H. van Woerden's research while affiliated with University of Groningen and other places
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Publications (135)
Environmental effects may be of great importance to the structure and evolution of galaxies. Sullivan and collaborators (1981, AJ 86 , 919) find that the ratio between HI content and luminosity of galaxies tends to be smaller in regions of high galaxy density than elsewhere. It is not quite clear what processes reduce the gas content (or enhance th...
We report the results of HI observations of eleven gas-rich SO/SOa galaxies with the Westerbork Synthesis Telescope. The majority of these galaxies have most of their hydrogen outside the optical body, in annular configurations with diameters ~2 times the optical. These outer gas rings are often clumped, incomplete, and in approximately circular mo...
At Westerbork, we have mapped the distribution and motions of HI in about twenty gas-rich SO and SO/a galaxies, with resolutions of order 30 arcsec. Gas-rich SO's often have most of their HI in an outer ring, with diameters between 0.9 and 2.5 times the optical (D 0 ). Assuming circular shape and motions for this ring, radius R, and a spherical dis...
IC 10 is seen optically as a patchy nebulosity, approximately 3 × 4 arcmin in size, possibly heavily obscured due to its low (−3°) Galactic latitude. De Vaucouleurs and Freeman (1972) have classified it as a Magellanic barred irregular. With a heliocentric radial velocity of −350 km/sec, its distance is uncertain, and various investigators have pla...
Maps with 0′.5 resolution are presented of the distribution of neutral hydrogen in two galaxies. The barred spiral NGC 5383 contains much hydrogen, in strong differential rotation, in its outer parts; some H I concentrations with possibly anomalous velocities are observed in the regions of bar and nucleus. In the giant Scd spiral M101, the H I dist...
The IAU Working Group on Historical Radio Astronomy (WGHRA) was formed
at the 2003 General Assembly of the IAU as a Joint Working Group of
Commissions 40 (Radio Astronomy) and 41 (History of Astronomy), in order
to: a) assemble a master list of surviving historically-significant
radio telescopes and associated instrumentation found worldwide; b)
do...
During the Rio General Assembly we held the following meetings of the Working Group: a Business Meeting, a Science Meeting on ``The Development of Aperture Synthesis Imaging in Radio Astronomy'', and a Science Meeting on ``Recent Research''.
The Working Group was formed at the IAU XXV General Assembly in Sydney,
2003, as a joint initiative of Commissions 40 Radio Astronomy and
Commission 41 History of Astronomy, in order to assemble a master list
of surviving historically-significant radio telescopes and associated
instrumentation found worldwide, and document the technical
specificati...
We have measured the amount of kinematic substructure in the Galactic halo using the final data set from the Spaghetti project, a pencil-beam high latitude sky survey. Our sample contains 101 photometrically selected and spectroscopically confirmed giants with accurate distance, radial velocity and metallicity information. We have developed a new c...
A lower limit to the distance of the high-velocity cloud (HVC) complex A of 4 kpc (z > 3 kpc) is derived. The HVC is detected toward the Seyfert galaxy Mrk 106 in Mg n ΛΛ2796, 2803 absorption spectra taken with Hubble Space Telescope (HST) proving that Mg+ is present in the cloud. It is not detected in the Mg ii spectra of two stars, PG 0859 + 593...
We report on observations of the J = 1-0 line of 12CO at 115 GHz toward several high-velocity H I clouds (HVCs). High angular resolution observations at 21 cm show the presence of dense cores with N(H I) = (2-4) × 1020 cm-2 and n(H )=30-80D cm-3. We observed the CO line toward six of the densest HVC cores. No12CO emission is detected down to a best...
We derive a lower limit for the distance of the high-velocity cloud (HVC) complex H, which is a structure covering 480 square degrees on the sky and is centered on l = 131°, b = 1°. Considering the uncertainties in the derivation of stellar distances, we find that the distance to the HVC is certainly larger than 3.4 kpc, probably larger than 5 kpc,...
We present a moderate resolution H I map of the amorphous galaxy NGC 4670. Our previous lower resolution data had shown a symmetric H I distribution centered on the single supergiant H II region and highly concentrated to the center of the galaxy. We now resolve the central H I distribution into three clouds, with the eastern cloud located on the c...
