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# Globular Clusters in Virgo Ellipticals: Unexpected Results for Giants, Dwarfs, and Nuclei from ACS Imaging
Jay Strader, Jean P. Brodie, Lee Spitler, Michael A. Beasley
UCO/Lick Observatory, University of California, Santa Cruz, CA 95064 strader@ucolick.org, brodie@ucolick.org, lees@ucolick.org, mbeasley@ucolick.org... | [] | |
function (GCLF) is the same for both gEs and dEs. This is contrary to expectations of dynamical friction on massive GCs, unless the primordial GCLF varies between gEs and dEs. Among gEs the GCLF turnover varies by a surprising small 0.05 mag, an encouraging result for its use as an accurate standard candle. (viii) dE,N... | [] | |
the GC systems of nucleated and non-nucleated dEs (dE,N and dE,noN, respectively), and the difficulty of making dE nuclei as observed through dynamical friction of GCs (Miller _et al._ 1998, Lotz _et al._ 2001).
Data from the Advanced Camera for Surveys (ACS) Virgo Cluster Survey (HST GO 9401, P. I. Cote) offers an im... | [] | |
in \(z\). These are median corrections derived from bright objects in the five most luminous galaxies in the Virgo Cluster Survey: VCC 1226, VCC 1316, VCC 1978, VCC 881, and VCC 798. These 10-pixel magnitudes were then corrected to a nominal infinite aperture using values of \(-0.10\) in \(g\) and \(-0.12\) in \(z\) (S... | [] | |
background sources at \(z\gtrsim 23\), combined with the difficulty of accurate size measurements below this magnitude, makes efficient rejection of contaminants challenging. For gEs this is a minimal problem, due to the large number of GCs within the ACS field of view (hundreds to \(\sim 1700\) for M87). But with dEs ... | [] | |
low metallicities. We fit a quadratic relation for [M/H] and \(g-z\) using Maraston (2005) model predictions for \(g-z\) for four metallicities (\(-2.25,-1.35,-0.33,0\)) and Bruzual & Charlot (2003) predictions at five metallicities (\(-2.3,-1.7,-0.7,-0.4,0\)). Both sets of models assume a 13 Gyr stellar population and... | [] | |
clusters this is difficult to constrain. Some of these luminous GCs are likely in the tail of the normal blue and red subpopulations, but given the wide range in colors (including many with intermediate colors), small galactocentric radii, and the larger-than-average sizes, a portion may also be the stripped nuclei of ... | [] | |
Interpretations of this surprising finding are discussed below; first we consider whether a bias in observation or analysis might be the cause.
Given that the correlation extends over a large range in GC luminosity, and is not seen for red GCs, selection bias (choosing redder GCs at bright magnitudes and bluer GCs at ... | [] | |
detail requires additional simulation. Any such model need also be compared to the rather stringent set of other observations of blue GCs (some of which are not usually considered), including the lack of GC mass-radius and metallicity-galactocentric radius relations and the presence of a _global_ correlation between th... | [] | |
galaxies. Nevertheless, Figure 7 shows that clear linear relationships are present for both the blue and red GCs over the full \(\sim 6-7\) mag range in parent galaxy luminosity. These weighted relations are \(g-z=-0.014\,M_{B}+0.642\) and \(g-z=-0.053\,M_{B}+0.225\) for the blue and red GCs, respectively. The plotted ... | [] | |
least some of the dEs in our sample could imply either that their formation mechanisms were more similar than expected or that red GCs are formed by a self-regulating, local process that can occur in a variety of contexts.
The mixture modeling also returns the number of GCs in each subpopulation. In Figure 8 we plot t... | [] | |
have additional scatter because of the range of galaxy distances; we find below that this appears to be quite a small effect. The individual GC systems of dEs are quite concentrated: most GCs are within \(30-40\arcsec\), beyond which the background contamination rises sharply (size measurements are unreliable at these ... | [] | |
Unfortunately, we cannot directly fit the composite dE GCLF as for the gEs--it is far too contaminated. Instead, we must first correct for background objects. As noted above, the GC systems of the dEs are very centrally concentrated. Thus we can use the outer regions of the dE images as a fiducial background. We define... | [] | |
dynamical friction was inconsistent with observations, since the observed nuclei were fainter than predicted by their simulations. They argued that some additional process was needed to oppose dynamical friction (e.g., tidal torques).
At first glance, this is supported by Figure 9--for galaxies in the luminosity range... | [] | |
GCLF was often ill-defined, with falling completeness and rising contamination. In addition, for a typical log-normal GCLF centered at \(M_{V}=-7.4\sim 3\times 10^{5}M_{\odot}\), 90% or more of the total GC system mass is in the bright half of the LF.
Many of the dEs in this study have tens or fewer detected GCs, maki... | [] | |
errors. We note again that background contamination remains as a systematic uncertainty for total GC populations.
