Hα Kinematics Research Articles

Spatially resolved Hα and ionizing photon production efficiency in the lensed galaxy MACS1149-JD1 at a redshift of 9.11

We present MIRI/JWST medium-resolution spectroscopy (MRS) and imaging (MIRIM) of the lensed galaxy MACS1149-JD1 at a redshift of z = 9.1092 ± 0.0002, when the Universe was about 530 Myr old. We detect, for the first time, spatially resolved Hα emission in a galaxy at a redshift above nine. The structure of the Hα emitting gas consists of two clumps, S and N, carrying about 60% and 40% of the total flux, respectively. The total Hα luminosity implies an instantaneous star-formation rate in the range of 3.2 ± 0.3 and 5.3 ± 0.4 M⊙ yr−1 for sub-solar and solar metallicities. The ionizing photon production efficiency, log(ζion), shows a spatially resolved structure with values of 25.55 ± 0.03; 25.47 ± 0.03; and 25.91 ± 0.09 Hz erg−1 for the integrated galaxy and clumps S and N, respectively. The Hα rest-frame equivalent width, EW0 (Hα), is 726−182+660 Å for the integrated galaxy, but it presents extreme values of 531−96+300 Å and ≥1951 Å for clumps S and N, respectively. The spatially resolved ionizing photon production efficiency is within the range of values measured in galaxies at a redshift above six and well above the canonical value (25.2 ± 0.1 Hz erg−1). The EW0 (Hα) is a factor of two lower than the predicted value at z = 9.11 based on the extrapolation of the evolution of the EW0 (Hα) with redshifts, ∝(1 + z)2.1, including galaxies detected with JWST. The extreme difference of the EW0 (Hα) for clumps S and N indicates the presence of a recent (< 5 Myr) stellar burst in clump N and a star formation over a larger period of time (e.g., ∼50 Myr) in clump S. The different ages of the stellar population place MACS1149-JD1 and clumps N and S at different locations in the log(ζion) to EW0 (Hα) plane and above the main relation defined from intermediate- and high-redshift (z = 3 − 7) galaxies detected with JWST. Finally, clump S and N show very different Hα kinematics, with velocity dispersions of 56 ± 4 km s−1 and 113 ± 33 km s−1, likely indicating the presence of outflows or increased turbulence in clump N. The dynamical mass Mdyn = (2.4 ± 0.5) × 109 M⊙, obtained from the size of the integrated Hα ionized nebulae and its velocity dispersion, is within the range previously measured with the spatially resolved [OIII]88 μm line.

Galaxy kinematics and mass estimates at z ∼ 1 from ionized gas and stars

ABSTRACT We compare ionized gas and stellar kinematics of 16 star-forming galaxies (log (M⋆/M⊙) = 9.7–11.2, SFR =6 − 86 M⊙ yr−1) at z ∼ 1 using near-infrared integral field spectroscopy (IFS) of Hα emission from the KMOS3D (the K-band Multi-Object Spectrograph 3D) survey and optical slit spectroscopy of stellar absorption and gas emission from the LEGA-C (Large Early Galaxy Astrophysics Census) survey. Hα is dynamically colder than stars, with higher disc rotation velocities (by ∼45 per cent) and lower disc velocity dispersions (by a factor ∼2). This is similar to trends observed in the local Universe. We find higher rotational support for Hα relative to [O ii], potentially explaining systematic offsets in kinematic scaling relations found in the literature. Regarding dynamical mass measurements, for six galaxies with cumulative mass profiles from Jeans Anisotropic Multi-Gaussian Expansion (JAM) models the Hα dynamical mass models agree remarkably well out to ∼10 kpc for all but one galaxy (average $\Delta M_{\rm dyn}(R_{e,\rm F814W})\lt 0.1$ dex). Simpler dynamical mass estimates based on integrated stellar velocity dispersion are less accurate (standard deviation 0.24 dex). Differences in dynamical mass estimates are larger, for example, for galaxies with stronger misalignments of the Hα kinematic major axis and the photometric position angle, highlighting the added value of IFS observations for dynamics studies. The good agreement between the JAM and the dynamical models based on Hα kinematics at z ∼ 1 corroborates the validity of dynamical mass measurements from Hα IFS observations, which can be more easily obtained for higher redshift galaxies.

