An investigation of the structure of non-uniformities of interstellar absorption using photometry of globular clusters

Gerashchenko, A. N.; Kadla, Z. I.

doi:10.1080/1055679031000110867

Cited by 4 publications

(3 citation statements)

References 2 publications

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“…Valenti et al (2007) and Chun et al (2010) studied this cluster in the infrared JHK bands. The presence of differential reddening has been previously noted, and Gerashchenko & Kadla (2004) mapped the extinction towards the central region of the cluster (see Figure 33).…”

Section: Ngc 6235 (Figure 10)supporting

confidence: 64%

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Uncloaking Globular Clusters in the Inner Galaxy

Alonso-García

Mateo

Sen

et al. 2012

The Astronomical Journal

120

100

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Extensive photometric studies of the globular clusters located toward the center of the Milky Way have been historically neglected. The presence of patchy differential reddening in front of these clusters has proven to be a significant obstacle to their detailed study. We present here a well defined and reasonably homogeneous photometric database for 25 of the brightest Galactic globular clusters located in the direction of the inner Galaxy. These data were obtained in the B, V, and I bands using the Magellan 6.5 m Telescope and the Hubble Space Telescope. A new technique is extensively used in this paper to map the differential reddening in the individual cluster fields, and to produce cleaner, dereddened color-magnitude diagrams for all the clusters in the database. Subsequent papers will detail the astrophysical analysis of the cluster populations, and the properties of the obscuring material along the clusters' lines of sight.

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Section: Ngc 6235 (Figure 10)supporting

confidence: 64%

“…Previous work using ground-based data includes that of Rosenberg et al (2000a) in V I, and Gerashchenko & Kadla (2004), Contreras et al (2005) and Contreras et al (2010) in BV . Beccari et al (2006) studied this cluster using a combination of BV I (ground) and U 255 U 336 V 555 (space) bands.…”

Section: Ngc 6235 (Figure 10)mentioning

confidence: 99%

Uncloaking Globular Clusters in the Inner Galaxy

Alonso-García

Mateo

Sen

et al. 2012

The Astronomical Journal

120

100

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“…This globular cluster is located relatively close to the Galactic plane (b = −9. • 88) and suffers from reddening of E(B − V ) = 0.34 (Gerashchenko & Kadla 2004). Images of NGC 4372 were obtained on 14 nights in 2004 and on 5 nights in 2005 (Fig.…”

Section: Ngc 4372mentioning

confidence: 99%

Cluster AgeS Experiment (CASE): deficiency of observed dwarf novae in globular clusters

Pietrukowicz

Kałużny

Schwarzenberg‐Czerny

et al. 2008

Monthly Notices of the Royal Astronomical Society

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We present the results of a search for dwarf novae (DNe) in globular clusters (GCs). It is based on the largest available homogeneous sample of observations, in terms of the time‐span, number of observations and number of clusters. It includes 16 Galactic GCs and yielded two new certain DNe: M55‐CV1 and M22‐CV2. All previously known systems located in our fields were recovered, too. We surveyed M4, M5, M10, M12, M22, M30, M55, NGC 288, NGC 362, NGC 2808, NGC 3201, NGC 4372, NGC 6362, NGC 6752, ω Centauri (NGC 5139) and 47 Tucanae (NGC 104). The discovery of two DNe, namely M55‐CV1 and M22‐CV2, was already reported by Kaluzny et al. and Pietrukowicz et al., respectively. In the remaining 14 GCs, we found no certain new DNe. Our result raises the total number of known DNe in the Galactic GCs to 12 DNe, distributed among seven clusters. Our survey recovered all three already known erupting cataclysmic variables (CVs) located in our fields, namely M5‐V101, M22‐CV1, and V4 in the foreground of M30. To assess the efficiency of the survey, we analysed images with inserted artificial stars mimicking outbursts of the prototype DNe SS Cygni and U Geminorum. Depending on the conditions, we recovered between 16–100 per cent of these artificial stars. The efficiency seems to be predominantly affected by duty cycle/time‐sampling and much less by distance/magnitude. Except for saturated tiny collapsed cores of M30, NGC 362 and NGC 6752 (and also the dense core of NGC 2808), crowding effects in the V band were avoided by our image subtraction technique augmented with auxiliary unsaturated B‐band images. Our results clearly demonstrate that in GCs common types of DNe are very rare indeed. However, great care must be taken before these conclusions can be extended to the CV population in GCs.

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Differential reddening in 48 globular clusters: An end to the quest for the intracluster medium

Pancino,

Zocchi,

Rainer

et al. 2024

A&A

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For decades, it has been theorized that a tenuous but detectable intracluster medium should be present in globular clusters, which is continuously replenished by the gas and dust ejected by bright giants and periodically cleared by interactions with the Galactic disk. However, dedicated searches, especially in infrared and radio wavelengths, have returned mostly upper limits, which are lower than theoretical expectations by several orders of magnitude. We profited from recent wide-field photometry for 48 Galactic globular clusters to compute high-resolution maps of differential reddening, which can be used to correct any photometric catalog in these areas for reddening variations. Using 3D reddening maps from the literature, we evaluated the amount of foreground extinction. This allowed us to estimate the masses of the intracluster medium in our sample clusters, with an accuracy of one order of magnitude. Our estimates agree with the few available literature detections and with theoretical expectations. Because the discrepancy between observations and expectations only concerns literature upper limits, we explored possible reasons why they could be underestimated and we show that two recent discoveries can explain the discrepancy. The first is the recent discovery that the intracluster medium in 47\,Tuc is not centrally concentrated. This is also supported by our maps, which in the majority of cases do not show a central reddening concentration. The second is the discovery that the dust in metal-poor Fe/H \,lesssim \,$-$1\,dex) globular clusters is dominated by iron grains rather than silicates, which undermines previous dust mass estimates from observed upper limits. We conclude that current evidence, including our maps, does not contradict theoretical expectations and the problem of the missing intracluster medium is no longer an issue.

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An investigation of the structure of non-uniformities of interstellar absorption using photometry of globular clusters

Cited by 4 publications

References 2 publications

Uncloaking Globular Clusters in the Inner Galaxy

Uncloaking Globular Clusters in the Inner Galaxy

Cluster AgeS Experiment (CASE): deficiency of observed dwarf novae in globular clusters

Differential reddening in 48 globular clusters: An end to the quest for the intracluster medium

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