Spiral Galaxies In Distant Clusters Research Articles

Internal kinematics of spiral galaxies in distant clusters

(Abridged) We trace the interaction processes of galaxies at intermediate redshift by measuring the irregularity of their ionized gas kinematics, and investigate these irregularities as a function of the environment (cluster versus field) and of morphological type (spiral versus irregular). Our sample consists of 92 distant galaxies. 16 cluster (z~0.3 and z~0.5) and 29 field galaxies (mean z=0.44) of these have velocity fields with sufficient signal to be analyzed. We find that the fraction of galaxies that have irregular gas kinematics is remarkably similar in galaxy clusters and in the field at intermediate redshifts. The distribution of the field and cluster galaxies in (ir)regularity parameters space is also similar. On the other hand galaxies with small central concentration of light, that we see in the field sample, are absent in the cluster sample. We find that field galaxies at intermediate redshifts have more irregular velocity fields as well as more clumpy and less centrally concentrated light distributions than their local counterparts. Comparison with a SINS sample of 11 z ~ 2 galaxies shows that these distant galaxies have more irregular gas kinematics than our intermediate redshift cluster and field sample. We do not find a dependence of the irregularities in gas kinematics on morphological type. We find that two different indicators of star formation correlate with irregularity in the gas kinematics. More irregular gas kinematics, also more clumpy and less centrally concentrated light distributions of spiral field galaxies at intermediate redshifts in comparison to their local counterparts indicate that these galaxies are probably still in the process of building their disks via mechanisms such as accretion and mergers. On the other hand, they have less irregular gas kinematics compared to galaxies at z ~ 2.

THE NATURE OF DUSTY STARBURST GALAXIES IN A RICH CLUSTER ATz= 0.4: THE PROGENITORS OF LENTICULARS?

We present the results of a Spitzer Infrared Spectrograph (IRS) survey of 24um-selected luminous infrared galaxies (LIRGs, L_IR > 10^11 L_sun) in the rich cluster Cl0024+16 at z=0.4. Optically, these LIRGs resemble unremarkable spiral galaxies with e(a)/e(c) spectral classifications and [Oii]-derived star formation rates (SFRs) of <2 M_sun/yr, generally indistinguishable from the 'quiescent' star forming population in the cluster. Our IRS spectra show that the majority of the 24um-detected galaxies exhibit polycyclic aromatic hydrocarbon (PAH) emission with implied SFRs ~30-60 M_sun/yr, with only one (<10%) of the sample displaying unambiguous evidence of an active galactic nucleus in the mid-infrared. This confirms the presence of a large population of obscured starburst galaxies in distant clusters, which comprise the bulk of the star formation occurring in these environments at z~0.5. We suggest that, although several mechanisms could be at play, these dusty starbursts could be the signature of an important evolutionary transition converting gas-rich spiral galaxies in distant clusters into the passive, bulge-dominated lenticular galaxies that become increasingly abundant in the cores of rich clusters in the ~4Gyr to the present day.

Internal kinematics of spiral galaxies in distant clusters

Internal kinematics of spiral galaxies in distant clusters

Distant Galaxy Transformation Probed by VLT and HST

AbstractWe investigate the morphologies and velocity fields of spiral galaxies in distant clusters (z ~ 0.5) focussing on signatures from interactions. Structural parameters and peculiarities are determined with HST/ACS images. To derive the internal kinematics and rotation curves we have performed 3D–spectroscopy allowing the construction of the full velocity field for each galaxy. Combining both approaches, transformation mechanisms are revealed that affect not only the stellar populations but also the mass distribution. The observations are supported by N-body/SPH simulations of different interaction processes.

The Tully—Fisher relation of distant cluster galaxies

We have measured maximum rotation velocities (Vrot) for a sample of 111 emission-line galaxies with 0.1 < z < 1, observed in the fields of 6 clusters. From these data we construct 'matched' samples of 58 field and 22 cluster galaxies, covering similar ranges in redshift (0.25 < z < 1.0) and luminosity (M_B < -19.5 mag), and selected in a homogeneous manner. We find the distributions of M_B, Vrot, and scalelength, to be very similar for the two samples. However, using the Tully-Fisher relation (TFR) we find that cluster galaxies are systematically offset with respect to the field sample by -0.7+-0.2 mag. This offset is significant at 3 sigma and persists when we account for an evolution of the field TFR with redshift. Extensive tests are performed to investigate potential differences between the measured emission lines and derived rotation curves of the cluster and field samples. However, no such differences which could affect the derived Vrot values and account for the offset are found. The most likely explanation for the TFR offset is that giant spiral galaxies in distant clusters are on average brighter, for a given rotation velocity, than those in the field. We discuss the potential mechanisms responsible for this, and consider alternative explanations.