Hα kinematics of superbubbles and supernova remnants of the dwarf galaxy NGC 4214

ABSTRACT We analysed the ionized gas kinematics of the dwarf galaxy NGC 4214 using high resolution Fabry–Perot interferometry observations and present a set of narrowband images in the Hα, [S ii] λ6717 Å, [N ii] λ6584 Å, and [O iii] λ5007 Å emission lines. The high-resolution Fabry–Perot observations of the Hα emission line, allowed us to derive the velocity field, the velocity dispersion σ, and the rotation curve of the galaxy. We also present for the first time, 3D kinematic maps of the complexes NGC 4214-I and NGC 4214-II and analysed the kinematics of the ionized gas of two new superbubbles, as well as the supernova remnants previously detected in this galaxy by other authors, in radio, optical, and X-ray emission. We computed the expansion velocities of the superbubbles and supernova remnants fitting their velocity profiles and obtained their respective physical parameters. We found that the superbubbles have an expansion velocity of ∼50 km s −1, dynamical age about ∼2 Myr and wind luminosity LW of ∼9 × 1038 erg s−1 produced probably by massive stars in OB associations. For supernova remnants, their expansion velocities are between ∼48 and ∼80 km s−1 with ages of about 104 yr and kinetic energy of about 1051 erg assuming they are in the radiative phase of evolution.

An ∼600 pc View of the Strongly Lensed, Massive Main-sequence Galaxy J0901: A Baryon-dominated, Thick Turbulent Rotating Disk with a Clumpy Cold Gas Ring at z = 2.259

We present a high-resolution kinematic study of the massive main-sequence star-forming galaxy (SFG) SDSS J090122.37+181432.3 (J0901) at z = 2.259, using ∼0.″36 Atacama Large Millimeter/submillimeter Array CO(3–2) and ∼0.″1–0.″5 SINFONI/VLT Hα observations. J0901 is a rare, strongly lensed but otherwise normal massive () main-sequence SFG, offering a unique opportunity to study a typical massive SFG under the microscope of lensing. Through forward dynamical modeling incorporating lensing deflection, we fit the CO and Hα kinematics in the image plane out to about one disk effective radius (R e ∼ 4 kpc) at an ∼600 pc delensed physical resolution along the kinematic major axis. Our results show high intrinsic dispersions of the cold molecular and warm ionized gas (σ 0,mol. ∼ 40 km s−1 and σ 0,ion. ∼ 66 km s−1) that remain constant out to R e; a moderately low dark matter fraction (f DM ∼ 0.3–0.4) within R e; and a centrally peaked Toomre Q parameter—agreeing well with the previously established σ 0 versus z, f DM versus Σbaryon, and Q's radial trends using large-sample non-lensed main-sequence SFGs. Our data further reveal a high stellar mass concentration within ∼1–2 kpc with little molecular gas, and a clumpy molecular gas ring-like structure at R ∼ 2–4 kpc, in line with the inside-out quenching scenario. Our further analysis indicates that J0901 had assembled half of its stellar mass only ∼400 Myr before its observed cosmic time, and the cold gas ring and dense central stellar component are consistent with signposts of a recent wet compaction event of a highly turbulent disk found in recent simulations.

The ALMaQUEST Survey. VIII. What Causes the Discrepancy in the Velocity between the CO and Hα Rotation Curves in Galaxies?

We compare the CO(1–0) and Hα kinematics in 34 nearby galaxies, selected from the ALMaQUEST and EDGE-CALIFA surveys. We use 3D-Barolo, a 3D tilted-ring model, to derive the CO and Hα rotation curves. Before comparing rotation curves in the 34 nearby galaxies, we found systematics between the MaNGA and CALIFA data using eight MaNGA-CALIFA overlapping galaxies. We assume the rotation curves based on the MaNGA data are accurate and made the corresponding correction to the CALIFA data. Our result shows that ∼56% (19/34) of our galaxies present slower Hα rotation curves compared to the CO rotation curves, with a median value of 6.5 km s−1. The remaining galaxies (15/34) show consistent CO–Hα rotation velocity within uncertainties. As a result, the Hα rotation may underestimate the total dynamical mass by 6% for a circular velocity of 200 km s−1 (the median value in our sample). Furthermore, the difference in the velocity between the CO and Hα rotational velocity is found to correlate with the difference in velocity dispersion between CO and Hα, suggesting that gas pressure plays a role in the discrepancy in velocity. After incorporating the effect of pressure support due to the turbulent gas motion into our sample, the median value of the difference in the velocities decreases to 1.9 km s−1, which in turn reduces the underestimation of the dynamical mass to ∼2%. Finally, we also investigate the role that the extraplanar diffuse ionized gas plays in the discrepancy in the velocity of CO–Hα.