We report the first determination of a distance bracket for the high-velocity cloud (HVC) complex C. Combined with previous measurements showing that this cloud has a metallicity of 0.15 times solar, these results provide ample evidence that complex C traces the continuing accretion of intergalactic gas falling onto the Milky Way. Accounting for bo...
A full understanding of the High Velocity Clouds (HVCs) is still lacking
more than four decades after their discovery. Determining the clouds'
locations in relation to the Galaxy is an important constraint on
hierarchical assembly models of galaxies in a Λ-CDM universe.
However, quantifying physical cloud properties such as mass and size
have been...
This contribution reports results of recent absorption-line studies on La Palma and reviews earlier work done elsewhere. CaII
has been found in absorption in five HVCs, mostly against extragalactic background sources. The CaII/HI ratios differ strongly,
from 0.002 to 0.1 times solar, suggesting different origins of HVCs. Nondetections of CaII absor...
The Dwingeloo 25-m telesope, inaugurated in 1956, has played a major role in research for half a century. We trace its history back to its conception in 1944, and summarize its main achievements. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
We present firm evidence that one of the major high velocity clouds (HVCs), Complex A, lies in the Milky Way Halo, at a vertical
distance z=3–7 kpc from the Galactic plane. For clouds MII/MIII, Danly et al. and Keenan et al. had already found z<5 kpc. We further report that the metallicity in the largest HVC, Complex C, is at least 0.1 solar. CaII/...
We review the methods for determining the distances and metallicities of high-velocity clouds. A short summary is given of
several indirect methods, but we concentrate on the absorption-line method, which is based on the detection and non-detection
of interstellar absorption lines in the spectra of background and foreground stars, as well as of ext...
The birth of Dutch radio astronomy can be rather precisely dated to 15 April 1944, when H.C. van de Hulst presented the results of his theoretical research into the origin of radio waves from space. We have investigated the events leading up to the momentous suggestion that hydrogen emission at 21 cm ought to be detectable. Both published material...
On the occasion of the retirement of Ulrich Schwarz, a symposium was held in Groningen in May of 1996, celebrating his contributions to the study of the int- stellar medium, including his work on the high-velocity clouds. The coming together of many specialists in the latter ?eld prompted the idea of compiling a book c- taining their contributions,...
▪ Abstract High-velocity clouds (HVCs) consist of neutral hydrogen (HI) at velocities incompatible with a simple model of differential galactic rotation; in practice one uses vLSR 90 km/s to define HVCs. This review describes the main features of the sky and velocity distributions, as well as the available information on cloud properties, small-sca...
We present UBVJHKHalpha and HI data of the irregular galaxy NGC 2366. It is a normal boxy-shaped disk seen at high inclination angle. We do not see any unambiguous observational signature of a bar. There is an asymmetrical extension of stars along one end of the major axis of the galaxy, and this is where the furthest star-forming regions are found...
We show 21-cm line profiles in the direction of stars and extragalactic objects, lying projected on high- and intermediate-velocity clouds (HVCs and IVCs). About half of these are from new data obtained with the Effelsberg 100-m telescope, about a quarter are extracted from the Leiden-Dwingeloo Survey (LDS) and the remaining quarter were observed w...
Models of the chemical evolution of the Milky Way suggest that the observed abundances of elements heavier than helium ('metals') require a continuous infall of gas with metallicity (metal abundance) about 0.1 times the solar value. An infall rate integrated over the entire disk of the Milky Way of approximately 1 solar mass per year can solve the...
We present high-resolution interferometric data of the inner 30′ of the H I gas of the irregular galaxy NGC 4449. In addition to the previously known two counter-rotating gas systems, the H I exhibits an unusual ring morphology and high velocity dispersions in the outer part of the optical galaxy. In addition the position angle and inclination of t...
The high-velocity clouds of atomic hydrogen, discovered about 35 years ago, have velocities inconsistent with simple Galactic rotation models that generally fit the stars and gas in the Milky Way disk. Their origins and role in Galactic evolution remain poorly understood, largely for lack of information on their distances. The high-velocity clouds...
We find evidence for a hitherto unknown component of the Milky Way: infalling gas with low heavy element abundances. Infall of metal-poor matter has been the preferred solution to the long-standing ``G-dwarf problem'', the fact that the abundance distribution of unevolved stars is narrower than expected in a simple model (e.g. Pagel 1997). Our conc...
