21-cm line studies of spiral galaxies. II. The distribution and kinematics of neutral hydrogen in spiral galaxies of various morphological types.

“HI measurements have played a fundamental role in establishing the flatness of rotation curves in spiral galaxies (e.g., Bosma 1981a, b).”

“This is very different from the situation in local galaxies, where the gas only extends up to a few times the extension of the light (Bosma 1981).”

“This later became known as the ‘tiltedring’ description for ‘kinematic warps’ and many more galaxies have been shown to have such deviations using this method (e.g. Bosma, 1981).”

“Radio observations (Bosma 1981) have shown that the surface density of H I gas is proportional to the projected surface density of the total mass, which for a perfectly flat rotation curve would imply a 1/R distribution.”

“d velocity curves." —M. Milgrom [16] This simple statement has a variety of testable consequences. Property 5. Flat Rotation Curves The striking flatness of the rotation curves of spiral galaxies [89,90] was an animating motivation for both dark matter and MOND. That they are observed to be so is thus not an a pri…”

“Though C© 2011 The Authors, MNRAS 414, 3617–3626 Monthly Notices of the Royal Astronomical Society C© 2011 RAS no physical bar is present in the simulation, these are features commonly observed in the velocity fields of barred galaxies (e.g. Bosma 1981; Hernandez et al. 2005).”

“A similar fraction of galaxies has lopsided HI distributions or kinematic asymmetries (Baldwin et al., 1980; Bosma, 1981; Richter & Sancisi, 1994; Haynes et al., 1998; Swaters et al., 1999).”

“In NGC 4123, the gas streamlines elongated along the bar cause the isovelocity contours to twist and run more closely along the bar, producing the S-shaped isovels characteristic of barred galaxies (Bosma 1981).”

“It is known from observations that the orbits of the disk material in spiral galaxies without large bars have a comparably low ellipticity (e.g. Bosma 1981; Schoenmakers et al. 1997), such that it is a good approximation to treat them as being circular.”

“…around luminous galaxies comes from stellar velocity dispersions and rotation curves in the outer parts of spiral galaxies (Faber & Gallagher 1979; Bosma 1981; Trimble 1987); and 1Based on observations with the Canada-France-Hawaii Telescope which is operated by the National Research Council of…”

“…(moment 0), mean velocity (moment 1) and line velocity width (moment 2) maps of the detected lines were created from the cleaned, continuum-subtracted CO data cubes using the masked moment technique as described by Dame (2011, see also Bosma 1981a,b; van der Kruit & Shostak 1982; Rupen 1999).”

“The isovelocity contours in Figure 1e show a number of kinks and bends, and the individual channel maps show features with an S shape, as opposed to the classical V shape observed in regularly rotating spiral galaxies (see e.g., Bosma 1981).”

“This was noted for spiral galaxies by Bosma (1981) and further investigated by Hoekstra et al. (2001).”

“…CO, the isovels do not run parallel to the minor axis as would be the case for purely circular motions, but show a deviation characteristic of gas streaming along the preferred major axis of the bar, as expected (Roberts, Huntley & van Albada 1979) and observed (e.g. Bosma 1981) in barred galaxies.”

“Another source of uncertainty comes from strong warps and other types of nonaxisymmetric distortions in the HI disk, which are known to be present in many disk galaxies (e.g., Baldwin et al. 1980; Bosma 1981; Lewis 1987; Richter & Sancisi 1994; Haynes et al. 1998).”

“…Hispano Alemán (CAHA) at Calar Alto, operated jointly by the MaxPlanck Institut für Astronomie and the Instituto de Astrofı́sica de Andalucı́a (CSIC) ⋆⋆ National Science Foundation (USA) International ResearchFellow Roberts 1966; Rogstad & Shostak 1972; Bosma 1978, 1981a,b; Rubin et al. 1980).”

“, of the values the energy of an atom can take), and the ability to predict exactly the outcome of a measurement, replaced by the ability to predict only probabilities.(18) In the case of relativity, the abandonment of the concept of absolute time is an example.”

“Indeed, the parameters of mass models are not constrained by the flat part but by the rising part of RCs. Bars in galaxies have very different masses, lengths, axial ratios, colour distributions, gas content, pattern speeds, shapes and kinematics.”

“…and the dynamical properties of cosmic structures over a large range of scales, from the rotation curves of spiral galaxies (Rubin et al. 1980; Bosma 1981; Persic et al. 1996) through the inner dynamics of galaxy clusters (Zwicky 1937; Clowe et al. 2006) up to the cosmological scales probed…”

“For disc galaxies (Sb and later types), the rotation curve is generally described by an inner rising part (nearly solid body) and an outer flat part (e.g. Bosma 1981; Begeman 1987; Swaters et al. 2009).”