The Triangulum Extended (TREX) Survey: The Stellar Disk Dynamics of M33 as a Function of Stellar Age

Abstract Triangulum (M33) is a low-mass, relatively undisturbed spiral galaxy that offers a new regime in which to test models of dynamical heating. In spite of its proximity, M33's dynamical heating history has not yet been well-constrained. In this work, we present the TREX Survey, the largest stellar spectroscopic survey across the disk of M33. We present the stellar disk kinematics as a function of age to study the past and ongoing dynamical heating of M33. We measure line-of-sight velocities for ∼4500 disk stars. Using a subset, we divide the stars into broad age bins using Hubble Space Telescope and Canada–France–Hawaii Telescope photometric catalogs: massive main-sequence stars and helium-burning stars (∼80 Myr), intermediate-mass asymptotic branch stars (∼1 Gyr), and low-mass red giant branch stars (∼4 Gyr). We compare the stellar disk dynamics to that of the gas using existing H i, CO, and Hα kinematics. We find that the disk of M33 has relatively low-velocity dispersion (∼16 km s−1), and unlike in the Milky Way and Andromeda galaxies, there is no strong trend in velocity dispersion as a function of stellar age. The youngest disk stars are as dynamically hot as the oldest disk stars and are dynamically hotter than predicted by most M33-like low-mass simulated analogs in Illustris. The velocity dispersion of the young stars is highly structured, with the large velocity dispersion fairly localized. The cause of this high-velocity dispersion is not evident from the observations and simulated analogs presented here.

Morphologies of Wolf–Rayet Planetary Nebulae Based on IFU Observations

Integral field unit (IFU) spectroscopy of planetary nebulae (PNe) provides a plethora of information about their morphologies and ionization structures. An IFU survey of a sample of PNe around hydrogen-deficient stars has been conducted with the Wide Field Spectrograph (WiFeS) on the ANU 2.3-m telescope. In this paper, we present the Hα kinematic observations of the PN M 2-42 with a weak emission-line star (wels), and the compact PNe Hen 3-1333 and Hen 2-113 around Wolf–Rayet ([WR]) stars from this WiFeS survey. We see that the ring and point-symmetric knots previously identified in the velocity [N ii] channels of M 2-42 are also surrounded by a thin exterior ionized Hα halo, whose polar expansion is apparently faster than the low-ionization knots. The velocity-resolved Hα channel maps of Hen 3-1333 and Hen 2-113 also suggest that the faint multipolar lobes may get to a projected outflow velocity of ∼100 ± 20 km s−1 far from the central stars. Our recent kinematic studies of the WiFeS/IFU survey of other PNe around [WR] and wels mostly hint at elliptical morphologies, while collimated outflows are present in many of them. As the WiFeS does not have adequate resolution for compact (≤6 arcsec) PNe, future high-resolution spatially-resolved observations are necessary to unveil full details of their morpho-kinematic structures.

The multifarious ionization sources and disturbed kinematics of extraplanar gas in five low-mass galaxies