The study of high-velocity clouds has progressed much since the appearance of the review article by Wakker & van Woerden (1997), less than two years ago. Much of this progress is described in these workshop proceedings. Here we update the review article, summarizing the topics discussed at the workshop as well as covering the recent literature. We...
NGC 4449 is a bright (B = 9.5), nearby (4 Mpc) irregular galaxy with a high surface brightness and strong star-formation activity; for photos see Hunter and Gallagher (1989). Using the Effelsberg 100-meter dish, van Woerden et al. (1975) - and later also Bajają et al. (1994) - found its HI distribution to extend, at the level 2 × 10 ¹⁹ atoms cm ⁻²...
Nature and origin of the high-velocity clouds (HVCs) remain enigmatic after thirty years (Wakker & van Woerden 1997, ARA
&
A, 35, 217), owing to lack of distance information. Hypotheses range from supernova shells at 100 pc to intergalactic clouds at 1 Mpc. On statistical grounds, Blitz et al. (1996, BAAS, 28, 1349) claim that the HVCs are “remnant...
We present observations of the (field of the) Seyfert galaxy Mark 290, which probes the high-velocity cloud (HVC) complex C, one of the largest HVCs (Wakker & van Woerden 1991). We find that this object has a metallicity of 0.094+/-0.020^{+0.022}_{-0.019} times solar. A semi-theoretical upper limit of 30 kpc is set to its distance; D. Combined with...
Distance and metallicity hold the key to our understanding of the
physical properties and origins of HVCs. We review the problems and
results of determinations of distance and metallicity based on the
presence or absence, and strength, of appropriate absorption lines in
the spectra of stars at different distances and of extragalactic
background sou...
Nature and origin of the high-velocity clouds (HVCs) remain enigmatic after thirty years (Wakker & van Woerden 1997, ARA&A , 35 , 217), owing to lack of distance information. Hypotheses range from supernova shells at 100 pc to intergalactic clouds at 1 Mpc. On statistical grounds, Blitz et al. (1996, BAAS , 28 , 1349) claim that the HVCs are “remna...
We present observations of the (field of the) Seyfert galaxy Mark290, which probes the high-velocity cloud (HVC) complex C, one of the largest HVCs. We find that this object has a metallicity of 0.094pm0.020(+0.022-0.019) times solar. We determine a lower limit to its distance of 5 kpc (z>3.5 kpc). If the gas is in thermal equilibrium with a hot ha...
Westerbork HI synthesis observations are presented for the directions of
the stars 4 Lac and HD 135485. Interstellar absorption lines at high
velocities had been reported in the UV spectrum of 4 Lac, setting an
upper limit of 1.2 kpc on the distance of the associated, small HI cloud
(Bates et al. 1990, 1991). The Westerbork observations show that t...
We present interferometric H I 21 cm line observations of the extended gas around the irregular galaxy NGC 4449 covering 67' on the sky at a resolution of ~1'. The main star-forming body of NGC 4449 is relatively normal for a Magellanic irregular galaxy, but the galaxy is unusual in that it has two counterrotating gas systems and H I that extends t...
NGC 4449 is a nearby (5 Mpc) irregular galaxy with a high rate of star formation and intricate HII structures. The HI disk extends over 10 optical diameters; its inner parts are counter-rotating with respect to the outer disk (Van Woerden H, Bosma A, Mebold U 1975, in "La Dynamique des Galaxies Spirales", ed. Weliachew L, Paris: CNRS, p. 483; Bajaj...
We present firm evidence that one of the major high velocity clouds (HVCs), Complex A, lies in the Milky Way Halo, at a vertical distance z = 3 - 7 kpc from the Galactic plane. For clouds MII/MIII, Danly et al. and Keenan et al. had already found z < 5 kpc. We further report that the metallicity in the largest HVC, Complex C, is at least 0.1 solar....
NGC 4449 is a nearby galaxy that has long been considered to be representative of normal giant Magellanic irregulars with an unusually large, quiescent disk. We present a VLA mosaic of the extended HI disk around NGC 4449 that shatters this preconception. Our data show NGC 4449 to contain a bright central condensation of gas associated with the opt...
