43 research outputs found
UV Luminosity Function at z~4, 3, and 2
We use very deep (R_lim=27) UGRI imaging to study the evolution of the faint
end of the UV-selected galaxy luminosity function from z~4 to z~2. We find that
the number of sub-L* galaxies increases from z~4 to z~3 while the number of
bright ones appears to remain constant. We find no evidence for continued
evolution to lower redshift, z~2. If real, this differential evolution of the
luminosity function suggests that differentially comparing key diagnostics of
dust, stellar populations, etc. as a function of z and L may let us isolate the
key mechanisms that drive galaxy evolution at high redshift and we describe
several such studies currently underway.Comment: To appear in proceedings of the conference "Starbursts - from 30
Doradus to Lyman break galaxies" (IoA, Cambridge UK, Sep 2004), Astrophysics
& Space Science Library, eds. de Grijs R., Gonzalez Delgado R.M. (Kluwer:
Dordrecht
Large-Scale Structure at z~2.5
We have made a statistically complete, unbiased survey of C IV systems toward
a region of high QSO density near the South Galactic Pole using 25 lines of
sight spanning . Such a survey makes an excellent probe of
large-scale structure at early epochs. We find evidence for structure on the
proper Mpc scale ( km Mpc) as
determined by the two point C IV - C IV absorber correlation function, and
reject the null hypothesis that C IV systems are distributed randomly on such
scales at the level. The structure likely reflects the
distance between two groups of absorbers subtending and Mpc at and respectively. There is also a marginal trend for the association of
high rest equivalent width C IV absorbers and QSOs at similar redshifts but
along different lines of sight. The total number of C IV systems detected is
consistent with that which would be expected based on a survey using many
widely separated lines of sight. Using the same data, we also find 11 Mg II
absorbers in a complete survey toward 24 lines of sight; there is no evidence
for Mg II - Mg II or Mg II - QSO clustering, though the sample size is likely
still small to detect such structure if it exists.Comment: 56 pages including 32 of figures, in gzip-ed uuencoded postscript
format, 1 long table not included, aastex4 package. Accepted for publication
in ApJ Supplement
Gas filaments of the cosmic web located around active galaxies in a protocluster
Cosmological simulations predict the Universe contains a network of intergalactic gas filaments, within which galaxies form and evolve. However, the faintness of any emission from these filaments has limited tests of this prediction. We report the detection of rest-frame ultraviolet Lyman-alpha radiation from multiple filaments extending more than one megaparsec between galaxies within the SSA 22 proto-cluster at a redshift of 3.1. Intense star formation and supermassive black-hole activity is occurring within the galaxies embedded in these structures, which are the likely sources of the elevated ionizing radiation powering the observed Lyman-alpha emission. Our observations map the gas in filamentary structures of the type thought to fuel the growth of galaxies and black holes in massive proto-clusters
Inflation and the Scale Dependent Spectral Index: Prospects and Strategies
We consider the running of the spectral index as a probe of both inflation
itself, and of the overall evolution of the very early universe. Surveying a
collection of simple single field inflationary models, we confirm that the
magnitude of the running is relatively consistent, unlike the tensor amplitude,
which varies by orders of magnitude. Given this target, we confirm that the
running is potentially detectable by future large scale structure or 21 cm
observations, but that only the most futuristic measurements can distinguish
between these models on the basis of their running. For any specified
inflationary scenario, the combination of the running index and unknown
post-inflationary expansion history induces a theoretical uncertainty in the
predicted value of the spectral index. This effect can easily dominate the
statistical uncertainty with which Planck and its successors are expected to
measure the spectral index. More positively, upcoming cosmological experiments
thus provide an intriguing probe of physics between TeV and GUT scales by