Aims.We investigate the origin of the extraplanar diffuse ionized gas (eDIG) and its predominant ionization mechanisms in five nearby (17–46 Mpc) low-mass (109–1010M⊙) edge-on disk galaxies: ESO 157-49, ESO 469-15, ESO 544-27, IC 217, and IC 1553.Methods.We acquired Multi Unit Spectroscopic Explorer (MUSE) integral field spectroscopy and deep narrowband Hαimaging of our sample galaxies. To investigate the connection between in-plane star formation and eDIG, we measure the star formation rates (SFRs) and perform a photometric analysis of our narrowband Hαimaging. Using our MUSE data, we investigate the origin of eDIG via kinematics, specifically the rotation velocity lags. We also construct standard diagnostic diagrams and emission-line maps (EW(Hα), [N II]/Hα, [S II]//Hα, [O III]/Hβ) and search for regions consistent with ionization by hot low-mass evolved stars (HOLMES) and shocks.Results.We measure eDIG scale heights ofhzeDIG = 0.59−1.39 kpc and find a positive correlation between them and specific SFRs. In all galaxies, we also find a strong correlation between extraplanar and midplane radial Hαprofiles. These correlations along with diagnostic diagrams suggest that OB stars are the primary driver of eDIG ionization. However, we find regions consistent with mixed OB–HOLMES and OB–shock ionization in all galaxies and conclude that both HOLMES and shocks may locally contribute to the ionization of eDIG to a significant degree. From Hαkinematics, we find rotation velocity lags above the midplane with values between 10 and 27 km s−1kpc−1. While we do find hints of an accretion origin for the ionized gas in ESO 157–49, IC 217, and IC 1553, overall the ionized gas kinematics of our galaxies do not match a steady galaxy model or any simplistic model of accretion or internal origin for the gas.Conclusions.Despite our galaxies’ similar structures and masses, our results support a surprisingly composite image of ionization mechanisms and a multifarious origin for the eDIG. Given this diversity, a complete understanding of eDIG will require larger samples and composite models that take many different ionization and formation mechanisms into account.

Observations of cold gas and star formation in dwarf S0 galaxies

ABSTRACT Very little work has been done on star formation in dwarf lenticular galaxies (S0s). We present 2D spectroscopic and millimetre observations made by the Centro Astronómico Hispano Alemán (CAHA) 3.5-m optical and Institut de Radioastronomie Millimétrique (IRAM) 30-m millimetre telescopes, respectively, for a sample of four dwarf S0 galaxies with multiple star formation regions in the field environment. We find that, although most of the sources deviate from the star-forming main-sequence relation, they all follow the Kennicutt–Schmidt law. After comparing the stellar and Hα kinematics, we find that the velocity fields of both stars and ionized gas show no regular motion and the velocity dispersions of both stars and ionized gas are low in regions with high star formation, suggesting that these star-forming S0 galaxies still have significant rotation. This view can be supported by the result that most of these dwarf S0 galaxies are classified as fast rotators. The ratio of the average atomic gas mass to stellar mass ($\sim 47{{\ \rm per\ cent}}$) is much greater than that of the molecular gas mass to stellar mass ($\sim 1{{\ \rm per\ cent}}$). In addition, gas-phase metallicities in star-forming regions are lower than those of non-star-forming regions. These results indicate that extended star formation may originate from the combination of abundant atomic hydrogen, a long dynamic time-scale, and a low-density environment.

The EDGE-CALIFA Survey: Evidence for Pervasive Extraplanar Diffuse Ionized Gas in Nearby Edge-on Galaxies

Abstract We investigate the prevalence, properties, and kinematics of extraplanar diffuse ionized gas (eDIG) in a sample of 25 edge-on galaxies selected from the CALIFA survey. We measure ionized gas scale heights from Hα and find that 90% have measurable scale heights with a median of kpc. From the Hα kinematics, we find that 60% of galaxies show a decrease in the rotation velocity as a function of height above the midplane. This lag is characteristic of eDIG, and we measure a median lag of 21 km s−1 kpc−1, which is comparable to lags measured in the literature. We also investigate variations in the lag with radius. H i lags have been reported to systematically decrease with galactocentric radius. We find both increasing and decreasing ionized gas lags with radius, as well as a large number of galaxies consistent with no radial lag variation, and investigate these results in the context of internal and external origins for the lagging ionized gas. We confirm that the [S ii]/Hα and [N ii]/Hα line ratios increase with height above the midplane as is characteristic of eDIG. The ionization of the eDIG is dominated by star-forming complexes (leaky H ii regions). We conclude that the lagging ionized gas is turbulent ejected gas likely resulting from star formation activity in the disk as opposed to gas in the stellar thick disk or bulge. This is further evidence for the eDIG being a product of stellar feedback and for the pervasiveness of this WIM-like phase in many local star-forming galaxies.