We report the first detection of Ca II H and K absorption in the
high-velocity cloud complex C, the largest HVC. Absorption is detected
in the spectra of the quasar PG 1351+640 and of the Seyfert galaxy Mark
290, at velocities of -163 and -137km/s (see fig.2). The implied Ca+
abundances are about 2x10^-8^, or about 0.01 times the total solar
Calciu...
High-velocity clouds (HVCs) are HI clouds deviating strongly from the general Galactic rotation. Their distances, and hence origins, have long remained unknown. However, three major complexes are now known to lie at z > 1 kpc, while two smaller clouds are closer to the plane (Wakker et al. 1995). These incomplete results still allow a variety of or...
Table 1 summarizes results of programs to determine distances and metallicities of high-velocity clouds (s, HVCsee Wakker 1991, IAU Symp 144, 27 for a general review). Reliable absorption is reported for one stellar probe (17-38 B2182), giving a distance D<5 kpc for complex M. Other results are controversial (BT Dra) , uncertain( HD 135485) or atyp...
Table 1 summarizes results of programs to determine distances and metallicities of high-velocity clouds (HVCs, see Wakker 1991, IAU Symp 144, 27 for a general review). Reliable absorption is reported for one stellar probe (BD+38 2182), giving a distance D <5kpc for complex M. Other results are controversial (BT Dra), uncertain(HD 135485) or atypica...
This paper presents results of a program to derive distances of high-velocity clouds (HVCs) through measurement of absorption in the CaIIH and K lines. The problems of the method and their solutions are discussed in detail. A probable detection of absorption toward the Seyfert galaxy Mark106 is reported, which gives a Ca^+^ abundance of (17+/-6)x10...
We present short 21-cm line observations of about 50 spiral galaxies,
made with the Westerbork Synthesis Radio Telescope. They form the first
stage of a two-stage project to study the relation between the shape of
extended rotation curves and galaxy properties, such as luminosity and
morphological type. In this first stage, one-dimensional informat...
The Sa-type galaxies NGC 1169 and NGC 3898 were mapped in the 21-cm H I
line at Westbrook with a spatial resolution of about 30 sec and a
velocity resolution of 40 km/s. A comparison of the H I distributions of
the 3 Sa galaxies mapped by us (NGC 1169 and 3898, and IC 5267) with
those of 6 S0/a and RSB0/a, and 9 Sb-type spirals shows no clear
diffe...
High resolution IUE spectra of sdB and HBB stars in the direction of the
concentration of neutral hydrogen gas at high-velocity named Complex C
have been obtained. The interstellar absorption line profiles are
compared with Effelsberg HI 21-cm emission profiles. Since the distances
to the stars are known from spectroscopic investigations, firm lowe...
The catalogue is a compilation of magnitudes at 1.6um, 21cm velocity
widths, and related data on 307 nearby galaxies. (1 data file).
Results of the mapping of the blue gas-rich S0 galaxy NGC 5102 in the 21-cm H I line with a spatial resolution of 34 x 37 arcsec (delta(alpha) x Delta(delta)) and a velocity resolution of 12 km/s are presented. The H I distribution has a pronounced central depression of 1.9 kpc radius, and most of the H I is concentrated in a 3.6 kpc wide ring with...
We present new interferometric H I and optical observations of three
amorphous galaxies, systems with a smooth, high surface brightness but
an asymmetrical distribution of light. All three galaxies are forming
stars and have LMC-like emission-line ratios, low dust content, and high
H I velocity dispersions. NGC 1140 has a boxy inner morphology with...
The authors report here on an ongoing program to determine the distribution and physical properties of the molecular gas component of the ISM in lenticular galaxies. For the present sample they infer the H2 mass to be greater than the H I mass. Through modelling it is found that the molecular gas is distributed either in a ring or a centrally peake...
Amorphous galaxies are characterized by smooth light distributions and bright central young-star complexes. H I observations of three amorphous galaxies (NGC 1140, 1800 and 4670) show extensive gas distributions, with high central concentrations. The rotation periods are of order 109yr.
CO emissions are investigated in 11 S0 galaxies in offset and
central-beam positions, and the results are employed in a model for
fitting synthetic spectra to the data. In all the galaxies the emission
is partly resolved, except in NGC 1326 and some other S0s where the CO
emission extends through other parts of the disk. The model indicates
that a...
The first complete catalog of high-velocity clouds (HVCs) is presented,
followed by a classification of these clouds into complexes and
populations. The catalog forms the basis for comparisons with
theoretical models. The following conclusions are drawn: (1)
Differential Galactic rotation makes a large contribution to observed
radial velocities, so...