“The rotation curves of spiral galaxies become approximately fl at at large radii ( Rubin et al. 1978 ) and remain so well beyond the extent of the observed luminous mass ( Bosma 1981 ) .”

“This signature could be caused by departure from axisymmetry in the mass distribution, such as an oval distortion and is indicative of a bar instability that may drive gas inflow (Bosma 1981).”

“The discovery, made in the 1970s (Rogstad & Shostak 1972; Roberts & Whitehurst 1975; Bosma 1978; Bosma 1981), that rotation curves remain flat till the last measured points, well outside the optical discs, provided the decisive evidence for the presence of large amounts of dark matter in galaxies.”

“…which resulted in the initial discovery of DM (Rubin, Thonnard & Ford C© 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society Downloaded from https://academic.oup.com/mnras/article-abstract/439/1/659/982796 by guest on 28 July 2018 1978; Bosma 1981).”

“The earliest hints for dark matter arose from its gravitational effects on galaxies, explaining the observed flatness of rotation curves (Rubin and Ford, 1970; Roberts and Whitehurst, 1975; Rubin et al., 1980; Bosma, 1981).”

“Bosma (1981a) and Schoenmakers et al. (1997) have shown that the orbits of material within spiral galaxies have low ellipticity.”

“The oval distortion, identi®ed kinematically in early H i studies (Bosma et al. 1977; Bosma 1981) and evident in deep optical exposures (Arp 1977) and subsequent H i maps (Pedlar et al. 1992), is elongated along PA ,1308 and has dimensions of 3:3 ´ 2:1 arcmin2 (12.9 ´ 8.2 kpc2).”

“In the local group, including the Milky Way, the three dominant spirals are warped (Roberts, 1966; Rogstad, Wright & Lockhart, 1976; Newton & Emerson, 1977) and among nearby galaxies they are common (Sancisi, 1976; Bosma, 1981).”

“In the inner disk one can see a slight ““ oval distortion, ÏÏ which corresponds to the bar region The(Bosma 1981). apparent streaming motions in the bar are very small (¹10 km s~1), although this may just be a projection e†ect.”

“It has been shown that on galactic scales MOND can explain many phenomena at least as well as CDM (Sanders & McGaugh 2002).”

“Long ago Bosma (1981a) pointed out that the dynamical mass in spirals is known to be well correlated to a multiple of the detected HI (see also Hoekstra et al. 2001).”

“5 (Broeils & van Woerden 1994) even at an Hi column density above ≥ 1019 atoms cm−2 in irregulars and spirals (Bosma 1981a,b; Huchtmeier et al. 1981).”

“H i in galaxies is well documented to lie in rotationally supported discs that extend notably beyond optical discs from stellar emission (e.g. Bosma 1981a).”

“Additionally, the kinematical major and minor axes are not orthogonal, characteristic of oval (A color version of this figure is available in the online journal.) distortions (such as bars) or warping (Bosma 1981).”

“Bosma (1978, 1981) found that the ratio of total mass surface density to HI surface density is roughly constant in the outer parts of galaxies.”

“Decomposition of a rotation curve into several mass components such as a bulge, disk and dark halo has been extensively applied to observed data (Bosma 1981a; Kent 1986; Sofue 1996).”

“…& Gottesman 1995; (16) Newton 1980; (17) Broeils 1992; (18) van Zee, Skillman, & Salzer 1998; (19) Walter & Brinks 2001; (20) Shostak 1987; (21) Bosma 1981a, 1981b; (22) Ott et al. 2001; (23) Young & Lo 1996; (24) Irwin & Seaquist 1991; (25) Begeman 1989; (26) Martimbeau, Carignan, & Roy…”

“Like many spiral galaxies in the universe, the warp of the Milky Way (MW) was detected by neutral hydrogen (H I) gas many years ago (Kerr 1957; Bosma 1981; Briggs 1990; Nakanishi & Sofue 2003; Levine et al. 2006b).”

“For more than half a century, it has been known that the Hi disk of our own Galaxy is warped in the outer parts (Burke 1957; Kerr 1957), and it later became clear that many spiral galaxies have warps (e.g., Sancisi 1976; Bosma 1981b).”

“The 3D imaging data products (moment maps and positionvelocity diagrams) used in this work were created from the cleaned, continuum-subtracted CO data cubes using the masked moment technique as described by Dame (2011, see also Bosma 1981a,b; van der Kruit & Shostak 1982; Rupen 1999).”

“As for SMD profiles, Bosma (1981b) used two methods, each described by Nordsieck (1973) and Shu et al. (1971), to derive them directly from RCs.”