KMOS3D Reveals Low-level Star Formation Activity in Massive Quiescent Galaxies at 0.7 < z < 2.7∗

Abstract We explore the Hα emission in the massive quiescent galaxies observed by the KMOS3D survey at 0.7 < z < 2.7. The Hα line is robustly detected in 20 out of 120 UVJ-selected quiescent galaxies, and we classify the emission mechanism using the Hα line width and the [N ii]/Hα line ratio. We find that AGNs are likely to be responsible for the line emission in more than half of the cases. We also find robust evidence for star formation activity in nine quiescent galaxies, which we explore in detail. The Hα kinematics reveal rotating disks in five of the nine galaxies. The dust-corrected Hα star formation rates are low (0.2–7 M ⊙ yr−1), and place these systems significantly below the main sequence. The 24 μm-based, infrared luminosities, instead, overestimate the star formation rates. These galaxies present a lower gas-phase metallicity compared to star-forming objects with similar stellar mass, and many of them have close companions. We therefore conclude that the low-level star formation activity in these nine quiescent galaxies is likely to be fueled by inflowing gas or minor mergers, and could be a sign of rejuvenation events.

THE ANGULAR MOMENTUM DISTRIBUTION AND BARYON CONTENT OF STAR-FORMING GALAXIES AT z ∼ 1–3*

ABSTRACT We analyze the angular momenta of massive star-forming galaxies (SFGs) at the peak of the cosmic star formation epoch (z ∼ 0.8–2.6). Our sample of ∼360 log(M */M ⊙) ∼ 9.3–11.8 SFGs is mainly based on the KMOS3D and SINS/zC-SINF surveys of Hα kinematics, and collectively provides a representative subset of the massive star-forming population. The inferred halo scale angular momentum distribution is broadly consistent with that theoretically predicted for their dark matter halos, in terms of mean spin parameter ∼ 0.037 and its dispersion (σ logλ ∼ 0.2). Spin parameters correlate with the disk radial scale and with their stellar surface density, but do not depend significantly on halo mass, stellar mass, or redshift. Our data thus support the long-standing assumption that on average, even at high redshifts, the specific angular momentum of disk galaxies reflects that of their dark matter halos (j d = j DM). The lack of correlation between λ × (j d /j DM) and the nuclear stellar density Σ*(1 kpc) favors a scenario where disk-internal angular momentum redistribution leads to “compaction” inside massive high-redshift disks. For our sample, the inferred average stellar to dark matter mass ratio is ∼2%, consistent with abundance matching results. Including the molecular gas, the total baryonic disk to dark matter mass ratio is ∼5% for halos near 1012 M ⊙, which corresponds to 31% of the cosmologically available baryons, implying that high-redshift disks are strongly baryon dominated.

Hα kinematics of nearby galaxies using Fabry-Perot and IFU data

AbstractI present here analysis of the shapes of the rotation curves of a large sample of nearby spiral galaxies with high angular and spectral resolution Hα (Fabry-Perot GHαFaS) kinematics, and the resulting constraints on their total mass distributions. In particular I discuss how their rotation curve shapes relate to key galaxy properties. Finally I present related results from the MUSE Atlas of Disks (MAD) program, which is dissecting the nearby disk population with IFU spectroscopy at ~100pc resolution.

GHASP: an Hα kinematic survey of spiral galaxies – X. Surface photometry, decompositions and the Tully–Fisher relation in theRcband

We present Rc-band surface photometry for 170 of the 203 galaxies in GHASP, Gassendi H-Alpha survey of SPirals, a sample of late-type galaxies for which high-resolution Fabry-Perot H{\alpha} maps have previously been obtained. Our data set is constructed by new Rc-band observations taken at the Observatoire de Haute-Provence (OHP), supplemented with Sloan Digital Sky Survey (SDSS) archival data, obtained with the purpose of deriving homogeneous photometric profiles and parameters. Our results include Rc-band surface brightness profiles for 170 galaxies and $ugriz$ profiles for 108 of these objects. We catalogue several parameters of general interest for further reference, such as total magnitude, effective radius and isophotal parameters -- magnitude, position angle, ellipticity and inclination. We also perform a structural decomposition of the surface brightness profiles using a multi-component method in order to separate disks from bulges and bars, and to observe the main scaling relations involving luminosities, sizes and maximum velocities. We determine the Rc-band Tully Fisher relation using maximum velocities derived solely from H$\alpha$ rotation curves for a sample of 80 galaxies, resulting in a slope of $-8.1 \pm 0.5$, zero point of $-3.0 \pm 1.0$ and an estimated intrinsic scatter of $0.28 \pm 0.07$. We note that, different from the TF-relation in the near-infrared derived for the same sample, no change in the slope of the relation is seen at the low-mass end (for galaxies with $V_{max} < 125$ km/s). We suggest that this different behaviour of the Tully Fisher relation (with the optical relation being described by a single power-law while the near-infrared by two) may be caused by differences in the stellar mass to light ratio for galaxies with $V_{max} < 125$ km/s.