Optical absorption spectroscopy is presented for the Ca II K and H lines
along the sight line to the quasar PKS 0837 - 120, which lies in the
direction of a high-velocity cloud (HVC) detected in H I 21-cm emission
at V(LSR) = +105 km/sec. The data show Ca II absorption due to the HVC
as well as a lower-velocity interstellar component. The column de...
It is considered that the H I velocity fields in most early-type galaxies can be described by circular rotation, sometimes in a considerably warped H I distribution. The derived rotation curves are essentially flat, sometimes out to 10 optical disk scale lengths, denoting the presence of massive dark halos, which is substantiated by detailed disk/b...
The distribution and motions of the H I gas in the SB0 galaxy NGC3941
and the peculiar Virgo Cluster S0 galaxy NGC4694 have been mapped.
Optically, NGC3941 is a normal-looking SB0 galaxy. NGC3941 is a
relatively gas-rich lenticular. The H I distribution shows a pronounced
central hole, an incomplete circular inner ring of 5 kpc radius, and an
outer...
The NGC 3619, 3626, and 3900 galaxies were mapped in the 21-cm H-I line
with a spatial resolution of about 30 arcsec and a velocity resolution
of 40 km/s. An encounter with the nearby spiral NGC 3625, or a merge
with a dwarf galaxy, some 0.5 to 10 to the 9th years ago may explain the
optical and H-I properties of NGC 3619. The H-I distribution of S...
This contribution reports results of recent absorption-line studies on La Palma and reviews earlier work done elsewhere. CaII has been found in absorption in five HVCs, mostly against extragalactic background sources. The CaII/HI ratios differ strongly, from 0.002 to 0.1 times solar, suggesting different origins of HVCs. Nondetections of CaII absor...
During the final corrections and the preparation of printing plates, a part of Eq. (1) on p 22 was accidentally deleted. The complete line should read as follows: M_i_(M_sun_) = 2356 10^5^ D^2^[Mpc^2^] F(v)dv[Jy km s^-1^], (1)
The gas-rich RSB0/type galaxies NGC 1291 and NGC 5101, and the
early-type Sa galaxy IC 5267 were mapped in the 21-cm H I line with a
spatial resolution of about 40arcsec and velocity resolutions of 10, 13
and 26 km s-1 respectively. H I was also detected in the
spiral galaxy IC 5267 Å. It is argued that the gas found in these
early-type disk galaxi...
The 21-cm line observations of a sample of 33 bright southern galaxies
have been used to derive their H I properties by the means of a
model-fit procedure. The observed line-profiles were reconstructed by
the model-fit, and the fit with the smallest rms value was taken as the
result. Effective H I diameters were determined along the line of
maximum...
The distribution of H I in Sex A is investigated by means of
interferometric observations obtained at velocity resolution 6.2 km/s
with the D configuration of the VLA on August 2, 1984. The results are
presented in extensive graphs and contour maps and discussed in detail.
The H I distribution is characterized by (1) two dominant clumps showing
rec...
The gas-rich S0 galaxy NCC 4203 was mapped in the 21-cm H I line with a
spatial resolution of 24" x 44" (α x δ) and a velocity
resolution of 33 km s-1. The H I gas distribution shows an,
almost circular, inner ring, in circular rotation in the plane of the
optical disk, and an extended outer component. A warped-disk model for
the H I distribution i...
Interferometric H I observations of the dwarf irregular galaxy Sextans A are presented. The H I distribution shows a strong correspondence with the optical structure, and the velocity field is dominated by solid body rotation. However, the velocity field is not aligned with the optical axis of symmetry, and this renders the mass distribution analys...
This paper reviews the high-resolution observations of interstellar
calcium and sodium absorption in the spectra of stellar and
extragalactic probes, aiming at determination of the distances of
high-velocity clouds. Calcium K-line absorption has been found in most
or all of the HVCs sampled with extragalactic probes, showing the
presence of substan...
The distribution of H I in the normal, barred lenticular galaxy NGC 4262
in the Virgo Cluster has been mapped at a resolution of
13arcsec×51arcsec. The gas is confined to a narrow ring,
apparently in circular rotation about the galaxy center. The ring has a
diameter about twice the optical diameter of the galaxy, and is inclined
by at least 50° (an...
