37 research outputs found
The SED of the nearby HI-massive LIRG HIZOA J0836-43: from the NIR to the radio domain
HIZOA J0836-43is one of the most HI-massive galaxies in the local (z<0.1)
Universe. Not only are such galaxies extremely rare, but this "coelacanth"
galaxy exhibits characteristics -- in particular its active, inside-out stellar
disk-building -- that appear more typical of past (z ~ 1) star formation, when
large gas fractions were more common. Unlike most local giant HI galaxies, it
is actively star forming. Moreover, the strong infrared emission is not induced
by a merger event or AGN, as is commonly found in other local LIRGs. The galaxy
is suggestive of a scaled-up version of local spiral galaxies; its extended
star formation activity likely being fueled by its large gas reservoir and, as
such, can aid our understanding of star formation in systems expected to
dominate at higher redshifts. The multi-wavelength imaging and spectroscopic
observations that have led to these deductions will be presented. These include
NIR (J H K) and MIR (Spitzer; 3-24micron) imaging and photometry, MIR
spectroscopy, ATCA HI-interferometry and Mopra CO line emission observations.
But no optical data, as the galaxy is heavily obscured due to its location in
Vela behind the Milky Way.Comment: 5 pages, 3 figures, to appear in the proceedings of IAU Symposium
284, "The Spectral Energy Distribution of Galaxies" (SED2011), 5-9 September
2011, Preston, UK, editors R.J. Tuffs & C.C.Popesc
An Overview of Uncovered and Suspected Large-Scale Structures behind the Milky Way
Various dynamically important extragalactic large-scale structures in the
local Universe lie behind the Milky Way. Most of these structures (predicted
and unexpected) have only recently been made ``visible'' through dedicated deep
surveys at various wavelengths. The wide range of observational searches
(optical, near infrared, far infrared, radio and X-ray) for galaxies in the
Zone of Avoidance (ZOA) will be reviewed and the uncovered and suspected
large-scale structures summarised. Particular emphasis is given to the Great
Attractor region where the existence of yet another cluster is suspected (Woudt
1998). Predictions from reconstructions of the density field in the ZOA are
discussed and compared with observational evidence. Although no major
structures are predicted out to about v < 10000 km/s for which no observational
evidence exists, the comparison between reconstructed density fields and the
observed galaxy distribution remain important as they allow derivations of the
density and biasing parameters.Comment: To appear in PASA 16. Proceedings of workshop "HI in the Local
Universe, II", held in Melbourne, Sept. 1998. 9 pages, LaTeX2e, 1
encapsulated PS figur
The HI mass function in the Parkes HI Zone of Avoidance survey
An HI mass function (HIMF) was derived for 751 galaxies selected from the
deep Parkes HI survey across the Zone of Avoidance (HIZOA). HIZOA contains both
the Great Attractor Wall and the Local Void, two of the most extreme
environments in the local Universe, making the sample eminently suitable to
explore the overall HIMF as well as its dependence on local environment. To
avoid any selection bias because of the different distances of these
large-scale structures, we first used the two-dimensional stepwise
maximum-likelihood method for the definition of an average HIMF. The resulting
parameters of a Schechter-type HIMF for the whole sample are , , and Mpc. We then used the -th
nearest-neighbour method to subdivide the sample into four environments of
decreasing local density and derived the Schechter parameters for each
subsample. A strong trend is observed, for the slope of the low-mass
end of the HIMF. The slope changes from being nearly flat, i.e. for galaxies residing in the densest bin, to the steep value of
in the lowest density bin. The characteristic mass,
however, does not show a clear trend between the highest and lowest density
bins. We find similar trends in the low-mass slope when we compare the results
for a region dominated by the Great Attractor, and the Local Void, which are
found to be over-, respectively underdense by 1.35 and 0.59 compared to the
whole sample.Comment: 10 pages, 13 figures, 4 tables, accepted for publication in MNRA
Mapping the Hidden Universe: The Galaxy Distribution in the Zone of Avoidance
Due to the foreground extinction of the Milky Way, galaxies become
increasingly faint as they approach the Galactic Equator creating a ``zone of
avoidance'' (ZOA) in the distribution of optically visible galaxies of about
25%. A ``whole-sky'' map of galaxies is essential, however, for understanding
the dynamics in our local Universe, in particular the peculiar velocity of the
Local Group with respect to the Cosmic Microwave Background and velocity flow
fields such as in the Great Attractor (GA) region. The current status of deep
optical galaxy searches behind the Milky Way and their completeness as a
function of foreground extinction will be reviewed. It has been shown that
these surveys - which in the mean time cover the whole ZOA (Fig. 2) - result in
a considerable reduction of the ZOA from extinction levels of A_B = 1.0 mag
(Fig. 1) to A_B = 3.0 mag (Fig. 2). In the remaining, optically opaque ZOA,
systematic HI surveys are powerful in uncovering galaxies, as is demonstrated
for the GA region with data from the full sensitivity Parkes Multibeam HI
survey (300 < l < 332 deg, |b| < 5.5 deg, Fig. 4).Comment: Accepted for publication in PASA (Volume 17, 1, to appear April
2000); LaTex, 4 encapsulated (reduced) ps-figures, requires psfig.