Internal kinematics of spiral galaxies in distant clusters

We present first results from our project to examine the internal kinematics of disk galaxies in 7 rich clusters with 0.3<=z<0.6. Spatially resolved MOS spectra have been obtained with FORS at the VLT. We concentrate here on the clusters MS1008.1-1224 at z=0.30 and Cl0413-6559 (F1557.19TC) at z=0.51. Out of 22 cluster members, 12 galaxies exhibit a rotation curve of the universal form rising in the inner region and passing over into a flat part. The other members have intrinsically peculiar kinematics. The 12 cluster galaxies for which a maximum rotation velocity could be derived are distributed in the Tully-Fisher diagram very similar to field galaxies from the FORS Deep Field with corresponding redshifts. The same is true for 6 galaxies observed in the cluster fields that turned out not to be members. In particular, these cluster spirals do not show any significant luminosity evolution as might be expected from certain clusterspecific phenomena. Contrary to that, the other half of the cluster sample with disturbed kinematics also shows a higher degree of structural assymetries on average indicating ongoing or recent interaction processes.

Internal Kinematics of Spiral Galaxies in Distant Clusters

We introduce our project on galaxy evolution in the environment of rich clusters, aiming at disentangling the importance of specific interaction and galaxy transformation processes from the hierarchical evolution of galaxies in the field. Emphasis is laid on the examination of the internal kinematics of disk galaxies through spatially resolved multiobject spectroscopy with FORS at the Very Large Telescope. First results are presented for the clusters MS 1008.1-1224 (z = 0.30), Cl 0303+1706 (z = 0.42), and Cl 0413-6559 (F1557.19TC; z = 0.51). Out of 30 cluster members with emission lines, 13 galaxies exhibit a rotation curve of the universal form rising in the inner region and passing over into a flat part. The other members have either intrinsically peculiar kinematics (4), too strong geometric distortions (9), or a too low signal-to-noise ratio (4) for a reliable classification of their velocity profiles. The 13 cluster galaxies for which a maximum rotation velocity could be derived are distributed in the Tully-Fisher diagram very similar to field galaxies from the FORS Deep Field that have corresponding redshifts and do not show any significant luminosity evolution with respect to local samples. The same is true for the seven galaxies observed in the cluster fields that turned out not to be members. The mass-to-light ratios of the 13 Tully-Fisher cluster spiral galaxies cover the same range as the distant field population, indicating that their stellar populations were not dramatically changed by possible cluster-specific interaction phenomena. The cluster members with distorted kinematics may be subject to interaction processes, but it is impossible to determine whether or not these processes also lead to changes in the overall luminosity of their stellar populations.

Passive Spiral Formation from Halo Gas Starvation: Gradual Transformation into S0s

Recent spectroscopic and high-resolution Hubble Space Telescope (HST) imaging observations have revealed significant numbers of spiral galaxies in distant clusters, with all the morphological hallmarks of a spiral galaxy (in particular, spiral arm structure), but with weak or absent star formation. Exactly how such spiral galaxies formed and whether they are the progenitors of present-day S0 galaxies is unclear. Based on analytic arguments and numerical simulations of the hydrodynamical evolution of a spiral galaxy's halo gas (which is a likely candidate for the source of gas replenishment for star formation in spirals), we show that the origin of passive spirals may well be associated with halo gas stripping. Such stripping results mainly from the hydrodynamical interaction between the halo gas and the hot intracluster gas. Our numerical simulations demonstrate that even if a spiral orbits a cluster with a pericenter distance ~3 times larger than the cluster core radius, ~80% of the halo gas is stripped within a few Gyr and, accordingly, cannot be accreted by the spiral. Furthermore, our study demonstrates that this dramatic decline in the gaseous infall rate leads to a steady increase in the Q parameter for the disk, with the spiral arm structure, although persisting, becoming less pronounced as the star formation rate gradually decreases. These results suggest that passive spirals formed in this way gradually evolve into red cluster S0s.

Abell 154 and Virgo - Pilot study for H I observations of distant clusters of galaxies

As a test of procedures required to study the H I contents of spiral galaxies in distant clusters of galaxies, the cluster Abell 154 has been observed from Arecibo. Fourteen candidate detections were found in two regions of the cluster comprising about 10 percent of the cluster area. These results are compared in detail with those expected for the exhaustively studied Virgo cluster displaced to the distance of A 154. Most of the candidate detections are likely to be the combined profiles of two or more spiral galaxies, many of them too faint to appear on the list of morphological types classified by Dressler (1980). Any attempt to identify these H I signals with known bright spirals is problematic at best. The A 154 profiles are systematically broader than expected for Virgo, but a crude application of the Tully-Fisher correlation indicates that they are still consistent with available photometric data. While the H I deficiency in Virgo would still be apparent at the A 154 distance, no significant evidence is found for H I deficiency in A 154. 46 refs.