An overview of all major aspects of galactic astronomy is presented. The
subjects considered include: the history of galactic research; galactic
rotation; the large-scale distributions of matter, of old and young
stellar populations, and of the atomic, molecular, and high-energy
components of the interstellar medium; small-scale structure in the ga...
The conference presents papers on the structure of star forming regions,
the stellar content of young groups, the evolution of massive stars, an
extragalactic perspective on star formation and the scientific work of
Adriaan Blaauw. Particular attention is given to the nearest molecular
clouds, the distribution and motion of young nearby stars as a...
Recent results, partly unpublished, are reviewed regarding attempts to
understand the High-Velocity Clouds (HVC), discovered in the 21-cm line
of neutral hydrogen. Much progress has been made in the study of their
properties, and prospects are brightening that the problem of their
distances, which holds the key to their understanding, may soon be
s...
My paper is the final contribution to our profile of Adriaan Blaauw. Jan Oort has summarized his scientific work and Walter Fricke his contributions to the establishment of the cosmic distance scale. Jean-Pierre Swings and Edith Müller have outlined his role in the IAU and in the international astronomical community. Lo Woltjer has discussed his wo...
Unfortunately, the text of this review paper is not available. For recent reviews, we refer the reader to the following papers:
Twenty years after their first discovery at Dwingeloo (Muller, Oort and Raimond 1963), the nature and origin of high-velocity clouds (HVCs) remain enigmatic. Yet, much important progress has been made in the study of their properties, and prospects are brightening that the problem of their distances, which holds the key to their understanding, may...
In June 1983 the Astronomical Institute of the State University of Groningen, founded by Kapteyn about 100 years ago, celebrated its one-hundredth anniversary. At the suggestion of its Chairman, R.J. Allen, the Kapteyn Institute invited the International Astronomical Union to mark the centenary by holding a Symposium on "The Milky Way Galaxy". The...
Citations
... These all lie in the outer border of the domain. The highest column density clouds are found in the range of v LSR that traditionally corresponds to LVCs (±35 km/s, chapter by Albert & Danly in van Woerden et al. 2004). Clouds within this velocity range exhibit similar range of N HI in the North and South regions. ...
... Applying the model to our galaxy permits a quantification of the previous results. The IAU standard values for the solar system (r 0 = 8.5 ± 0.5 kpc, u 0 = 220 ± 20 km s −1 ) and for the position of maximum circular speed (r max = 0.5 ± 0.1 kpc, u max = 240 ± 20 km s −1 ) established in van Woerden et al. 1985 initially imply n = −0.03 ± 0.04. ...
... Reviews concerning OB associations throughout the Local Group include [60], [97], and [103]. In addition there are conference proceedings that contain material on OB associations: [20], [33], [79], [100], and [132]. For more background on the historical development of OB association research we refer to [9], [30], [49], and [150]. ...
Reference: OB Associations
... Attempts to prevent the destruction of Stanford University's solar array and five 60-ft dishes were unsuccessful, but the pillars at the solar array containing the chiselled signatures of many of the world's foremost radio astronomers were preserved and transferred to the NRAO site at Green Bank. Kellermann et al. (2011) report other successes: ...
![[object Object]](https://i1.rgstatic.net/ii/profile.image/278662617288714-1443449753355_Q64/Wayne-Orchiston-2.jpg)
... m is not closed and that the ISM has been diluted by infalling gas with a substantial underabundance of heavy elements, as suggested by Jura et al . (1996). There is growing evidence that at least some of the high-velocity gas currently observed to be falling into the Galaxy has heavy-element abundances of ca. 10% solar level (Richter et al . 2000;Wakker et al . 1999), lending support to the dilution hypothesis. ...
... The only direct method uses the presence or absence of interstellar absorption lines at the HVC's velocity in spectra of stars at different distances. Presence of absorption shows the HVC to lie in front of the star; absence places it beyond, provided the expected absorption is well above the detection limit 11 . Blue stars are best, since their spectra contain few confusing stellar lines. ...
... We presented some evidence for this idea in [1] and it will become apparent in Part 2 that these same imprints are responsible for the observed HI structures. All cosmic structures follow a general plan as demonstrated by the observed distributions of their counts and sizes, [2]. We found that th