Full-resolution color figures 1, 3, and 4 are available upon request at
e-mail: [email protected] or at http://www.atnf.csiro.au/pasa/17_1
NIR Tully-Fisher in the Zone of Avoidance. -- III. Deep NIR catalogue of the HIZOA galaxies
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. ©: 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.We present a deep near-infrared (NIR) photometric catalogue of sources from the Parkes HI Zone of Avoidance (HIZOA) survey, which forms the basis for an investigation of the matter distribution in the Zone of Avoidance. Observations were conducted between 2006 and 2013 using the Infrared Survey Facility (IRSF), a 1.4-m telescope situated at the South African Astronomical Observatory site in Sutherland. The images cover all 1108 HIZOA detections and yield 915 galaxies. An additional 105 bright 2MASS galaxies in the southern ZOA were imaged with the IRSF, resulting in 129 galaxies. The average -band seeing and sky background for the survey are 1.38 arcsec and 20.1 mag, respectively. The detection rate as a function of stellar density and dust extinction is found to depend mainly on the HI mass of the HI detected galaxies, which in principal correlates with the NIR brightness of the spiral galaxies. The measured isophotal magnitudes are of sufficient accuracy (errors 0.02 mag) to be used in a Tully-Fisher analysis. In the final NIR catalogue, 285 galaxies have both IRSF and 2MASS photometry (180 HIZOA plus 105 bright 2MASX galaxies). The -band isophotal magnitudes presented in this paper agree, within the uncertainties, with those reported in the 2MASX catalogue. Another 30 galaxies, from the HIZOA northern extension, are also covered by UKIDSS Galactic Plane Survey (GPS) images, which are one magnitude deeper than our IRSF images. A modified version of our photometry pipeline was used to derive the photometric parameters of these UKIDSS galaxies. Good agreement was found between the respective -band isophotal magnitudes. These comparisons confirm the robustness of the isophotal parameters and demonstrate that the IRSF images do not suffer from foreground contamination, after star removal, nor under-estimate the isophotal fluxes of ZoA galaxies.Peer reviewe
NIR Tully-Fisher in the Zone of Avoidance. - II. 21 cm HI-line spectra of southern ZOA galaxies
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © : 2016 [Khaled Said, Renee C. Kraan-Korteweg, Lister Staveley-Smith, Wendy L. Williams, T. H . Jarrett, Christopher M. Springob, 'NIR Tully–Fisher in the Zone of Avoidance – II. 21 cm H i-line spectra of southern ZOA galaxies', MNRAS (2016) 457(3): 2366-2377]. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. The version of record is available on line via doi: https:doi.org/10.1093/mnras/stw105High-accuracy H I profiles and linewidths are presented for inclined ((b/a) o 5) for use in TF distance estimation. The average value of the signal-to-noise ratio of the sample is 14.7. We present the H I parameters for these galaxies. The sample will allow a more accurate determination of the flow field in the southern ZOA which bisects dynamically important large-scale structures such as Puppis, the Great Attractor, and the Local Void.Peer reviewedFinal Published versio
A nearby isolated dwarf: star formation and structure of ESO 006-001
Observations with the Hubble Space Telescope unexpectedly revealed that the
dwarf galaxy ESO 006-001 is a near neighbor to the Local Group at a distance of
2.70 +- 0.11 Mpc. The stellar population in the galaxy is well resolved into
individual stars to a limit of M I ~ -0.5 mag. The dominant population is older
than 12 Gyr yet displays a significant range in metallicity of -2 < [Fe/H] <
-1, as evidenced by a Red Giant Branch with substantial width. Superimposed on
the dominant population are stars on the Main Sequence with ages less than 100
Myr and Helium burning Blue Loop stars with ages of several hundred Myr. ESO
006-001 is an example of a transition dwarf; a galaxy dominated by old stars
but one that has experienced limited recent star formation in a swath near the
center. No H i gas is detected at the location of the optical galaxy in spite
of the evidence for young stars. Intriguingly, an H i cloud with a similar
redshift is detected 9 kpc away in projection. Otherwise, ESO 006-001 is a
galaxy in isolation with its nearest known neighbor IC 3104, itself a dwarf, at
a distance of ~ 500 kpc.Comment: 13 pages, 9 figures, accepted at Ap
MIGHTEE-HI: the HI Size-Mass relation over the last billion years
We present the observed HI size-mass relation of galaxies from the
MIGHTEE Survey Early Science data. The high sensitivity of MeerKAT allows us to
detect galaxies spanning more than 4 orders of magnitude in HI mass, ranging
from dwarf galaxies to massive spirals, and including all morphological types.
This is the first time the relation has been explored on a blind homogeneous
data set which extends over a previously unexplored redshift range of , i.e. a period of around one billion years in cosmic time. The sample
follows the same tight logarithmic relation derived from previous work, between
the diameter () and the mass () of HI discs. We measure
a slope of , an intercept of , and an
observed scatter of dex. For the first time, we quantify the intrinsic
scatter of dex (), which provides a constraint
for cosmological simulations of galaxy formation and evolution. We derive the
relation as a function of galaxy type and find that their intrinsic scatters
and slopes are consistent within the errors. We also calculate the relation for two redshift bins and do not find any evidence for
evolution with redshift. These results suggest that over a period of one
billion years in lookback time, galaxy discs have not undergone significant
evolution in their gas distribution and mean surface mass density, indicating a
lack of dependence on both morphological type and redshift.Comment: 10 pages, 5 figures, accepted for publication in MNRA