DYNAMO Survey: An Upclose View of Clumpy Galaxies

AbstractWe highlight recent results on the DYNAMO survey of turbulent, clumpy disks galaxies found at z=0.1. Bright star forming DYNAMO galaxies are found to be very similar in properties to star forming galaxies in the high redshift Universe. Typical star formation rates of turbulent DYNAMO galaxies range 10-80 M⊙ yr−1. Roughly 2/3 of DYNAMO galaxies have Hα kinematics that are consistent with rotation. The typical gas velocity dispersion of DYNAMO galaxies is σHα ~ 20 - 60 km s−1. We show that, when convolved to the same resolution, maps of Hα emission in DYNAMO galaxies have essentially identical morphology as that of z ~ 1 - 3 galaxies. Finally, DYNAMO galaxies have high molecular gas fractions fmol ~ 20 - 35%. We note that DYNAMO galaxies are not dwarfs, typical masses are Mstar ~ 0.8 - 8 × 1010 M⊙. These data are all consistent with a scenario in which despite being at relatively low redshift the DYNAMO galaxies are forming stars similarly to that observed in the high-redshift Universe, that is to say star formation is occurring in very massive (Mclump ~ 109 M⊙), very large (rclump ~ 300 pc) clumps of gas.

The Hα kinematics of interacting galaxies in 12 compact groups★

We present new Fabry-Perot observations for a sample of 42 galaxies located in twelve compact groups of galaxies: HCG 1, HCG 14, HCG 25, HCG 44, HCG 53, HCG 57, HCG 61, HCG 69, HCG 93, VV 304, LGG 455 and Arp 314. From the 42 observed galaxies, a total of 26 objects are spiral galaxies, which range from Sa to Im morphological types. The remaining 16 objects are E, S0 and S0a galaxies. Using these observations, we have derived velocity maps, monochromatic and velocity dispersion maps for 24 galaxies, where 18 are spiral, three are S0a, two are S0 and one is an Im galaxy. From the 24 velocity fields obtained, we could derive rotation curves for 15 galaxies; only two of them exhibit rotation curves without any clear signature of interactions. Based on kinematic information, we have evaluated the evolutionary stage of the different groups of the current sample. We identify groups that range from having no H$\alpha$ emission to displaying an extremely complex kinematics, where their members display strongly perturbed velocity fields and rotation curves. In the case of galaxies with no H$\alpha$ emission, we suggest that past galaxy interactions removed their gaseous components, thereby quenching their star formation. However, we can not discard that the lack of H$\alpha$ emission is linked with the detection limit for some of our observations.

Spatially resolved kinematics of the multi-phase interstellar medium in the inner disc of M82

We present spatially resolved kinematics of the interstellar Na i D λλ5890,5896 doublet absorption and CO (1→0) emission across the inner ∼2× 1 kpc of the disk of M82. These data were obtained with the DensePak IFU on the WIYN telescope and the Caltech Owens Valley Radio Observatory (OVRO) millimetre array. By measuring the Na i and CO (and Hα kinematics from a previous study) at the same spatial resolution, and employing the same line fitting method, we have been able to make meaningful comparisons between the ionized, neutral and molecular gas phases. We detect a component of the Na i line throughout the inner disk with velocities that are forbidden by the known galactic rotation. We interpret this as originating in counterrotating or perhaps inflowing material. In the southern plume, we find clear evidence of entrained CO gas with kinematics consistent with that of Hα. On the northern side, the CO kinematics appear to trace more static clouds in the inner halo that could be pre-existing or tidal in origin. We find no evidence that Na i absorption is kinematically associated with the outflow. We conclude that a combination of lack of velocity resolution and confusion of due to the high inclination of the system is acting to prevent detection. Thus, in the search for neutral outflows from galaxies, the signature high velocity components may easily be missed in observations at low spectral resolution and/or sensitivity, and particularly so in highly inclined systems.