constraining the reheating history associated with any specified inflationary
model, opening a window into the "primordial dark age" that follows the end of
inflation.Comment: 32 pages. v2 and v3 Minor reference updates /clarification
PTF1 J082340.04+081936.5: A hot subdwarf B star with a low-mass white dwarf companion in an 87-minute orbit
We present the discovery of the hot subdwarf B star (sdB) binary PTF1 J082340.04+081936.5. The system has an orbital period of P orb = 87.49668(1) minutes (0.060761584(10) days), making it the second-most compact sdB binary known. The light curve shows ellipsoidal variations. Under the assumption that the sdB primary is synchronized with the orbit, we find a mass of M sdB = 0.45 +0.09 -0.07 M â , a companion white dwarf mass of M WD = 0.46 + 0.12 -0.09 M â , and a mass ratio of q = M WD /M sdB = 1.03 +0.10 -0.08 . The future evolution was calculated using the MESA stellar evolution code. Adopting a canonical sdB mass of M sdB = 0.47 M â , we find that the sdB still burns helium at the time it will fill its Roche lobe if the orbital period was less than 106 minutes at the exit from the last common envelope (CE) phase. For longer CE exit periods, the sdB will have stopped burning helium and turned into a C/O white dwarf at the time of contact. Comparing the spectroscopically derived log g and T eff with our MESA models, we find that an sdB model with a hydrogen envelope mass of 5 Ă 10 -4 M â matches the measurements at a post-CE age of 94 Myr, corresponding to a post-CE orbital period of 109 minutes, which is close to the limit to start accretion while the sdB is still burning helium
ALMA Reveals Strong [C II] Emission in a Galaxy Embedded in a Giant Lyα Blob at z = 3.1
We report the result from observations conducted with the Atacama Large Millimeter/submillimeter Array (ALMA) to detect [C ii] 158 ÎŒm fine structure line emission from galaxies embedded in one of the most spectacular Lyα blobs (LABs) at z = 3.1, SSA22-LAB1. Of three dusty star-forming galaxies previously discovered by ALMA 860 ÎŒm dust continuum survey toward SSA22-LAB1, we detected the [C ii] line from one, LAB1-ALMA3 at z = 3.0993 ± 0.0004. No line emission was detected, associated with the other ALMA continuum sources or from three rest-frame UV/optical selected zspec sime 3.1 galaxies within the field of view. For LAB1-ALMA3, we find relatively bright [C ii] emission compared to the infrared luminosity (L[C ii]/LIR â 0.01) and an extremely high [C ii] 158 ÎŒm and [N ii] 205 ÎŒm emission line ratio (L[C ii]/L[N ii] > 55). The relatively strong [C ii] emission may be caused by abundant photodissociation regions and sub-solar metallicity, or by shock heating. The origin of the unusually strong [C ii] emission could be causally related to the location within the giant LAB, although the relationship between extended Lyα emission and interstellar medium conditions of associated galaxies is yet to be understand
Properties of Ly-alpha and Gamma Ray Burst selected starbursts at high redshifts
Selection of starbursts through either deep narrow band imaging of redshifted
Ly-alpha emitters, or localisation of host galaxies of gamma-ray bursts both
give access to starburst galaxies that are significantly fainter than what is
currently available from selection techniques based on the continuum (such as
Lyman-break selection). We here present results from a survey for Ly-alpha
emitters at z=3, conducted at the European Southern Observatory's Very Large
Telescope. Furthermore, we briefly describe the properties of host galaxies of
gamma-ray bursts at z>2. The majority of both Ly-alpha and gamma-ray burst
selected starbursts are fainter than the flux limit of the Lyman-break galaxy
sample, suggesting that a significant fraction of the integrated star formation
at z~3 is located in galaxies at the faint end of the luminosity function.Comment: invited talk, 6 pages, 3 figures, to appear in ``Starbursts from 30
Doradus to Lyman Break Galaxies'', eds. R. de Grijs, R. M. Gonzalez Delgado,
Astrophysics & Space Science Library Series, Kluwer (in press
SPECTRA OF YOUNG GALAXIES
Invited review, Ringberg conference on "Galaxies in the Young Universe"
(Sept94)Comment: 12 pages, uuencoded compressed Postscript fil
Reconciling the results of the z ~ 2 MOSDEF and KBSS-MOSFIRE Surveys
Large scale structure and cosmolog