-selected sample by using the multi-band
photometric-redshift selection as well as the simple color cut for distant red
galaxies (DRGs; J-K_{AB}>1.4). The surface number density of DRGs in our
observed fields shows clear excess compared with those in the blank fields, and
the location of the densest area whose projected overdensity is twice the
average coincides with the large-scale density peak of LAEs. We also found that
K-band counterparts with z_{phot} = 3.1 are detected for 75% (15/20) of the
LABs within their Ly Alpha halo, and the 40 % (8/20) of LABs have multiple
components, which gives a direct evidence of the hierarchical multiple merging
in galaxy formation. The stellar mass ofLABs correlates with their luminosity,
isophotal area, and the Ly Alpha velocity widths, implying that the physical
scale and the dynamical motion of Ly Alpha emission are closely related to
their previous star-formation activities. Highly dust-obscured galaxies such as
hyper extremely red objects (HEROs; J-K_{AB}>2.1) and plausible K-band
counterparts of submillimeter sources are also populated in the high density
region.Comment: 21pages, accepted for publication in Astrophysical Journa
The Luminosity Function of Lyman Alpha Emitters at Redshift z~5.7
We report results of a deep wide-field narrowband survey for redshift z~5.7
Ly alpha emitters carried out with SuprimeCam on Subaru 8.3-m telescope. Deep
narrowband imaging of the SSA22 field through a 120 A bandpass filter centered
at 8150 A was combined with deep multicolor RIz' SuprimeCam broadband imaging,
and BVRZ imaging taken with CFHT's CFH12K camera to select high-redshift galaxy
candidates. Spectroscopic observations were made using the new wide-field
multi-object DEIMOS spectrograph on Keck for 22 of the 26 candidate objects.
Eighteen objects were identified as z~5.7 Lyman alpha emitters, and a further
nineteenth candidate was identified based on an LRIS spectrum. At the 3.3 A
resolution of the DEIMOS spectra the asymmetric profile for Ly alpha emission
with its steep blue fall-off can be clearly seen. We use this to describe the
distribution of equivalent widths and the continuum color break properties for
z~5.7 Ly alpha galaxies compared with foreground objects. The large majority
(>75%) of Ly alpha lines have rest frame equivalent widths less than 240 A and
can be understood in terms of young star forming galaxies with a Salpeter
initial mass function for the stars. With narrowband selection criteria of I-N
> 0.7 and N<25.05 (AB mags) we find a surface density of Ly alpha emitters of
0.03 per square arcminute per (deltaz=0.1) to a limiting flux just under 2e-17
erg/cm2/s. The luminosity function of the Ly alpha emitters is similar to that
at lower redshifts to the lowest measurable luminosity of 1e43 ergs/s as is the
universal star formation rate based on their continuum properties. We note that
the objects are highly structured in both spatial and spectral properties on
the angular scale of the fields (~60 Mpc), and that multiple fields will have
to be averaged to accurately measure their ensemble properties.Comment: 12 pages, 20 figures, emulateapj, to appear in the Astronomical
Journal (February 2004), version with higher quality figures available at
http://www.ifa.hawaii.edu/publications/preprints/Hu_03-95.pdf Fixed problem
with cited papers appearing as numbered hypertex links instead of text (only
affected astro-ph pdf file
Constraining Dust and Molecular Gas Properties in Lyα Blobs at z ~ 3
In order to constrain the bolometric luminosities, dust properties, and molecular gas content of giant Lyα nebulae, the so-called Lyα blobs, we have carried out a study of dust continuum and CO line emission in two well-studied representatives of this population at z ~ 3: an Lyα blob discovered by its strong Spitzer Multiband Infrared Photometer 24 μm detection (LABd05) and the Steidel blob 1 (SSA22-LAB01). We find that the spectral energy distribution of LABd05 is well described by an active-galactic-nucleus-starburst composite template with L_(FIR) = (4.0 ± 0.5) × 10^(12) L_☉, comparable to high-z submillimeter galaxies and ultraluminous infrared galaxies. New Large APEX Bolometer Camera 870 μm measurements rule out the reported Submillimeter Common-User Bolometer Array detection of the SSA22-LAB01 (S_(850 μm) = 16.8 mJy) at the >4σ level. Consistent with this, ultradeep Plateau de Bure Interferometer observations with ~2'' spatial resolution also fail to detect any 1.2 mm continuum source down to ≈0.45 mJy beam^(–1) (3σ). Combined with the existing (sub)millimeter observations in the literature, we conclude that the FIR luminosity of SSA22-LAB01 remains uncertain. No CO line is detected in either case down to integrated flux limits of S_νΔV ≾ 0.25-1.0 Jy km s^(–1), indicating a modest molecular gas reservoir, M(H_2) < (1-3) × 10^(10) M_☉. The non-detections exclude, with high significance (12σ), the previous tentative detection of a CO J = 4-3 line in the SSA22-LAB01. The increased sensitivity afforded by the Atacama Large Millimeter/submillimeter Array will be critical in studying molecular gas and dust in these interesting systems
The Subaru Deep Field Project: Lyman Emitters at Redshift of 6.6
We present new results of a deep optical imaging survey using a narrowband
filter () centered at 9196 \AA ~ together with , ,
, , and broadband filters in the sky area of the Subaru
Deep Field which has been promoted as one of legacy programs of the 8.2m Subaru
Telescope. We obtained a photometric sample of 58 Ly emitter candidates
at 6.5 -- 6.6 among strong -excess () objects together with a color criterion of . We then obtained optical spectra of 20 objects in our -excess
sample and identified at least nine Ly emitters at -- 6.6
including the two emitters reported by Kodaira et al. (2003). Since our
Ly emitter candidates are free from strong amplification of
gravitational lensing, we are able to discuss their observational properties
from a statistical point of view. Based on these new results, we obtain a lower
limit of the star formation rate density of yr Mpc at , being
consistent with our previous estimate. We discuss the nature of star-formation
activity in galaxies beyond .Comment: 49 pages, 16 figures, PASJ, Vol. 57, No. 1, in pres