The M 82 superwind – in detail, and in 3D

It has long been known that the starburst in M 82 drives a large-scale bipolar superwind, carrying large volumes of material (in the form of hot, warm and cool gas and dust) out of the disk plane. However, what is not known is exactly how the hundreds of catalogued super star clusters power the outflow, and how it becomes so structured and collimated. Here I will present part of the most comprehensive set of spectroscopic integral field observations ever made of the starburst clumps and outflow in M 82. I will describe how we have mapped in detail the spatial variation of Hα kinematics, gas density and excitation from the wind roots out into the halo, and how these compare to features seen in recent high resolution imaging campaigns. These observations will be used to address questions such as: how does the 2D variation of gas kinematics evolve from the core out into the halo? Our spectra indicate evidence for the sites of mass-loading – where is it occurring within the wind?

GHASP: an Hα kinematic survey of spiral and irregular galaxies - IX. The near-infrared, stellar and baryonic Tully-Fisher relations★

We studied, for the first time, the near infrared, stellar and baryonic Tully-Fisher relations for a sample of field galaxies taken from an homogeneous Fabry-Perot sample of galaxies (the GHASP survey). The main advantage of GHASP over other samples is that maximum rotational velocities were estimated from 2D velocity fields, avoiding assumptions about the inclination and position angle of the galaxies. By combining these data with 2MASS photometry, optical colors, HI masses and different mass-to-light ratio estimators, we found a slope of 4.48\pm0.38 and 3.64\pm0.28 for the stellar and baryonic Tully-Fisher relation, respectively. We found that these values do not change significantly when different mass-to-light ratios recipes were used. We also point out, for the first time, that rising rotation curves as well as asymmetric rotation curves show a larger dispersion in the Tully-Fisher relation than flat ones or than symmetric ones. Using the baryonic mass and the optical radius of galaxies, we found that the surface baryonic mass density is almost constant for all the galaxies of this sample. In this study we also emphasize the presence of a break in the NIR Tully-Fisher relation at M(H,K)\sim-20 and we confirm that late-type galaxies present higher total-to-baryonic mass ratios than early-type spirals, suggesting that supernova feedback is actually an important issue in late-type spirals. Due to the well defined sample selection criteria and the homogeneity of the data analysis, the Tully-Fisher relation for GHASP galaxies can be used as a reference for the study of this relation in other environments and at higher redshifts.

Two-dimensional Hα kinematics of bulgeless disc galaxies

We present two-dimensional H_alpha velocity fields for 20 late-type, disk-dominated spiral galaxies, the largest sample to date with high-resolution H_alpha velocity fields for bulgeless disks. From these data we derive rotation curves and the location of the kinematic centers. The galaxy sample was selected to contain nucleated and non-nucleated galaxies, which allows us to investigate what impact the gas kinematics in the host disk have on the presence (or absence) of a nuclear star cluster. In general, we find that the velocity fields span a broad range of morphologies. While some galaxies show regular rotation, most have some degree of irregular gas motions. There appears to be no systematic difference in the kinematics of nucleated and non-nucleated disks. Due to the large fields of view of the integral field units we use, we are able to observe the flattening of the rotation curve in almost all of our sample galaxies. This makes modeling of the velocity fields relatively straight-forward. Due to the complexities of the velocity fields, we obtain reliable determinations of the kinematic center for only 6 of our 20 sample galaxies. For all of these the locations of the nuclear star cluster/photometric center and the kinematic center agree within the uncertainties. If we disregard all kinematically irregular galaxies, our study concludes that nuclear star clusters truly occupy the nuclei, or dynamical centers, of their hosts. Our results are thus consistent with in-situ formation of nuclear star clusters. Yet, many well-motivated formation scenarios for nuclear clusters invoke off-center cluster formation and subsequent sinking of clusters due to dynamical friction. In that case, our results imply that dynamical friction in the centers of bulgeless galaxies must be very effective in driving massive clusters to the kinematic center. (abridged)