“In these regions the rotation curves are approximately flat and the total density profiles close to isothermal (Bosma 1978, 1981; van Albada et al. 1985; Gavazzi et al. 2007; Cappellari et al. 2015, hereafter C15).”

“Stellar disks tend to be embedded in much larger HI disks (Bosma 1981; Broeils & Rhee 1997; Begum et al. 2005), showing that while there are baryons in the outskirts of galaxies, they are not being converted into stars efficiently.”

“In particular, the analysis of rotation curves in the outer parts of galaxies based on neutral hydrogen observation has led to the firm establishment of dark matter in galaxies (e.g. Rubin et al. 1980; Bosma 1981; van Albada et al. 1985, and many others).”

“These surveys are complemented with the spatially resolved H i images obtained using interferometers to trace the large scale dynamics of the galaxies (e.g. Bosma 1981; Fisher & Tully 1981; Meyer et al. 2004; Oosterloo, Fraternali & Sancisi 2007; de Blok et al. 2008; Walter et al. 2008).”

“Kinematics in the outer parts of latetype galaxies can often be observed from the presence of neutral hydrogen (e.g., Bosma 1981; van Albada et al. 1985; Persic et al. 1996; Noordermeer et al. 2007).”

“…spectroscopy (Rubin & Ford 1970), and soon thereafter radio observations in the 21cm line of neutral hydrogen (H I) revealed that rotation curves remain flat over many multiples of the optical radius (Warner et al. 1973; Bosma 1978, 1981a, 1981b; van der Kruit & Bosma 1978; Bosma et al. 1981).”

“The overall profile is fairly typical for spirals (type Sa–Sc) with a steep initial rise within the inner few kpc, beyond which the velocity plateaus (Rubin, Thonnard & Ford 1980; Bosma 1981a,b; Rubin et al. 1982, 1985).”

“The halo is also known to play a crucial role in keeping the net rotation curve nearly flat at large radii, and in fact the existence of dark matter halos in galaxies was deduced from such flat rotation curves (Rubin et al. 1980; Bosma 1981; van Albada et al. 1985).”

“This phenomenon has been revealed in the neutral gas component, through HI observations (e.g.Sancisi 1976, Bosma 1981, Briggs 1990, Garcı́a-Ruiz, Sancisi & Kuijken 2002), and in a lesser extent through optical and infrared observations (e.g. Sánchez-Saavedra, Battaner & Florido 1990, de Grijs…”

“…role in a major astronomical mystery − why do their rotation curves (RCs) go flat in their outskirts instead of following the expected Keplerian decline beyond the extent of their luminous matter (e.g. Babcock 1939; Rubin & Ford 1970; Rogstad & Shostak 1972; Roberts & Whitehurst 1975; Bosma 1981)?”

“Nonetheless, the majority of spiral galaxies have H I RCs that are relatively flat in their outer parts (e.g. Bosma 1978, 1981a,b), although the possibility that many RCs become Keplerian within r ∼ 3ropt cannot be ruled out (Honma & Sofue 1997).”

“The kinematic minor axis is not perpendicular to the inner kinematic major axis, this is typically an indication of a bar structure (Bosma, 1981), which is consistent with the optical classification of this galaxy.”

“A similar fraction of galaxies ≈30%−50% has lopsided HI distributions or kinematic asymmetries (Baldwin et al. 1980; Bosma 1981; Richter & Sancisi 1994; Swaters et al. 1999; Kornreich et al. 2000).”

“Recently,Meurer et al.(2013) showed that hypothesis can explain how HI traces dark matter in the outer parts of galaxies (the so called “Bosma relation”;Bosma 1981) by using a single-fluidQ model.”

“This is suggestive of an oval distortion in the potential with the gas moving along elliptical orbits (cf. Bosma 1981).”

“It has been pointed out by Bosma (1978, 1981) that in samples of galaxies, the ratio between the dark matter and HI surface density is roughly constant well after the optical disk( ee also Carignan et al. 1990; Broeils 1992; Hoekstra et al. 2001).”

“From the 1970s onward, it has been taken as a serious problem appearing on galactic and cosmological scales (Rubin & Ford 1970; Rogstad & Shostak 1972; Roberts & Whitehurst 1975; Bosma 1981) − for an early review, see Faber & Gallagher (1979).”

“…to date, the HI rotation curve is the most robust indicator of the presence of dark matter in galaxies, and it is routinely used to investigate the properties of the dark matter halos (Bosma 1978, 1981; van Albada et al. 1985; Begeman 1987; de Blok et al. 2008; Oh et al. 2015; Iorio et al. 2017).”