It is tempting to argue that these groups represent different formation channels for dEs, e.g., the fading/quenching of dIrrs, harassment of low-mass spirals, or simply a continuation of the E sequence to ... | [] | |
UCO/Lick Observatory, University of California, Santa Cruz, CA 95064 strader@ucolick.org, brodie@ucolick.org, lees@ucolick.org, mbeasley@ucolick.org
###### Abstract
We have analyzed archival _Hubble Space Telescope_/Advanced Camera for Surveys images in \(g\) and \(z\) of the globular cluster (GC) systems of 53 ellip... | [
{
"caption": "Fig. 5.— g − z histograms for GCs in the ranges 22.2 < z < 22.7 (“H” GCs) and 22.8 < z < 23.3, just below. The lower panel shows the normal gap between the blue and red GC subpopulations, while the upper panel shows how the “H” GCs have filled the gap in.",
"captionBoundary": {
"x1": 96,... | |
# Keck/HIRES Spectroscopy of Four Candidate Solar Twins
Jeremy R. King
Department of Physics and Astronomy, 118 Kinard Laboratory,
Clemson University, Clemson, SC 29634-0978 jking2@ces.clemson.edu
Ann M. Boesgaard1
Footnote 1: affiliation: Visiting Astronomer, W.M. Keck Observatory, jointly operated by the Califor... | [] | |
metallicity is 0.1 dex higher than the most recent estimate of this group's metallicity. While certainly "solar-type" stars, HIP 76114 and 77718 are a few percent less massive, significantly older, and metal-poor compared to the Sun; they are neither good solar twin candidates nor solar analogs providing a look at the ... | [] | |
the evolution of planets and life surrounding solar-type stars. For example, it has been suggested that solar-type stars may be subject to highly energetic superflare outbursts, perhaps induced by orbiting planets, that would have dramatic effects on atmospheres surrounding and lifeforms inhabiting orbiting planets (Ru... | [] | |
Data and Analysis
### Observations and Reductions
Our 4 solar twin candidates were observed on UT July 8 2004 using the Keck I 10-m, its HIRES echelle spectrograph, and a Tektronix \(2048{\times}2048\) CCD detector. The chosen slit width and cross-disperser setting yielded spectra from 4475 to 6900 A at a resolution ... | [] | |
sis) and the lower excitation potential and reduced equivalent width, respectively. This approach leads to unique solutions when there is no underlying correlation between excitation potential and reduced equivalent width. We show in Figure 1 that there is no such underlying correlation in our Fe I sample. Figure 2 dis... | [] | |
quadrature to yield the total uncertainties associated with the [O/H] values given in Table 4.
### Lithium Abundances
Li abundances were derived from the \({\lambda}6707\) Li I resonance features via spectrum synthesis. Utilizing the derived parameters, synthetic spectra of varying Li abundance were created in MOOG u... | [] | |
mates (\({\sigma}{\sim}0.04\) dex) has a negligible effect on the uncertainty of our estimated masses, but would contribute an additional 0.4 Gyr uncertainty in the age estimates. The HR diagrams containing our objects and these isochrones are shown in Figure 5. +
Footnote †: margin: Fig. 5
## 3 Results and Discussio... | [] | |
spectra in the 6880 A region revealed a 9.9 km/s offset between the spectra. While larger than anticipated, this intra-night drift was confirmed by comparison of telluric water vapor features in the 6300 A region. Accounting for this drift and the appropriate relative heliocentric corrections, we find a radial velocity... | [] | |
### Solar Twin Status Evaluation
_HIP 71813_. The \(T_{\rm eff}\) value, light metal-abundances, and chromospheric Ca II emission of HIP 71813 are indistinguishable from solar values. The Li abundance, however, appears to be depleted by a factor of \({\geq}2\) compared to the Sun. More importantly, however, the star a... | [] | |
, 2005; Allende Prieto et al., 2004; Gray et al., 2003; Porto De Mello & Da Silva, 1997). \(T_{\rm eff}\) estimates range from 5693 to 5835 K, and [Fe/H] estimates from -0.06 to +0.05; the precision \(T_{\rm eff}\) analysis using line ratios (Gray, 1995) indicates a \(T_{\rm eff}\) difference with respect to the Sun of... | [] | |
\(T_{\rm eff}\) estimate of Gray (1995).
At the same time, our light metal-abundances are in excellent agreement with the photometric metallicity estimates for the 3 of our objects in Nordstrom et al. (2004), differing by no more than a few hundredths of a dex. There is no sign of the abnormally low photometric metall... | [] | |
# Initial Populations of Black Holes in Star Clusters
Krzysztof Belczynski12 Aleksander Sadowski3 , Frederic A. Rasio4 , Tomasz Bulik 5
Footnote 1: footnotetext: Statistics is much better for single stars than binaries; and even with only \(2\times 10^{5}\) single stars we obtain usually thousands, and minimum severa... | [] | |
a realistic mass spectrum) have yet to be performed. For old and relatively small systems (such as small globular clusters), complete evaporation is likely (with essentially all the stellar-mass BHs ejected from the cluster through three-body and four-body interactions in the dense core). This is expected theoretically... | [] | |
can drive rapid collisions and mergers of massive main-sequence stars during an early episode of cluster core collapse (Freitag et al. 2006a,b). Instead, our results can provide highly realistic initial conditions for dynamical simulations of dense star clusters in which the early phase of massive star evolution procee... | [] | |
given system. Masses of single stars and binary primaries (more massive components) are drawn from the three-component, power-law IMF of Kroupa, Tout, & Gilmore (1993) (see also Kroupa & Weidner 2003) with slope \(\alpha_{1}=-1.3\) within the initial mass range \(0.08-0.5{\,M_{\odot}}\), \(\alpha_{2}=-2.2\) for stars w... | [] | |
are disrupted when a high-magnitude kick occurs. Finally, the single BHs formed through binary mergers have the lowest (nonzero) velocities (\(\sim 10-100{\,{\rm km}\,{\rm s}^{-1}}\)), since they are the most massive BHs and therefore most affected by fall-back.
In Figure 3 we show the velocity distributions at a late... | [] | |
from the property that tighter BH progenitor systems experienced at least one RLOF/CE episode leading to orbital decay, while wider systems never interacted and stayed close to their initial periods. The two peaks are clearly separated with a demarcation period \(P_{\rm s}\sim 10^{3}\,\)d.
It is easily seen here that ... | [] | |
The model I distribution is slightly different, especially at early times when most BHs form with no kick, since in this model we consider only the most massive BHs formed mainly through direct collapse.
A few models show more significant differences. Different metallicities lead to changes in BH velocities, especiall... | [] |
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